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ENFORCEMENT WORKSHOP ON
PLANT INSPECTION AND EVALUATION
Volume VIII
Complaint Investigation Procedures
Prepared by
Gary L. Saunders
PEDCo Environmental, Inc.
505 S. Duke Street
Durham, North Carolina 27701
Contract No. 68-01-4147
P/N 3470-1-CC
Prepared for
U. S. ENVIRONMENTAL PROTECTION AGENCY
Division of Stationary Source Enforcement
Office of Enforcement
Washington, D. C. 20460
Draft
August 1979
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COMPLAINT HANDLING AND ODOR INVESTIGATIONS
One of the agency responsibilities often delegated to the
field inspector is that of complaint handling and investi-
gation. The inspector may be required to expend a considerable
effort in investigating complaints because of the types of
local industry. Other factors which affect the number of
complaints an agency receives include density of the general
population and industry in a given area, area topography,
weather conditions and the attitudes of the people and source
operators in the local area. When investigating complaints the
field inspector must realize that human emotions and subjective
evaluations come into play and that it is important for the
inspector to remain as objective as possible and obtain all the
facts pertinent to the complaint being investigated.
An agency must expect to be confronted with all types of
complaints; noise, water, air, and some that probably are more
adequately dealt with by the social services department. This
paper will be concerned with the procedures necessary for the
investigation of air pollution complaints, primarily odor
complaints. The investigation of odor complaints probably
provides the best example of the procedures necessary to
properly determine the location of the source, frequency, and
magnitude of the problem causing complaints.
One or more of the following three general areas usually
provoke complaints: 1) visible emissions, 2) odors, and 3)
atmospheric conditions, i.e., smog and low visibility which may
irritate eyes and throats. The inspector usually has little
control over atmospheric conditions and therefore may only be
able to give advice to minimize exposure. Complaints con-
cerning visible emissions and opacity violations are usually
"easier to investigate because a source is usually easily
located. However, the investigation of complaints concerning
odor may require more effort because pinpointing the location
of the source or emission point may be difficult.
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The inspector should realize in receiving a complaint that
the complainant may be irrate, frustrated and subjective in
their evaluation of the situation. Perhaps the best thing the
inspector can do is to let the complainant explain the
situation uninterruptedly to "get it off his chest". Once the
complainant is finished, some questions which may not have been
answered may be asked, such as:
1) Where do you think the problem is coming from?
2) How long has this been occurring?
3) Have there been other incidents? and most importantly,
4) Is the problem occurring now?
Other important information which should be recorded is the
name and address of the complainant, the time and date the
complaint was received, and any other information which will
enable the inspector to determine the source. This assumes, of
course, that the complaint is received directly by the agency
by telephone from the complainant. Receiving the complaint by
other indirect methods such as referral by another agency or by
mail may eliminate the ability to ask the questions above and
obtain immediate answers. The first paper in this volume by C.
Gurber discusses some of the generalities of complaint
handling.
It is probably in the best interest of the agency and the
field inspector to respond to each complaint as soon as
possible. Some agencies may have established protocol or
guidelines which should be routinely followed for complaint
handling by field personnel. By responding to each complaint
the agency gains a certain degree of respect from the public
sector as being concerned or "doing their job". An agency
which fails to respond satisfactorily to citizen complaints may
appear apathetic to the public viewpoint or interest.
The form of the agency response will probably depend, in
part, on the nature of the complaint. A complaint received by
mail may require a followup telephone call or visit to obtain
additional information. If the agency is aware of which source
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is causing a problem, why the situation is occurring, and how
long it will take to correct the problem, the field personnel
.may advise the complainant(s) of this by phone or mail.
Complaints received by phone directly from a complainant will
probably require either a personal visit or a response by
phone. The most time consuming of the two is a visit to the
complainant(s) although it may also provide the most informa-
tion from first-hand observation of the situation.
As mentioned previously, odor complaints are perhaps more
difficult to handle than those associated with visible
emissions. Odors may be associated with visible emissions but
generally a complaint about visible emissions is usually one
concerning visibility. Odors, and the complaints they
generate, tend to be more difficult to handle because the
observations made are usually subjective. It is the respons-
ibility of the field inspector and other agency personnel to
remain as objective as possible. Unfortunately, there is no
reliable objective method to evaluate all odors such as some
type of instrumentation. However, the field inspector should
be trained to evaluate odors in a manner analygous to the
method an inspector is trained, to observe visible emissions
(EPA Method 9). This training should include:
1) Objective evaluation of odors, including identifi-
cation of odors and intensity of odors,
2) Relating odors to the inspectors own level of
sensitivity and to that of the general population,
and
3) Knowledge of the types and magnitude of biases which
can occur in the field.
With this training the field inspector should be able to assess
the frequency and magnitude of an odor problem and establish
the existence of a public nuisance. The field inspector should
--also be able to identify the source or sources that are
producing an odor problem. After gathering evidence and data
the inspector should then proceed with whatever action is
necessary to resolve the problem.
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Characteristics of Odors
Even under the best conditions the investigation of odor
complaints is still quasi-objective. However, with training,
the inspector can become familiar with the biases which may
occur when "quantifying" odors. This is important, not only
for first-hand observations, but also for obtaining information
from the complainant to provide an indication of the source of
the problem.
It should be realized that an odor is not a contaminant
but merely a characteristic of a substance. The substances or
contaminants which cause odors are called odorants. Nearly all
substance "have an odor" although the sensitivity to odors is
highly variable between individuals and various physiological
and psychological factors bias this sensitivity. The "strength"
of an odor appears related to the volatility and chemical
reactivity of the compound. Compounds with higher vapor
pressures tend to "give off odors" more readily than those with
low vapor pressures. Familiar odors which most people can
identify through mental association (e.g., coffee, skunk, moth-
balls, paper plants, "new car") are termed characteristic odors
and are useful in investigation of odor complaints. There are
many odors whose qualities people are familiar with although
they are not familiar with the odorant itself.
The field inspector will find the following parameters
useful in the objective evaluation of odors:
1) Quality,
2) Intensity,
3) Acceptability, and
4) Pervasiveness.
(1) Quality
The quality of an odor may be described in terms of
familiar or unfamiliar odorants. Odors may actually affect
senses other than smell and appropriate modifiers may be added
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to describe odor quality. However, description of odors
(terminology) is fairly meaningless without formal training and
exposure in training courses. There are several classification
systems (examples of some are found in the article by Gruber,
(Paper 2 in the-attachment) but none seem to have a clear
advantage over the others. These classification systems do
provide the basis for an odor vocabulary.
(2) Intensity
The intensity of the odor refers to the relative strength
of an odor. The strength of an odor may be given a numerical
designation (analogous to Ringlemann numbers used for visible
emissions evaluations). The evaluation of odor intensity
should be made without consideration of the acceptability of
the odor. This allows for a more objective evaluation of the
odcr. nuisance.
(3) Acceptability
Acceptability of an odor is a subjective determination by
the field inspector. The acceptability of an odor may be
influenced both by the intensity and quality of an odor. For
example, an odor may be described by both its intensity and
quality. If this odor is a familiar one, it may be acceptable
at one intensity and unacceptable at another. It may even
appear to change quality at different intensities.
(4) Pervasiveness
The pervasiveness of an odor refers to the tendency of an
odor to remain undissipated by dilution. The pervasiveness is
related more to the odorant and its characteristics and not to
the odor itself. The pervasiveness is generally found by
experiment only.
--Odor Perception
The mechanism by which the sense of smell operates is not
thoroughly understood and in many cases the detection of an
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odor may be the result of stimulation of more than one of the
senses (e.g., formaldehyde tends to have a sweet smell and
burns the eyes). Although an odor is a characteristic property
of an odorant, the perceived odor is interpreted by the human
nervous system and may be biased by the observer's nervous
system and brain. This may help explain some of the observed
differences in odor perception and reporting. Some other
factors that may cause biases in the reporting of odors are:
1) An unfamiliar odor may be more likely to cause
complaints than a familiar one;
2) Olfactory fatigue may occur after continuous exposure
to an odor;
3) An odor is usually perceived after there has been a
significant change in odor quality or concentration;
4) Odor quality may change upon dilution;
5) There is a daily variation in a persons ability to
detect odors;
6) The perception level of odors decreases with
increasing humidity. However, high humidity tends to
concentrate odors in a given locality; and
7) Some persons can detect certain odor qualities but
not others.
As may be seen above, physiological factors play a key role in
the perception abilities of an individual as well as psycho-
logical factors. Some attempts have been made to mechanically
sense odors through use of various monitors. This, of course,
would provide a completely objective evaluation of the
concentration of a given odorant. Unfortunately, these
instruments are not completely successful because they are
usually chemical (odorant) specific and are subject to many
other interferences and biases. The field inspector, on the
other hand, may observe and evaluate many odorants at once and,
if properly trained to know what biases influence him, may make
an evaluation as to the severity of the problem. Other than
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proper training, there is little that can be done to remove the
remaining subjectiveness of the field inspector's evaluation.
However, the field inspector has a tremendous advantage over an
instrument in that he can obtain a great quantity of informa-
tion concerning the conditions he is there to investigate and
evaluate it quickly. In short, the inspector can think while
an instrument cannot.
Since the field inspector is subject to numerous biases,
both physiological and psychological, there are several items
that should be recorded in investigating odors. These include:
1) Identification of the odorant and concentration,
2) Ambient conditions, and
3) The status of the inspector or observer.
By documenting these points the inspector documents the
conditions which may affect the inspector's evaluation of the
situation. This documentation should alert the field inspector
of the type of biases which may occur given the current
conditions.
In identifying an odorant the field inspector must rely
upon training and his knowledge of the potential odorants in
his or her area. The ability to identify an odorant should be
considered an asset. However, the field identification of an
odor is generally limited and the field inspector must rely
upon odor quality to establish the source of the odorant.
Odors from chemically unrelated compounds may often be very
similar whereas odors from chemically similar compounds may be
very dissimilar. The intensity of an odor is related, in
general, to the ambient concentration of the odorant, and as
mentioned previously, the odor quality may be influenced by the
ambient concentration.
If the odorant has been identified, the concentration may
be determined by relating the field inspector's sensitivity to
"that of a statistically significant number of people. This may
be done by dilution techniques where a sample is taken and
diluted to the inspector's detection threshold. This detection
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threshold for any given odorant is highly variable from person
to person but the detection threshold compared to both the
value for the observer/inspector and the statistically derived
value. Once the detection threshold and dilution value is
known the original concentration may be calculated. These
techniques are discussed in the paper by Huey et al., Paper 6,
found in the attachments.
Thus far, the discussion has been applicable to an
individual compound or odorant. The situation becomes more
complex when discussing mixtures of odorants. Odor quality may
be highly variable because the proportions and dilutions of the
odorants may vary with time. Furthermore, one cannot predict
what effect or perceived intensity a mixture of odorants can
produce. There will be some instances where the effect is
simply additive. But other possibilities include:
o Synergistic, where the observed intensity is greater
than would be expected-for an additive affect.
o Conteractive, where a "cancelling out" affect is
observed and the intensity is less than what would be
expected for one odorant alone.
o Suppressive, where the observed intensity is less
than what would be expected additively but greater
than any one odorant alone.
Although the odorants in a mixture may remain identified and
their concentrations remain unknown, it may be possible to
identify the source by some characteristic odor.
Ambient conditions may affect the quality and perceived
intensity of an odorant or odorants. The magnitude of these
effects have not been studied in depth to determine what biases
are involved. However, any laboratory evaluation should be
conducted as close as possible to field conditions to yield
comparable results.
The physiological and psychological status of an observer
when combined with ambient condition effects may act to
introduce a large variation in the perceived quality and
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intensity of an odorant. Some parameters which are of
importance are:
1) The sensitivity of the field inspector to a given
odorant compared to a statistically significant
number of observers;
2) The training of the field inspector to detect and
discriminate odors. This is limited in part by the
sensitivity to the odorant, although a trained person
is likely to detect smaller changes in intensity than
an untrained person; and
3) The condition of the observer. For example,
olfactory fatigue sets in after long exposure to
odors. This decrease in sensitivity appears to be
related more to length of exposure rather than to
high intensity. Quantification of this effect is
difficult because of the variation between persons.
Other physical conditions such as colds, sinus
infections, etc., may influence the ability of the
observer to evaluate the situation. Psychological
factors will probably be more difficult to "quantify"
but may be influenced by physiological conditions and
attitudes.
Odor Source Identification
In the investigation of odor complaints it will be
necessary to move towards the resolution of the problem. This
will necessitate the identification of the problem source. The
simplest procedure is to triangulate back from the wind
direction through the source or sources which may be causing
the problem. This may require a number of observations on
different days to pinpoint the source in areas where there are
a number of potential sources. The paper by Huey et al. (paper
.number 6 in the attachment) discusses some of the techniques
which may be used to determine an odor source. An important
consideration, particularly when a course of litigation is
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chosen to resolve the odor problem is for the inspector to go
upwind of the suspected source to confirm that the odor did not
exist on the upwind side of the source.
Controlling an Odor Problem
This paper 'will not discuss the control techniques which
are available to control odors, but will discuss some of the
options usually available to the field inspector. Very often
after the source has been identified and the plant operator/
manager sees the evidence gathered, the' plant will take steps
to abate the problem. In a small percentage of cases there
will be some sources which will resist the effort to control
the problem. Some of these will finally respond if they feel
that the evidence is overwhelming and some will fight "tooth
and nail" all the way into court. Generally, when litigation
is involved it centers around the establishment of a public
nuisance. The field inspector and agency must determine the
magnitude of the problem in terms of the number of persons
affected. The agency cannot solicit complaints from the
citizens to justify a case but may only report their observa-
tions and the information obtained from their complaint
observations.
Other methods of encouraging a source to come into
compliance are fines for violations of regulations. Such
regulations are usually written in broad language such as "No
source shall cause, suffer, allow or permit to be emitted any
odorous substance to be discharged without employing suitable
measures for control odorous emissions". Another method of
encouraging the source into compliance is the possibility of
revoking or not renewing the source's operating permit. These
actions tend to strain the relationships between the source and
the field inspector. Fortunately, such cases are in the
-minority.
In summary, the method in which an inspector conducts
complaint investigations reflects not only on the inspector but
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also on the agency. Complaint investigations which are handled
in a competent, objective, and professional manner will gain
the inspector and the agency the respect which is vital to the
everyday operation of both the field inspector and the agency.
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PAPER 1
COMPLAINT HANDLING
BY
C. GRUBER, CONSULTANT
(Adapted from APTC-1100 Field Operations and Enforcement
Manual for Air Pollution Control, Volume I.)
Reprinted from revised training material for Air Pollution
Institute Course 1444.
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COMPLAINT HANDLING
I. INTRODUCTION
Responding to citizen complaint of ^T pollution nuisance is an
important task of the FED. It often can be time consuming with
great difficulties in legal prosecution, should such procedure
be necessary to secure abatement of a public nuisance.
II. PUBLIC NUISANCE, LEGAL ASPECTS
The inherent responsibility for enforcement against public
nuisance starts with state and local statutes. A typical regula-
tion might read:
" No person shall discharge from any source
whatsoever such quantity of air contaminants or other
material which cause injury, detriment, nuisance or
annoyance to any considerable number of persons or
to the public "
The legislative intent is quite clear that'no one should cause a
public nuisance. A "considerable number of persons" which defines
the public nuisance in the foregoing regulation has not been defined,
and therefore is vague and causes problems of enforcement of the
nuisance regulations. Some agencies have given as a rule of thumb,
"ten separate households" as defining "considerable number" and
then proceed with less if the situation is very bad, or requires
more if the nuisance is marginal.
An emission that affects only one person is a private nuisance and
is not subject to prosecution under the above quoted statute.
However, the agency has a responsibility to respond to all nuisance
complaints, Including those from a single complainant, and should
attempt to alleviate the nuisance situation. A single individual
who suffers a nuisance is free to take legal action, seeking
damages or Injunction, against the suspected source. In such an
action, the enforcement officer may be called as a witness to
testify to the extent or effect of the nuisance.
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III. CAUSES OF NUISANCE COMPLAINT
To assist the receiving operator, a list of typical situations
which cause complaints could "be posted and referred to as a
helpful guide. Complaints are triggered "by one or more .of the
following:
* Offensive odors.
* A specific violation, most probably opacity.
* Large particle fallout, easily visible on
porches, lawn furniture, and plants, etc.,
but difficult to identify the source.
* Fugitive dust from construction or demolition.
* Plant or materials damage.
* Fugitive dust from industrial source.
* Episodal release affecting health.
* Open burning.
* General conditions such as "The air is awful
today, my eyes bum, throat is sore, etc."
IV. RECEIVING A COMPLAINT
A complaint of nuisance is transmitted to the agency by telephone,
by letter, by personal visit or referral from a central reporting
agency for all types of citizen contacts.
Most serious complaints are phoned in to a receiving clerk of the
agency who should be trained and experienced in processing such
calls. Often the caller is irritated and emotional, rather than
factual. Under such circumstances, the caller should be allowed
to talk himself out, and then questioned to get the facts the
operator needs for proper dispatching of the FEO.
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An agency might prepare a form which includes the Information needed
from the caller. A list of questions helpful to the operator would
include:
* What is your full name, address and phone number?
* What is the condition complained of?
* Where do you think it is coming from?
* Is it going on now?
* When did it start?
* Have there been other occurrences?
Get specific dates and times.
* Is anyone reported getting sick?
* Are other people bothered?
* Listen for other specific data related to the event.
The complaint from should include the date, time and name of person
taking the complaint and time of dispatch.
After the message log is completed, a complaint number is assigned,
the time is stamped on the log and a field enforcement officer is
dispatched immediately to the scene. Complaints are investigated
as speedily as possible to ensure that the reported source may be
reached while the violation or nuisance is still in progress.
V. COMPLAINT INVESTIGATION.
If he works in a district, the FED may already know much of the
background of the source. However, he should check the source
file to obtain the recent history.
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Upon arrival In the vicinity, the enforcement officer first observes
the alleged source to determine if a violation is involved. If a
violation is observed, he investigates, writes and serves a notice,
if warranted. Then he visits the complainant. However, if no
violation is immediately apparent, the complainant is 'contacted.
Some agencies will have the FED first contact the complainant, then
proceed to the suspected source for investigation. Either this
procedure or the above is acceptable.
A. Complainant Interview
The enforcement officer makes every effort possible to avoid
obvious identification of the complainant. He is particularly
careful not to park his official vehicle too close to the
complainant's residence should the complainant and the source
be near each other. The identities of all complainants should
be considered to be confidential and should not be disclosed to
anyone who is not an employee of the enforcement agency.
If the complainant is not at home the enforcement officer should
leave a message. If the complainant is at home, the enforcement
officer identifies himself by name and agency in a friendly manner,
and proceeds with the interview.
The enforcement officer is friendly, but dispassionate. He
generally employs a "non-directive" interview technique in that
he allows the complainant to get the matter off his chest so
that the facts of the situation can be calmly discussed. He
should also appreciate the fact that a person who is angry
may be honestly motivated by a serious or chronic tvVr pollution
condition.
In permitting the complainant to speak his mind, it is well for
the enforcement officer not to interrupt. It is particularly
effective, however, that when facts appear the officer repeats
them aloud for verification and then writes them down.
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After the complainant has expressed himself, the enforcement
officer then proceeds on a. line of questioning •which will (l)
determine the cause of the complaint and (2) the nature and
source of the a-i-r pollution problem cited in the complaint.
The line of questioning in this case is intended to complete
and verify the data supplied by the complainant.
The cause of the complaint may not always involve air pollution.
Although most complaints are justified, some will concern problems
over which the agency has little or no control and in which air
pollution may play a minor role. These concern "backyard feuds,
natural contaminants, resentment towards a nearby company or low
concentrations of contaminants which may affect illness or allergy
in an individual. Although the enforcement officer may have no
legal powers in such cases, he thoroughly investigates and attempts
to correct all air pollution problems. If such complaints are '
unsubstantiated, he establishes the cause of the complaint and
documents the fact that no violation has occurred by recording
the operational data of the equipment at the alleged source.
The Information given by phone is checked and enlarged to include
the following:
* Name and location of source complained of.
* Frequency of annoyance or occurrence of plume.
* Time of day nuisance was first noticed.
* Duration of nuisance at each occurrence.
* Names and addresses of persons affected.
* Location and extent of property damage, if any.
* Description and frequency of any illness alleged to
have resulted from the air contaminants.
* Description of odors or any other pollutants that may
be involved.
* Any other Information the complainant may have that
will relate the nuisance to a specific piece of equipment.
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In an air pollution problem which appeaxs to involve toxicity, the
enforcement officer records all observed or reported symptoms
such as:
nausea eye tearing
vomiting soreness of throat
headache nasal discharge
eye-irritation turning "blue
fever cough
constriction of chest difficulty of "breathing, etc.
If the symptoms appear serious, a physician and the health authorities
should "be contacted. The enforcement agency should also be immediately
notified in order that an emergency vehicle may be dispatched to the
scene to measure the concentrations of any possible toxic contaminant.
It should be noted that only a physician can make a diagnosis. The
enforcement officer records reported symptoms In his report. The
enforcement officer can note the name of the physician conducting
the diagnosis and treatment. This information is important if
public nuisance action should be initiated.
While interviewing complainants, the enforcement officer does not
promise legal action nor does he commit himself or the control
agency to any course of action. He should, however, explain to
the complainant the laws involved and the evidence required to
instigate legal proceedings. But he will also explain that he will
first attempt to seek cooperation on the part of those who may be
responsible.
If odors, soiling or other property effects are involved, the
enforcement officer examines the citizen's property. The pattern
of fall-out of contaminants may indicate the direction from which
they cane. If a malodor is detected at the complainant's property,
the wind direction can be determined for the purpose of tracing the
odor to its source.
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Qiite often the job is completed if the complaint or nuisance
also involves a violation of the rules and regulations through
the emission of contaminants in excess of that allowed, or
through the operation of unpermitted equipment, or through
operation of equipment contrary to permit conditions. In
I these instances, the action to "be taken is indicated.
If, however, the nuisance is a result of quantities of air
pollution which are allowed by quantitative standards in the
Rules and Regulations, a public nuisance will have to "be proven.
When the enforcement officer contacts the plant operator, he
explains that he is investigating a complaint, unless, in the
individual instance it should be strategic not to do so. The
enforcement officer may also explain that he is trying to
determine whether or not the complaint is justified. This
gives management the opportunity to state its case, since it
knows that the enforcement officer is not yet committed to any
action. As with the complainant, he is also attentive and
takes notes. Then, on the basis of the information he acquires
from the complainants, he asks developmental questions and
completes the story. He then inspects the equipment and compares
actual operating conditions, cycles and times of operation with
the times and frequencies of complaints.
VI. RESOLUTION OF THE NUISANCE
Because the enforcement officer is an indifferent observer between
two parties in conflict, he has a natural tendency to act as
mediator and will attempt to find that solution to a problem
which will satisfy both the complainant and the operator.
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After the problem is Identified and the specific source is
isolated, means of abatement may then "be determined. If the
problem was a single occurrence, it probably was not anticipated,
was perhaps caused by a breakdown, a fire, a power shortage or
some other situation equally unforeseen. The chances of this same
Incident happening again are slim, preventative action unlikely,
and corrective measures unnecessary except to repair or compensate
for damages. Where the problem is operator error, then it becomes
the company's responsibility to ensure that personnel are adequately
trained.
When the problem is continuing or recurrent, then it becomes
critical to eliminate the cause. Occasionally, an improved
regular maintenance program will abate the problem, either by
reducing the likelihood of a breakdown or by preventing a buildup
of material causing fugitive dust or odor emissions.
Sometimes the problem can be solved by altering the operation or
yrocess somewhat, without actually altering the equipment. This
may involve changes in the processing rate or throughput, changes
in operating conditions such as temperature, or changes in material
being processed. Relocation of the equipment within the plant
premises may also solve the problem. Ideally, when the equipment
is first put into operation, those operating conditions which could
cause a public nuisance should be anticipated. Restrictions or
conditions can be imposed on the operating permit limiting the
operations to that which will not cause a nuisance.
The most common solution involves replacing the basic equipment with
newer, more air pollution efficient equipment or the installation of
adequate control equipment. After-burners, adsorbers and scrubbers
have all been used successfully to reduce odors; electrostatic
precipltators, cyclones and scrubbers have been effective with
particulate matter.
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As a rule, enforcement officers do not solicit opinion in a
neighborhood regarding the "behavior of any plant, "but confine
themselves to those persons volunteering complaints. It is
usually citizens who do the canvassing and who supply the informa-
tion. The enforcement officer may then interview all complainants
involved. The canvassing of complainants is usually discouraged.
The enforcement officer does not sample, nor act on, opinion, "but
on sincerely motivated complaints. The canvassing of the neighbor-
hood can "be construed in a court of law as "being prejudicial to the
plant.
The enforcement officer, on the "basis of his knowledge of air
pollution, however, evaluates the consistency, correspondence and
intensity of remarks made "by possible witnesses. He attempts to
find some degree of unanimity regarding the objectionability of
the problem among those who might be equally affected. Diverse
opinions and inconsistencies are first signs that a public nuisance
case may not be easily developed.
B. Inspection of the Source
Prom the facts gathered so far, the enforcement officer may have
a notion of the specific or type of source responsible, especially
if he has identified contaminants and has observed definite
evidence of damage or detected odors on the complainant's property.
In other cases, he may know the identity of the contaminants, but
not the source of origin. In still other cases, the contaminants
may be completely unknown.
To establish a public nuisance, a source within a certain facility
responsible for the offending emission must be proved. In some
cases, the equipment involved may be obvious; in others, especially
in a plant containing many pieces of equipment, the source may be
difficult to locate. In the latter instance, each piece of equip-
ment must be inspected in detail. Those which do not contribute
to the problem are eliminated from consideration.
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VII. ENFORCEMENT
The most difficult type of air pollution case is the public nuisance.
A public nuisance frequently occurs when a number of persons are
annoyed by a quantity of contaminants which is otherwise allowed.
The problem in cases of alleged public nuisance is to determine
whether a private dispute or a valid public dispute is involved.
If a private dispute is involved, then the citizen must initiate
his own legal action. A public nuisance, however, involving a
"considerable number of persons" or a reasonable cross-section of
the immediate community affected is handled as an enforcement action.
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PAPER 2
ODOR POLLUTION FROM THE OFFICIAL'S VIEWPOINT
by
C. GRUBER, CONSULTANT
@Copyright by American Society of Testing and Material (1954).
Reprinted with permission from the American Society of Testing
and Materials 57th Annual Meeting, (Chicago, June 15, 1954),
ASTM Technical Publication No. 164, P. 56, (1954).
27
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ODOR POLLUTION FROM THE OFFICIAL'S VIEWPOINT
BY CHARLES W. GRUBER'
This paper will attempt to point out
the perplexity of the outdoor odor pollu-
tion problem and the difficulty en-
countered by the official in dealing with
industry and the public in this matter.
The odor situation is not so difficult to
handle when the source is a well-defined
continuous process running day in and
day out so that the odor pollution level
rises in a particular neighborhood with a
degree of regularity whenever the
weather influences are right—that is,
when a straight flowing air stream
carries the pollutants in a well-defined
fan-like directional pattern to the af-
fected neighborhood downstream horn
the plant or when a stagnant air mass
forms under a low level temperature
inversion layer, causing the pollutants to
mushroom over an entire area. However,
when the offending source is a one- or
two-batch process from among many or
when different materials processed
through the same equipment result in
foul smelling discharges one time and
perfumed fragrance another so that the
odor emissions arc spasmotic, catching
or missing weather conditions to cause
odor build-up without pattern or cyclic
recurrences, it is harder to analyze the
situation than to pick out the shell that
covers the pea at the carnival.
When process operators receive a call
about an odor situation, they can change
the process a little and then deny all
1 Chief Smoke Inspector, Bureau of Smoke
Inspection, Cincinnati, Ohio.
responsibility for the odor source and
defy the .official to find out where it
came from and what caused it. When an
accusing finger is pointed to the plant as
the source, the retort is, "Who, me? I
don't smell anything." Not all do this,
but there are some plants that do.
Local ordinances usually declare
strong and obnoxious odors to be a
nuisance and the emission of such odor
to be unlawful. The wording of the
Cincinnati Ordinance is quoted as
follows:
Section 2501-3(1).—Acid or other fumes,
noxious gases, strong orlors, dust, dirt, or
other solids in quantities (defined in Section
2501-5) emitted or allowed to escape in
such place or manner as to cause injury,
annoyance or detriment to the public, or
to any person or to endanger the health or
safety of such a person or the public, or
emitted in such a manner as to cause injury
or damage to business or property, are
hereby declared a nuisance, and the emis-
sion or escape thereof from any stack, or
chimney, window, door or other opening,
ventilating device, or from any building,
premises or other source, shall be unlawful.
In spite of the fact that most ordi-
nances establish a legal definition of the
odor nuisance, it is a matter of general
experience that for every complaint that
finds its way into the courts, cither as a
private suit in equity or initiated by
public officials as a violation of a specific
statute, probably 1000 are handled by
an air pollution control official and the
29
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GRUBER ON ODOR POLLUTION
offending company on a cooperative
basis. Violations of ordinances must be
proved in court, so the problem of pre-
senting odor quality and intensity as a
fact remains to be solved.
Although Cincinnati may 'not have
the largest chemical plants in the world,
its metropolitan area will take second
place to none, in variety and number of
plants. The Directory of Manufacturers
of the Cincinnati Metropolitan Area for
1952 lists the following chemical and
allied products being produced in plants
in this area:
Industrial inorganic chemicals 15 plants
Industrial organic chemicals 19 plants
Drugs and medicines 22 plants
Soap and glycerin, cleaning and
polishing preparations, and sul-
fonatcd oils and assistants 49 plants
Paints, varnishes, lacquers, japans,
and enamels; inorganic color pig-
ments, whiting, and wood fillers. .. 34 plants
Fertilizers 6 plants
Vegetable and animal oils and fats.. 11 plants
Miscellaneous chemicals including in-
dustrial chemical products and
preparations 75 plants
A total of 231 chemical product
classifications are manufactured in this
area. Add to this 6 coffee-roasting
plants, 24 meat-packing plants, 18
plants producing products of petroleum
and coal (roofing felts and coatings,
petroleum refining and paving mixtures,
etc.), 8 rubber products plants, 3 tanner-
ies, 6 breweries, 1 distillery, and Mill
Creek, and one may well realize there
are a few odors around once in a while.
As an illustration of some of the odor
problems encountered in the operation
of the Bureau of Smoke Inspection,
several case histories are cited.
Case No. 1—A Brewer's Grain-Drying
Plant.—This plant purchases spent grain
from several breweries in Cincinnati and
prepares it for animal feed. For more than
25 yr the plant operated in its present loca-
tion in a closely built-up area, discharging
a moist odor of malt and hops from several
rotary steam driers without a voice being
raised against it. In 19-19, the plant installed
a direct-fired grain drier with practically
no vent above the roof. Immediately the
Bureau was flooded with complaints from
the neighborhood of a scorched fat odor.
After several things were tried unsuccess-
fully, the plant, on its own initiative, raised
the stack about 18 ft above the roof. Com-
plaints continued and it was recommended
that about 60 ft be added to the stack in
order to get the gases well above the sur-
rounding neighborhood. The 60-ft stack
extension was installed, and the odor is
now that of popcorn and is spread out over
a considerable area. Complaints immediately
stopped with the second stack extension.
However, like all partial corrections, satis-
fying the neighborhood is temporary, and
last year several calls were received report-
ing unsatisfactory odor conditions. However,
the situation does not appear to be suffi-
ciently serious to require further correction
on this operation at this date.
Case No. 2—An Adhesive Manufacturing
Plant.—One of the products of this plant
is a gasket-scaling compound that uses
bodied castor oil. The raw castor oil is
heated to 400 F and then blown to proper
body. When the process was first installed,
a water scrubber was incorporated. It
quickly became evident that the scrubber
was not effective and, after several attempts
were made to increase the effectiveness of the
scrubber without results, an odor-masking
agent was added. The correction, however,
was still insufficient and the final solution
to this problem was the purchase of proc-
essed castor oil so that the blowing opera-
tion was eliminated. Complaints from this
location have ceased entirely.
Case No. 3—Animal Hide Cooperative.—
The complaint involved was that of a strong
rotten egg odor. The correction was rather
simple in this case, involving merely the
closing up of the room producing the odor
and the adding of carbolic acid. This solu-
tion was not 100 per cent effective, but no
further complaints have been received
within the past two years.
Case No. 4—Partially Incinerated Animal
Remains.—Serious odor complaints were
received from the neighborhood in the vicin-
ity of a hospital that housed a clinical
30
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SYMPOSIUM ON ODOR
laboratory. The original design of the in-
cinerator for the destruction of pathological
waste was not effective. An adequate gas
burner was applied, and now the dogs and
monkeys are burned to a crisp with the
complete elimination of the odor nuisance.
Case No. 5—Asphalt Still— Odor from
the asphalt still of one particular roofing
plant is still a problem even though an
odor-masking agent has been applied. The
results of the odor masking indicate that a
certain degree of improvement has been
accomplished, but it is believed that a more
complete correction must eventually be
applied before the odor situation will be
entirely satisfactory. Progress at this plant
is slow because some years ago a $50,000
pipe line was installed to carry the fumes
from the asphalt still to the boiler house for
use in conjunction with pulverized fuel
burners. The installation was so hazardous
that its use had to be discontinued, but the
stainless steel monument is still in place.
Case No. 6—A CoJfee-Roasting Plant.—
Whereas the odor of roasting coffee is savory
to a passerby, to those living in the neigh-
borhood the odor can become a serious
nuisance, particularly when the coffee roast-
ing is measured in thousands of pounds an
hour. In 1952 and 1953, the old batch type
roasters of this food processing plant were
replaced with continuous roasters 'incor-
porating a high degree of protection both
from carry-over of coffee chaff and from
odor. The odor elimination is obtained by
incineration and is for all practical purposes
100 per cent effective.
Case No. 7—A Varnish-Cooking Plant.—!
In this case, open cookers were replaced
with closed kettles heated by Dowtherm.
Multipass scrubbers were incorporated in
the plant design. The odor pollution, al-
though not 100 per cent eliminated, is
considered satisfactory from periodic ob-
servations of the neighborhood as well as
from lack of citizen complaints.
Case No. 8—A Chemical Plant Producing
Printing Inks, I^acqucrs, Dye Stiifis, and
Pharmaceuticals.—This is the most chronic
case and the most difficult case with which
the Bureau has to deal. Like many plants,
it was at one time out in the country, but
the city has grown up around it. While the
city was growing, the plant also grew and
the combination multiplied the problem
100 fold. Space does not permit a detailed
account of all of the individual items stud-
ied and corrections applied, but a brief
description of the method of dealing with
this case may be of interest since it illus-
trates somewhat the approach that the Cin-
cinnati Smoke Inspection Bureau uses in
dealing with involved odor situations.
The neighborhood was quite tolerant of
the air pollution situation during the period
of World War II, but with the cessation of
hostilities, local hostility became great, and
numerous complaints and written petitions
were filed. In spite of the demand by the
people of the area for legal action by the
city against the company, the Bureau of
Smoke Inspection established a cooperative
program with the company. Because of the
complexity of the situation, Kettering Lab-
oratory of the University of Cincinnati was
asked to assist. They subscribed to the
cooperative program and recommended
against a sampling program in this instance.
Instead, they recommended that the "sniff"
method be employed to evaluate the odor
pollution.
The neighborhood surveys conducted
from time to time will be of interest. The
first survey was made in July, 1950.
Twenty-eight families were interviewed by
two smoke inspectors working from a pre-
pared questionnaire. The results of the sur-
vey were informative but were so varied
that the only positive conclusion that could
be drawn was that a neighborhood pollution
problem existed. Seventeen different odor
descriptions were given including dead fish,
moth balls, rotten eggs, glue factory, pole-
cat, etc.; the most frequent characteristics
given were unpleasant, very strong, nau-
seating, etc.
The majority of the people stated the
odors had been present "since they
moved in"; there was no agreement as
to time of clay when odor was at its
peak but there was general agreement
that odor was worse in hot or foggy
weather. Only 6 reported physical
damage to property. Twenty-six re-
31
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GKUJJHR ox ODOR POLLUTION
ported 11 nil no sickness or ill health was
attributed by their own physicians to
the presence of odors or fumes in the
neighborhood. The detailed results of
the survey are shown in Appendix I.
In September, 1950, these same 28
people were, contacted by letter. The 25
replies arc cataloged as follows:
1. Seven people reported improve-
ment since the last contact.
2. Two people said the air pollution
was worse.
3. Sixteen people said that conditions
were the same.
The September survey indicated that
the situation had not changed materially
and that it was necessary to accelerate
our work with the company. The com-
pany, meanwhile, was tightening its
control, installing scrubbers, absorbers,
changing processes, and improving its
supervision.
During the summer of 1951 periodic
checks were made by inspectors of the
Bureau of Smoke Inspection by a
specific "odor route," and odors were
cataloged and reported to the manage-
ment for corrective action.
A check made in September, 1951, in-
dicated the following reaction: twelve
reported conditions better, four re-
ported conditions worse, seven reported
no change. Again in April, 1952, our
survey indicated the following change
from the previous year: five, better;
two, worse; six, the same. This indicated
that we were holding our own and pos-
sibly making a little progress.
In the summer of 1952, four catalytic
fume burners were installed on the
varnish-cooking processes, and the big-
gest single source of odor pollution was
eliminated. However, another series of
problems developed with the occupancy
of a housing project of 1000 apartments
within one-half mile of the plant and
another 350-unit project about one
mile from the plant. Both projects were
connected to the sewer downstream, and
so added to the air pollution problem
was the sewer odor problem. In 1953,
too, severe drought conditions pre-
vailed to add to the seriousness of the
situation.
An indication of the progress made by
the company by 1953 is the fact that
the regular monthly meetings between
the Bureau of Smoke Inspection and
company officials were dropped for lack
of situations to discuss or programs to
follow. However, there still remains
the operation of the numerous chemical
processes which require considerable
supervision and the ever constant
change from one raw material to another
or from one product to another with a
different or more difficult control prob-
lem always to be reckoned with.
From these case histories, the need
for odor-monitoring equipment becomes
apparent. It is our experience that once
an industry has been shown that an
undesirable condition is brought on by
an effluent from its premises it will
move to correct the situation. The big
question is the completeness with which
the air pollution needs to be removed.
It is at this, point that a system of odor
measurements is sorely needed, particu-
larly one that will assign a number to
represent an odor intensity.
Should this be so difficult? Let us
think for a moment in terms of odor
intensity only and draw a comparison
with the method of evaluating visible
smoke emission. For the measurement
of visible smoke, there is a very crude
scale of visual comparison in the Ringel-
mann chart. Fifty years ago, Professor
Ringelmann2 drew up this crude but
logical method of grading the density of
a visible smoke discharge by its apparent
shadings of gray to black. It permits
JL. C. McCabo, "Atmospheric Pollution,"
Industrial and Engineering Chemistry, February,
1954.
32
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SYMPOSIUM ON ODOR
not only the selection of a legal cutoff
point, but it sets up a number reference
to describe degrees of smoke density. As
crude as it is, the Ringelmann chart has
stood the test of time and has been
adopted almost universally by ordi-
nance writers to assign a number scale
to define the limit of smoke emission.
be readily portable and provide for
rapid results. To make the results
quickly available to the observer, the
odor intensity number result should
show up on a dial; in other words, this
should be a direct reading instrument.
In addition, it should be simple to
operate. The sampling time should be of
FIG. 1.—Odor Chart.
Why can we not take a cue from the
Ringelmann method and develop a
comparative method of odor intensity
measurement, using the nose as the
sensitive instrument? No doubt odor
response is more varied between in-
dividuals than is vision, but the line
need not be drawn so fine. It has been
demonstrated that odor observers can
be trained.
An odor-measuring instrument should
short duration. The goal should be to
arrive at the recognition threshold
rather than the absolute threshold. The
instrument need not be accurate to the
third or fourth decimal place; a scale of
five digits should be ample.
What about odor quality? One of the
greatest difficulties in handling an odor
complaint situation is lack of ability to
get a clear and concise description. We
would expect to get variations in reports
33
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GRUBER ox ODOR POLLUTIOM
FIG. 2.—Route Traveled by Smoke Inspectors.
The circles are potential odor sources. Shaded areas show location of repeated odor complaints.
Inspector "•
Time Storied -•-"'- r- '•'•
Do,, . 9-3-M.
Time Finished 11=15 *• I
WIND
Calr
Csln
:.i-2
Calr.
t-".
t-3
!>-2
Calm
IOCATIOH
Sprint, Crcve
Sl-rtrib Crove
Lala>ette Circle
?.rO I-ja
tartr.ftcr Avjr.ue
t»U- »r..i
Canr^tp
^•jairftn ijr.ci
CarU.a»_e
^.urrB> H^-dQ
V-urru> ara
Sprint, Grove
TIME
9:00
9:CO
9:10
s:;c
?:CC
9:S5
iO:£C
10:40
SUSPKIED
SOURCE
liill Creek
Har.t 7
fl^nt 6
9
Hsr.t 1
rlcr.t 1
Ss».er
FlsM 1
Air Lorr.c
Flai.t 5
Plant 11
COMMON
OFSCRIPIION
I.'!'.! Cr..;k
Fr.cnol
Cool: ir.fe fa:
Mjst>
Li.ar[»
Clinical
Fitl.j
ttrl il izer
hcavj oil
rar.c to
'
UCHHICftl
DESCRIP1IOK
H.,S
Lirr«tl;>l
'
STRENGTH
V3
u
T
T
T
U
M
VS
DESCRIPTION OF ODOR
SENSATION FROM CHART
Fecal
Etherish
Rancid
lftusl>
Sharp
Putrid
Shnrp
Rancid (old taller-)
T-Trace M-Mi!d S-Strong VS - Very Strong
FIG. 3.—Odor Patrol Report.
34
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SYMPOSIUM ON OBOR
TABLE I.—FIRST AREA SURVEY.
Suspected Source
Municipal dump (not
in Cincinnati)
Soap and detergent
manufacturer
Mill Creek
Sewer downstream
from chemical
manufacturing
plant (Case No. 8)
Chemical manufac-
turing plant (Case
No. 8)
Sanitary sewer
Unidentified sources
Composite of all odor
observations
Chart
Name
Burnt or
woody
Musty-
Greasy,
rancid
Sharp
Sweet,
perfume
Oily
Putrid
Putrid
Fecal
Heavy
Warm
Musty
Sharp
Rancid
Burnt,
menthol
Putrid,
menthol
Sour,
musty
Sweet
Rancid
Sharp
Putrid
Heavy
Musty
Burnt
Sharp
Putrid
Heavy
Musty
Fecal
Rubbery
Sour
Etlicrish
Putrid
Musty
Sharp
Burnt
Rancid
Heavy
Fecal
Sweet
Sour
Oily
Woody
Warm
Greasy
Times
Obs."
21
17
16
9
8
6
5
43
15
12
10
9
8
4
4
2
10
9
?
4
10
5
4
15
11
9
7
7
7
4
4
4
74
46
43
30
30
27
21
21
IS
13
13
11
10
Chart
Number
10.5-
11.0
5.5
9.5-7.5
3.0
1.5
8.5
6.5
6.5
7.0
9.0
6.0
5.5
3.0
7.5
10.5-
il.5
C.5-
11.5
4.5-5.5
1.5
7.5
3.0
6.5""
9.0
5.5
10.5
3.0
6.5
9.0
5.5
7.0
10.0
4.5
2.5
"On individual sources, odor ol».jerv:itions
less than 4 in frequency were dropped.
On composite chart, odor observations less
than 10 in frequency were dropped.
of intensity from various people in the
area subject to the odor, but one would
surmise that the description of the odor
would be uniform.
Most lay people attempting to de-
scribe an odor grope for words; they are
talking a foreign language. Odor memo-
ries are short and are susceptible to
outside influences. If one has been told
that there is an odor of dead fish from a
certain plant because of a failure, every
odor from that plant could smell like
dead fish to the untrained observer.
The Bureau of Smoke Inspection has
studied ways and means to get a better
description of the area subjected to
smells from various sources. During the
summer of 1953 an odor route was laid
out covering about 23 miles and passing
many known sources of odor pollution.
A procedure for reporting intensity as
well as description was designed.
One of the problems of the field in-
spectors was to see if a series of basic
descriptive terms of odor could be
applied to the situation with any degree
of uniformity between inspectors with-
out a course of instruction in odor
recognition.
For odor description, the chart shown
in Fig. 1 was employed. This came to
the Bureau's attention several years
ago while conferring with Dean Foster
who at that time was Head of the
Psychophysical Laboratory at Joseph E.
Seagram Co., Louisville, Ky. This chart
is reported to have all the descriptive
phrases necessary to describe, the com-
plete range of odors.
Figure 2 shows the route traveled and
Fig; 3 the information recorded. All
observation runs were made in the eve-
ning, starting after 6:00 p.m., and were
finished as late as midnight. This time
was chosen because the meteorology of
the area intensifies odor pollution during
these hours. Runs were made nightly
five days a week.
As malodor situations were observed,
35
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CRUDER ON ODOR POLLUTION
plants under the jurisdiction of the From this experience, the Bureau
Bureau of Smoke Inspection were con- believes that the odor chart needs
tacted to sec that the odor source was simplification and clarification to make
abated. The inspectors from the Bureau it more useful. This will be done before
reported about four occurrences for it is used during the summer of 1954.
Soop ond Detergent
Manufacturing
Mill Creek
Municipal Dump
Sewer Downstreom
from Chemicol
Manufacturing Plant
*
•5
Composite of oil Observations
FIG. 4.—Graphical Distribution According to Odor Chart (Fig. 1) of Odor Observations from
Various Sources on Odor Route.
every complaint received. However, the
main objective of this program was to
determine the workability of the odor
language. The results of 57 runs are
summarized in Table I. Figure 4 por-
trays the relative location on the odor
chart of the odor reports.
In summarizing the needs of the air
pollution control official in dealing with
outdoor odor pollution, it must be
borne in mind that the usual complaints
involve very small concentrations of
pollutants of a complex nature so that
evaluation by the usual methods of
36
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SYMPOSIUM ON ODOR
sampling and chemical analyses are
difficult and time consuming. Thus, the
"sniff" method by trained observers
looms as the practical means of deter-
simplified chart of odor descriptions
and an odor intensity instrument would
be of great value to every official who
has before him the monumental task of
mining and describing the odor level. A refreshing odor polluted air.
APPENDIX I
FIRST AREA SURVEY
1. Date of survey—July 11, 1950.
2. Total number of families contacted:
Twenty-nine with 28 questionnaires
being completed. (NOTE.—One of the resi-
dents stated that a member of the house-
hold was employed by the company and
did not wish to be a party to the survey.)
3. Length of residence:
The majority of the people contacted
lived in the vicinity a relatively short time.
Length of residence by groups:
Over 20 yr 1 ~• —•
10 to 20 yr 3
StolOyr 3
Under 5 yr...".. 21—with the average resi-
dence of the 21 being
2\ yr; the shortest
length of residence
was 2 months.
4. Description of odors complained of,
with the number of times the particular
category was mentioned by the com-
plainant:
Dead fish 13
Mothballs 11
Rotten eggs 9
Ammonia 7
Distillery 5
Shoe polish 5
Cooking paint or varnish 3
Chemical odor 2
Blue haze, choking 2
Chlorine 1
Glue factory 1
Broccoli 1
Gas 1
Polecat 1
Fresh cut hay 1
Blue haze, no odor 1
Cannot describe 2
5. The severity of the odor was described as
follows, with the number of times the
particular description was used:
Unpleasant 22
Very strong 17
Nauseating 11
Irritating to eyes 4
Irritating to nose 4
Irritating to throat 10
Causes headache ' 2
Choking 3
Disgusting 1
NOTE.—Two other categories were listed
in the survey:
Smell does not bother us.
Not noticeable after a while.
None of the parties contacted would agree
to these descriptions of the severity of
the odor.
6. Time:
An effort was made to determine the
time when the odors first became of such a
nature as to cause complaint. The informa-
tion received in answer to this question
was so variable that, it cannot be summar-
ized. The most common answer, however,
was given as "Since moving in."
7. History:
This category was listed in order to at-
tempt to evaluate any improvement or
37
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CiKUliKK ON OlXJR POLLUTION
retrogression, and tlie summary of replies
is as follows:
Always the same 2
Bad, then none at random intervals. ... 10
Bad during war years and just as bad
since : 10
Bad during war years but better since.. 4
Improvement in the past year over the
past 5 yr 7
Worse this year 1
8. Time of day:
An attempt was made to evaluate the
time of the day during which the reported
odors were most noticeable. There is no
specific information, the majority reporting
that they may be bad day or night. The
details are as follows:
Worse during day 8
Worse during night 4
May be bad day or night 16
9. Effect of weather:
An effort was made to determine the effect
of weather. Following are the replies:
None 6
Worse in hot, dry weather 3
Worse in hot, wet weather 10
Worse in cool weather 1
Worse in winter 1
Worse in foggy weather 12
It seems that hot, wet weather and foggy
weather have the greatest influence in the
opinion of the neighbors.
10. Evidence of property damage:
This item was included to determine
whether or not there was evidence of prop-
erty damage. Replies were as follows:
No
Yes
Not marked.
21
6
1
In general the residents in the vicinity
of the company reported "no property
damage," whereas those living directly
across from the plant to the north reported
property damage.
ll.^Any sickness which your doctor traced
directly to the fumes or odors in the
neighborhood?
No 26
Not indicated 2
38
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PAPER 3
MALODORS - A BASIS FOR REGULATION
by
W. C. L. HEMEON
HEMEON ASSOCIATES
(c) Copyright by Air Pollution Control Association (1971).
Reprinted by permission from the Journal of the Air Pollution
Control Association, 2± (12) , pg. 770 (1971).
39
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Malodors-A Basis for Regulations
Wesley C. L. Hemeon
Hemeon Associates
Pittsburgh, Pennsylvania
Of the four major categories of objectionable air pollution effects, the sensory
offenses are considered to be of dominant importance, and should receive much
higher priority in governmental policy than has been accorded to them. This
applies with particular force to the malodors. This deficiency may be partially
due to the pre-eminent emphasis on the search for health effects and partly to
the problems of measurement of malodors which is of prime importance in the
framing of odor control ordinances in objective terms. The author shows that
malodors can be measured at the source with quite satisfactory precision, contrary
to commonly-held opinion. Ambient air quality with respect to malodors likewise
can be evaluated by a quite simple technique and with nontechnical personnel.
A compatible system of an ambient air quality standard and allowable emission
rates from sources is demonstrated, and the essential elements of an odor control
regulation ore described.
It is possible to embrace all of the po-
tentially objectionable air pollution ef-
fects in only four categories:
1. Long-term modification of the earth's
climate or ecology, caused by C02,
fine particles, etc;
2. Hazards to human health: (a)
Acute (respiratory) caused by sulfur
dioxide or its oxidation products;
(6) Chronic (.systemic) caused by
lead, CO. asbestos, and various metal
compounds;
3. Injury to vegetation and animals,
and corrosion of materials, due to
sulfur compounds, fluoride
ozone, PAN";
4. Offenses to persons, due to malodors,
irritation of the eyes and respiratory
tract, visible particulate matter
(coarse and fine).
When we distinguish fact from specu-
lation as to the various objectionable
effects suggested, and when we con-
sider the frequency of occurrence and
the numbers of people affected in each
category, the overwhelming importance
of tin; sensory offenses embraced in the
fourth category becomes quite obvious.
The three sensory offenses arc those
due to (1) fine particles, which produce
visible haiv. (2) the coarse ones re-
sponsible for dustfall, and (3) malodors.
If we bend our terminology slightly we
can include low decibel noise in this
category, also.
Offenses Due to Malodors
There is no certain basis for decision
as to which of the sensory offenses are of
principal importance, but we feel that
malodor is a leading candidate for the
topmost position. Disagreeable odors
are ubiquitous; they plague millions of
people in all large communities, and
may be the principal foundation of
public opinion that is playing such an
important supporting role in the im-
plementation of public policy, even
though such policy is not directed
toward reduction of malodors.
People exposed to malodors instinc-
tively react with annoyance or with
anger, and usually express their resent-
ment in allegations of hazards to their
health. The fact that the health al-
legations are inaccurate does not lessen
the importance of the offense in any
degree.
The Problem of Odor Measurement and
Air Quality Criteria
One may well ask why government
has been generally laggard in an attack
on a category of pollutants of such over-
whelming importance to people.
The emphasis of present govern-
mental programs on the assumed health
aspects of air pollution is partially re-
sponsible for the denigration of malodors
41
Journal of the Air Pollution Control Association
-------
and the oilier sensory offenses. This is
ironic indeed if tlie malodorous environ-
ment is really the prime stimulant for
public support of governmental pro-
grams devoted to seeking out health
hazards.
Another reason may lie partially in
unjustified frustration over the sub-
jective nature of malodors, a. misunder-
standing of the limitations of odor mea-
surements, and of the precision that is
attainable using improved techniques.
The following description of malodor
measurement will provide, a foundation
for the recommendations presented
later.
Source Measurements
We cannot measure odor quality, but
it can be inferred that if people com-
plain, the odor is objectionable.
We can measure odor quantity, how-
ever, because of the fortunate circum-
stance that varying dilutions of odor-
bearing nir streams can be prepared and
presented to humans without injury to
them. This permits one to determine
the dilution ratio which represents the
threshold of sensory perception.
A sample of odor-contaminated air is
collected from a source in a large plastic
bag. and brought to an odor meter for
evaluation. A volume of 3 to 5 cubic
feet is required to provide an adequate
reservoir for the repetitive odor test
techniques we recommend. The large
ratio of bag volume to wall area prevents
the rapid decay of odor intensity by ab-
sorption and transformation which may
occur when the sample is, collected in
glass syringes and other small-volume
containers. With the large sample vol-
ume recommended, a delay of an hour or
more before its evaluation is permissible.
Concentration units—gas streams
. Odor concentration is expressed in
terms of cither dilution ratio (e.g., cubic
feet dilution air per cubic foot odor-
bearing gas) or "odor units/cu ft". The
terms are synonymous.
Total emission rate is the product of
odor concentration and total gas flow
rate. It is, expressed either as cu ft/min
(meaning total rate of dilution air re-
quired for dilution of the total odor to
the threshold of sensation) or -as odor.
units/min. These terms also are synon-
ymous.
Concentration units—area sources
The most common ground level
sources of malodors are area sources
such as lagoons, sumps, oil separators,
spilled liquids on floors or on the ground;
and elements of process equipment such
as open tanks.
These surface area sources, "venti-
lated" by adventitious air currents,
require different treatment for sampling
and for determination of emission rate.
The method is based on the fact that
emission of malodor is proportional to
the area of the exposed surface, liquid or
solid as the case may be. Determina-
tion of emission rate requires first a
measurement of unit area odor poten-
tial, i.e., odor units pCr square foot or
cfm/sq ft. When this is multiplied by
the total exposed area, the total emis-
sion rate in odor units per minute or cu
ft/min is obtained. (Special tech-
niques, required for the quantitative
sampling of area odor sources, are be-
yond the scope of this paper.)
Ambient Air Sampling and
Air Quality Standards
The ambient air quality standard we
propose is designed to protect people
from disagreeable exposure to malodors.
This standard simply specifies that
there shall be no perceptible malodor
in an ambient air sample collected in
accordance with approved procedures.
The instantaneous concentration of
malodors downwind from a single iso-
lated source may change rapidly over a
very wide range, and any measured
concentration of a contaminant there-
fore depends on the sampling time.
The average pollutant concentration is
the result of some dilution of the in-
stantaneous peak concentrations by the
unpolluted air that drifts by the receptor
in the intervals between peaks.
The appropriate sampling time to
describe the offensiveness of malodors
to people is not known. It is obviously
short in comparison with sampling time
periods that are significant for other
atmospheric pollutants. We consider
that a 1-min period represents a fair
compromise, and is manageable in the
calculations presented later.
The ambient air sampling technique
itself involves taking a liberal volume of
ambient air into a plastic bag during a
1-min sampling period and then trans-
porting it to another location for evalua-
tion. Such a sample can be taken by a
single individual cruising in a motor
vehicle. The sampling apparatus in-
cludes a battery-operated blower, a
plastic bag of 4 to 5 cu ft capacity, and
a timer for the 1-min sampling time
specification. The air sample volume of
1]/2 to 5 cu ft is sufficient to avoid sig-
nificant decay of odor intensity in the
V • a Jlr'ii
V» .-'• r.-^e..^.' *-•:>u>J|
Figure 1. Odor meter in operation for the
evaluation of odor intensity of gas sample
contained in poly-bag at right rear. Two of the
three visible face pieces projecting from dis-
tribution box are in use.
period of an hour or so, and this pre-
serves its viability, easily permitting its
transport to an odor-free headquarters
for yes or no evaluation.
The evaluation procedure at the head-
quarters site is equally simple. A small
panel of impartial persons is assembled
and each in turn is requested to smell
the contents of the bag, the yes or no
response being concealed from fellow
panelists.
A violation of the ambient air stan-
dard will have been defined in the recom-
mended ordinance according to the
percentage of the panel voting "per-
ceptible."
Source of Odor Measurement
The details of apparatus and proce-
dure advocated by this writer for deter-
mination of source odor concentrations
have been previously published.1 The
essential requirements for maximum
sensitivity and optimum precision of the
measurement are summarized in four
operating principles given in Table I.
Apparatus is illustrated in Figure 1.
It is important to realize that al-
though derived by reference to the sub-
jective reactions of human subjects,
the odor emission data thereby ob-
tained are completely objective since
they can be employed in calculations-
and for any engineering purposes, with-
out exception, just as though they were
Table I. Minimum operating requirements for determination of
odor concentrations at optimum precision.
1. The sampling system shall permit preparation and presentation of a series of test streams,
in a systematic sequence of varying dilution ratios with a minimum lapse of time between
them
2. The samples shall be presented to each subject at flow rates of not less than 10 cu ft/min
3. Threshold values shall be derived by graphic extrapolation employing three or more dilu-
tion values whose logarithms bear a linear relationship to the numerically expressed
sensations of the subjects. This is to avoid dependence on Yes-No votes data near the
threshold
4. Subjects shall be presented with a sufficient number of sample series for the development
of agreement on threshold odor intensity by at least two of a .panel of three subjects. For
illustrative data see Table II
These four specifications frequently require presentation of 20 or more separate sample seg-
ments and require a single sample to have a volume of not less than 3 to 5 cu ft. This volume
also avoids rapid decay of odor intensities, preserving a sample adequately for periods ot 1
hour or more.
December 1971 Volume 21, No. 12
42
-------
Table II. Typical odor evaluation record by
a panel of 3 subjects, illustrating the nature
and function of a preliminary evaluation.
In a second cycle following the exploratory
series the votes on odor intensity yield
satisfactory agreement on Oli value of 2000.
Subjects and their votes
G
Dilution
W
1.
20.000
10.000
8,000
5,000
5,000
2,000
970
600
300
100
. Exploratory
0
0
1
0
1
2
1
1
1
2
series
1
1
1
1
1
2
2
2
2
3
0
0
1
0
1
0
1
1
1
2
II. Second series
10,000
5,000
2,000
970
600
0
0
1
2
3
0
1
1
2
3
0
0
1
2
1
N.B. Subject R had ho experience in odor
evaluation prior to these tests.
concentrations of some chemically
identifiable .substance, expressed in parts
per million, or of a participate suspen-
sion in milligrams per cubic meter.
Individual Differences
It is commonly believed that there is
an extremely wide variation among
different individuals in sensitivity to the
same malodor. We find in fact that
the differences are small, and that a
small panel of observers with very little
training can be employed effectively,
and can produce consistent evaluations
of odor intensities.
Where there is a difference in sensitiv-
ity among members of an odor panel, we
recommend that the perceptions of the
most sensitive individual in the group be
used for the ultimate determination of
odor concentration. In this decision,
we have in mind the limited number of
persons employed in the panel, and the
conviction that a minority of the af-
fected population ought to be protected
against disagreeable malodors. Our
treatment of the panel voting data there-
fore is consistent with this principle.
Experience shows that in a panel of
three persons, agreement of at least two
of them, and often all three, can usually
be obtained when the techniques pre-
viously referred to are used. Those
test principles are summarized in Table
I; and some typical data from actual
field emission surveys displayed in Table
II, illustrate the importance of repeti-
tion to liberal volumes of sample in a
sequence of dilutions.
Chemical and instrumental measurements
From time to time it is suggested that
the techniques of odor measurement
would be simplified if correlations could
be established between odor percep-
tions and the concentration of some
chemical compound which could be
determined analytically. It has been
suggested also that automatic monitor-
ing instrumentation for malodors should
be developed.
These objectives are probably unat-
tainable. For one thing almost all the
important sources of malodors are a
variegated mixture of complex organic
substances whose proportions are con-
stantly changing. A time-consuming
chromatographic analysis may correctly
identify the odor constituents which
exist for only a few minutes, after which
the composition of the malodorous mix-
ture changes, perhaps never to resemble
the original sample.
The effects of odor are subjective ones,
and their measurement must therefore
rest finally on the subjective methods
outlined herein. This means that the
techniques of analytical chemistry or
automatic monitoring instrumentation
can not be applied to the purpose of
measurement if they omit human per-
ceptions from their operation. An oc-
casional exception like hydrogen sulfide
can be noted where the chemical iden-
tity is known, is definite and unchang-
ing; but this is the exception that proves
the rule and does not modify the practi-
cal wisdom of that rule.
Odor Control Regulations
The basic requirement:; for an effec-
tive, fair, and admini.-tratable regula-
tion are the following:
(a) An ambient air standard for
malodors which can be measured and
wind*-relates to the welfare of people;
(6) A standard that can be adminis-
tered objectively, employing simple
techniques;
(c) Odor emission standards that are
compatible with ambient air standards,
and the availability of measurement
methods for emission rates which permit
calculation of ground level concentra-
tions. •
(This facility permits an independent
calculation of ambient air concentra-
tions for comparison with those mea-
sured directly at ground level.)
We have shown how the first two
requirements can be met and it now
remains to show how emission standards
can be derived that are compatible with
the ambient air standard.
The rate of dilution by atmospheric
diffusion and calculation of downwind
concentration of odors employing con-
ventional diffusion models can be deter-
mined in the same manner as for a chem-
ically identifiable pollutant, and with
the same degree of confidence. (When1
di.-crepancies occur between observation
and calculated prediction, attention
should be directed to the validity of the
source measurement.)
Elevated Sources Versus
Level Ground Sources
IJecause of the dirTereuces in atmo-
spheric diffusion characteristics a dis-
tinction is necessary between elevated
malodor emissions as from exhaust
stacks, and those from ground level
sources. The elevation of the source
results in lower concentrations of mal-
odor at ground level due to greater dilu-
tion, during unstable atmospheric condi-
tions, and by isolation of the elevated
malodor stream from ground level
during the nonturbuient periods of in-
versions. Height is significant not
only to take account of the dilution po-
tential of the atmosphere downwind
but also to account for and avoid ob-
structions upwind that might cause
turbulent down wash.
Ground level source? lack these bene-
ficial circumstances. Dilution is greatly
reduced even when the air is turbulent,
compared with elevated sources; and
during atmospheric inversions at ground
level, very little dilution occurs and
people downwind are hardly protected
at all. Long distance is the only posi-
tive circumstance for any protection,
and the value of this circumstance is
greatly reduced during jicriods of in-
version.
For regulatory purposes we suggest
this definition of source height:
'•'Height of the malodor emission is de-
fined as the elevation aljovc the sur-
rounding terrain or building structures."
Emission Standard for Elevated Sources
For those odor sources which can be
channeled through a stack, we can for-
mulate a regulation that is based on a well
known dispersion model, i.e., maximum
ground level concentration, and also on
the knowledge that the objectionable
effects of point sources of malodors can
often be prevented by turbulent diffu-
sion, i.e., discharge into the atmosphere
from an elevated stack.
The maximum ground level concen-
tration, Cm.x, due to emissions from an
elevated source upwind, is given by
2Q '•
---- :-
unit'- elevated and
the concentration to be considered is at
ground level, we can consider the ratio
to be essentially unitx for our purposes.
43
Journal of the Air Pollution Control Association
-------
ifuhr-tilutinj: the numerical values for e
:uid pi (2.7IS and 3.14) the equation
reduces to
.-.9. c*>
4.UJW/I5 W
The equation states the simple fact
that concentration is the rate of emis-
sion divided by rate of ventilation pro-
vided by the natural diluting capacity of
the atmosphere.
In the case of chemically identifiable
gases the value nf Q would have a defi-
nite value ami C,,.,v would be expressed
in conventional units. In the case of
odors, however, the rate of emission, Q,
is expressed in volumetric air flow units,
i.e.. rate of dilution required to reduce
the odor to the threshold of sensory
perception. It is expressed here in the
units: cubic feet per minute (synony-
mous with odor units per minute). It
describes the required rate of dilution as
may be provided by the turbulent diffus-
ing capacity of the atmosphere between
the point of emission and the ground
level locations where maximum con-
centration occurs.
Thus, in these terms, the equation
states that
Kate of odor emission
Table III. Example regulation, elevated
sources. Allowable odor emissions where
the point of discharge is greater than 100 ft
above the surrounding teirain and building
structures.
Kate of dilution by atmos.
diffusion
ft'/min fre>h air to dilute to
_ ____ threshold ___
ftymin dilution available, by
atmos. cliff.
Now, if we specify that the rates shall
be unity, i.e., numerator equal to de-
nominator, we have an equation all
of whose terms are measurable:
i't3/min to dilute to threshold
'
The Kate of Odor Emission in the
numerator is the product of the dilution
ratio. K (the volume of air in cubic feet,
required to dilute 1 cu ft of the odor
bearing gas stream to threshold), found
by odor meter and the total flow of
contaminated air, G (ft'/min). The
Mai rate of odor emission is GR.
Low wind velocity is unfavorable to
effective dilution, assuming the air
stream is nonlmoyant. and it is there-
fore wise to base the calculation of per-
miss.ible odor emissions on some low
though realistic wind speed. We sug-
gest -100 ft/inin (i.e., 4.5 miles/hr).
The equation win now be simplified to
1= __ ___
(4.16) (400)/i*
Height above
terrain or nearby
obstructions, ft
100
150
200
250
300
350
400
500
Etc.
Allowable odor
discharge rate.
odor units
per minute
(cu ft/min),
million
1.7
3.8
6.7
10
15
20
27
42
Etc.
or
Gff=1670/i! (Ihr) (5)
December 1971 Volume 21, No. 12
One final adjustment is required
before the expression is ready for appli-
cation to regulations. The concentra-
tions calculated by the Cmnx formula are
those that would correspond to a sam-
pling time of one hour, approximately;
and since we have recommended a
sampling time of one minute for the
ambient air standard, we must establish
compatibility between that ambient
standard and the emission standard.
A simple ratio describes the difference"
between the longer and the shorter
sampling time and reflects the varying
degree of dilution due to waves of clean
uncontaminated air drifting past the
receptor between the peaks of contami-
nated air. The ratios of concentrations
during the one minute averaging time to
a GO minute averaging time are different
according to the type of atmospheric
turbulence. Those ratios are 14, 8, and
4 in "very unstable," "unstable," and
"neutral" atmospheres, respectively.2''
For maximum protection of poten-
tially affected persons in the neighbor-
hood, and taking account of other real-
ities, it is suggested that the maximum
concentration of odors (1 min) should
not exceed one-tenth of the hourly
concentration. When this ratio is ap-
plied to the expression above, we obtain
GR = 167A2 (1 min) (6)
An example regulation in tabular
form based on this equation is shown in
Table III for elevated sources.
Sources lower than 100 ft are arbi-
trarily defined in the example, as ground
level sources. Regulations describing
maximum odor emission rates for ground
level sources can be derived by the same
procedure displayed above, substituting
an equation appropriate to ground level
sources.
Example-Odor Control Regulation
The essential provisions of an odor
regulation incorporating these concepts
a re as follows:
1. An ambient air quality standard
which is designed to protect the. rights
of neighbors can be quite simply and
44
briefly stated: "A one-minute aver-
age sample of air collected and evalu-
ated according to approved proce-
dures, in places where people reside,
shall be free of perceptible odors."
2. Emission standards should be com-
patible with the ambient air stan-
dard (Table III).
(This rule provides an objective en-
gineering basis for measurements at a
source and derivation of independent
conclusions about ambient air con-
centrations.)
3. A showing of compliance with emis-
sion standards should be recognized
as a valid defense against allegations
based on ambient air samples.
4. In the evaluation of ambient air
quality, these four procedural details
are important: (o) sample volume at
least 1% cu ft; (6) sample should span
a period of one minute: (c) the col-
lected sample should be transferred
to a site isolated from the odor source;
(d) a positive-or-negative evaluation
by a panel of four or more impartial
persons should be obtained; (e) posi-
tive votes by two of the panel shall
determine the conclusion.
5. For evaluation of odor concentrations
at a source, the operating princi-
ples shown in Table I should be ob-
served.
Conclusion
The type of ordinance recommended
provides an administrative authority
with ambient air sampling techniques to
establish objective proof of an odor of-
fense. It can then point to and accuse
an upwind source. Any accused source,
conversely, can defend itself if innocent,
by source measurements showing com-
pliance with odor emission standards.
References
1. Hemeon, Wesley C. L., "Technique and
apparatus for quantitative measure-
ment of odor emissions," J. Air Poll.
Control Assoc., 18 (3), 166 (March
1968).
2. Singer, Irving A., "The relationship be-
tween peak and mean concentrations,"
Air Poll. Control Assoc., 11 (7), 336
(July 1961).
3. ASME Committee on Air Pollution
Controls; Smith, Maynard, Ed. "Rec-
ommended Guide for the Prediction of
the Dispersion of Airborne Effluents,"
Chapt. IV, 1st Ed., Amer. Soc.
Engrs., May 1968.
Mr. Hemeon is Director of
Hemeon Associates, 6025 Broad
Street Mall, Pittsburgh, Pa. 15206.
This paper was presented as Paper
No. 71-21 nt the 6-lth Annual Meet-
ing of the Air Pollution Control
Association at Atlantic City.
-------
PAPER
DEVELOPING ODOR CONTROL
REGULATIONS: GUIDELINES AND
CONSIDERATIONS
by
W. C. PROKOP
APCA TT-4 ODOR COMMITTEE
(c) Copyrighted by Air Pollution Control Association (1978)
Reprinted with permission from the Journal of the Air
Pollution Control Association, 28 (1), pg. 9 (1978).
45
-------
DEVELOPING ODOR CONTROL REGULATIONS:
GUIDELINES AND CONSIDERATIONS
William H. Prokop
Vice Chairman, APCA TT-4 Odor Committee
The TT-4 Committee developed a position paper on
odor control regulations. Present odor regulatory ap-
proaches are considered generally to be unsatisfactory.
There are two basic needs: 1. develop sound adminis-
trative procedures for establishing the existence of a
community odor nuisance, and 2. obtain reliable odor
sensory data that can be related to community accep-
tance or annoyance of a particular odor. Specific issues
regarding administrative procedures for odor regula-
tions are presented. These include establishing the va-
lidity of odor complaints and the existence of a com-
munity odor nuisance, based upon a specified number
of valid complaints being received within a fixed time
period. The existence of a community odor nuisance
should be established before a compliance program is
applied to an odor source. Technological needs for odor
regulations are discussed. These include the develop-
ment and testing of improved odor sensory measure-
ment techniques, critical evaluation of atmospheric
dispersion models to predict ambient odor concentra-
tion and relating ambient odors to annoyance thresh-
olds for different communities or zoned areas. A sug-
gested approach to odor control regulations is detailed.
Specific procedures are provided for validating com-
plaints, for establishing the existence of a community
odor nuisance, for locating the alleged source(s) causing
the odor problem and applying a compliance program
to the source.
The TT-4 Committee of APCA is primarily concerned with
bnsic odor technology: its measurement, control, and regula-
tion. Many of its members have contributed technical articles
on odor regulations in recent yenrs.1 4
At the APCA Annual Meeting held in June 1974, a Critical
Review of Regulations for the Control of Odors was conducted
in cooperation with the TT-4 Committee. As a result of the
discussions of this critical review, the Committee decided it
would be helpful to develop a position paper on odor control
regulations that would provide guidelines to agencies desiring
to adopt such regulations.
Initially, voluntary comments were solicited from the
Committee members regarding two basic questions:
1. With the present state of the art in odor sensory mea-
surement and other technology including' odor control,
what specific type of odor regulations would be the most
feasible?
2. If the desired odor sensory measurement and other
technology is available, what specific type of odor regu-
lation would be the most feasible?
For both questions, the respondent was asked to cite specific
examples of odor sensory measurement and other technology
to support the choice of odor regulations. Many diverse
comments were received and a variety of issues was raised.
These comments were incorporated into a first draft of the
position paper which was circulated among the Committee
members for additional comment. A later draft resulted from
these comments. Two special meetings of the Committee were
held in early 1977 to review the later draft and possibly to
reach a consensus on specific issues.
The total input toward the position paper was provided by
comments recieved from 17 out of a total Committee of 26
members. This represents about two-thirds of the Committee
and hopefully provides a reasonable consensus. Of the 17
member participants, two are from regulatory agencies, five
are from academic or research oriented institutions, and ten
are from industry. This distribution of participants is directly
proportional to the actual makeup of the total Committee.
Due to the diverse comments received from the Committee
members, it is difficult to portray an accurate consensus for
the various controversial and relevant issues that influence
the development, and promulgation of specific odor control
regulations. The author is well aware of the problem in at-
, tempting to achieve a proper balance between the pros and
cons presented by others regarding such issues. As a result,
this position paper is considered to be a "perceived consensus"
of the Committee.
As an example, the Committee was about o<|imlly divided
on the basic issue of selecting stack emission type standards
as opposed to ambient odor type standards. Moth approaches
have strengths and weaknesses. The stack omission approach
Copyright 1978— Air Pollution Control Awociition
January 1978 Volume 28, No. 1
47
-------
ODOR CONTROL REGULATIONS
has obvious advantages over an ambient odor type regulation
regarding the relative ease and lower cost of sampling and
analyzing odors. Also, the emission source of objectionable
odors is more readily determined by using stack measure-
ments. However, the stack emission type approach requires
an additional technical step—the correlation of stack emission
with ambient odor concentration, either by obtaining em-
pirical data or by use of atmospheric dispersion models, in
order to be able to judge whether or not the resulting ambient
odor concentration is acceptable to the community.
On the other hand, if odor annoyance threshold data are
available, an ambient odor limit can be related to a particular
zoned area and specified to avoid an odor annoyance being
experienced by the population that lives or works in a par-
ticular zoned area. Further, it should be recognized that odors
do not discharge only from stacks or well defined enclosures
but could originate from fugitive type emissions (i.e. anaerobic
lagoons). As a result, it may be necessary in certain areas to
have a combination of stack emission and ambient odor reg-
ulations available to control all significant sources of odor.
Baste Issues
The issues discussed in this paper are separated into those
which are related to regulatory administrative procedures and
those which have an essentially technical basis. For example,
establishing the existence of a nuisance should usually follow
a specific regulatory procedure whereas the choice of a method
for measuring an odor emission from a stack involves a tech-
nical decision. It is the consensus of the Committee that the
desired approach for odor regulation involves the use of rea-
sonable administrative procedures for confirming the exis-
tence of an odor nuisance and the availability of an established
technical base for measuring odor concentration and deter-
mining odor annoyance.
Objectives
Primary objectives of this position paper on odor control
regulations:
1. Determine effectiveness of agency enforcement of current
odor regulations.
2. Review and evaluate current administrative procedures
for odor regulations.
3. Determine odor measurement and control technology
needs for odor regulations.
4. Develop a suggested approach to odor control regula-
tions. .
5. Determine specific technical gaps to be plugged.
At the APCA Specialty Conference: State of the Art of Odor
Control Technology 11 held in Pittsburgh during March 1977,
Jim Franz of the TT-4 Committee presented a paper on the
subject, of standardizing odor terminology. The odor terms
defined at the Pittsburgh Conference are incorporated into
this position paper.
Agency Enforcement of Current Odor Control Regulations
A number of agencies specify either the use of the ScentO''
meter' for measuring the odor concentration in the ambient
air or the ASTM syringe dilution technique for measuring the
odor concentration or odor dilution ratio of a stack type
emission. The basic static syringe method is described by
ASTM11 and has been modified by others7'8 to eliminate the
trial and error feature of the original method.
Six state agencies and the District of Columbia specify the
use of the Scentometer for ambient odor measurement. It
nppeitrs that most of these regulations were enacted without
the agencies having the benefit of field experience with the
Scentometer. Specific problems were discussed" regarding its
application to ambient air measurement. A major difiit. ••':..
concerns its use by an individual who is surrounded by the
odorous environment that is to be measured. Since the nose
is easily desensitized under these conditions, it is most difficult
accurately to detect differences jn odor concentration in the
ambient air.
Three state agencies designate the use of the ASTM syringe
method with sensory panel procedures specified by either
Mills7 or Benforado8 for establishing whether or not compli-
ance is achieved with a stack type odor limit. Although
Friedrich9 reported reliable results with the ASTM syringe
method, it was emphasized that training of the odor sensory
panel is particularly important and following consistent
procedures is essential. Further, monitoring of the odor panel
results is critical to establish the reliability of each panelist's
response.
The basic ASTM method lacks a defined procedure for odor
stimulus presentation since the various odor dilutions are to
be presented randomly to the panel by mixing the order of
strong and weak odor stimuli. Sometimes, a blank or odor-free
sample is substituted to check the panel's reaction which tends
to produce confusing results. As a result, no satisfactory pro-
vision is available to check the reliability of positive-negative
responses of the panel other than through experience.
In an attempt to overcome this one basic shortcoming of the
ASTM method, the syringe dilution technique has been
modified10 to provide for an ascending order of odor concen-
tration in presenting the odor stimuli to the panel, and at each
dilution level two syringes are submitted to each panelist. One
syringe contains the odor stimulus and the other is a blank
containing odor-free air. However, the amount of data ob-
tained using this technique is limited.
Discussions with various regulatory agencies that currently
specify or use the ASTM syringe method for monitoring stack
emissions indicates a desire to have available improved odor
sensory methods. In fact, one agency contracted with a re-
search firm to conduct a comparison study1' which evaluated
three dynamic olfactometer methods and the ASTM syringe
method. The study concluded "the ASTM syringe static
dilution technique should not_be used if a dynamic dilution
method is available." Presently, only one agency in the U.S.
specifies the use of a dynamic olfactometer method in odor
control regulations.12
There has been a definite reluctance expressed by some
state and local agencies considering new regulations to in-
corporate the use of the ASTM syringe.method or Scento-
meter. Instead, they prefer to retain the nuisance concept to
regulate odors. Further, those agencies which do specify either
of these two odor measurement methods still have an odor
nuisance regulation or various criteria for determining an odor
to be objectionable. However, the agencies recognize the
limitations of the odor nuisance concept and Feldstein2 in-
dicated "the enforcement of such n statute (nuisance) is at liest
difficult."
It must be concluded that present odor regulatory ap-
proaches are generally unsatisfactory. There are two basic
needs: (1) develop sound administrative procedures for con-
firming the existence of a community <>dor nuisance, and (2)
obtain reliable odor sensory data that can be related to com-
munity acceptance or annoyance of a particular odor.
Administrative Procedures for Odor Regulations
Regulatory administrative procedures are the essence of any
odor regulation.. The procedure is inherently related to what
is the intent or objective of the regulation, for example, to
resolve and eliminate valid complaints. However, technical
issues can be strongly influenced by the choice of procedure
presented in the regulation. For example, if the odor regula-
tion states that no odor is to be detected beyond the property
line of any source, this degree of odor control may not be
achievable either technically or economically.
48
Journal of the Air Pollution Control Association
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Administrative procedures should take into consideration
the interests and concerns of the public, the source(s) and the
agency. The public usually reacts to objectionable odors by
registering complaints with either the agency or source. An
effective regulatory procedure provides the mechanism for
resolving odor complaints in a fair and timely manner (in-
formally, if possible) with reasonable administrative effort and
without judicial intervention unless required.
The TT-4 Committee in its various comments on odor
regulations raised specific issues regarding administrative
procedures. An attempt is made below to clarify these issues
and bring them into sharper focus:
1. Odor control regulations usually are concerned with ob-
jectionable type odors which are not harmful to health.
Hazardous or toxic odorous vapors and gases require a
separate type of regulation. In this case, measurement and
control of a specific chemical compound is required to
maintain its concentration in the ambient air below an
established physiological danger level.
The Federal EPA considered the application of per-
formance standards for new stationary sources to ren-
dering plant odors. However, its analysis established these
odors to be a noncriteria pollutant affecting only public
welfare but not health. As a result, the Federal EPA has
left the regulation of odors to the state and local agencies.
The Committee agreed that odor problems are basically
related to the local community and should be regulated
by the appropriate local agency.
2. Classification of odors and odor sources could be useful
in developing meaningful odor regulations. It should be
clear what specific types of odors and/or sources are to be
excluded from the regulations.
In certain instances, an odor source may be intimately
connected with the socioeconomic use of an area. For
example, certain state agencies111 recognize the necessity
of agricultural operations and these are specifically ex-
empted from odor regulations. Likewise, agencies ac-
knowledge that certain materials must be odorized for
safety purposes (i.e. mercaptan in natural gas) and these
are exempted from regulation.
3. Chemical identification and measurement by continuous
instrumentation for the monitoring and control of a single
odorant or similar groups of odorants is a more convenient
approach to controlling odors than odor sensory testing.
For example, one agency1- currently has specified total
reduced sulfur (TKS) limits for the kraft pulp mill in-
dustry. However, it may be desirable to correlate odor
sensory data with the concentration of chemical constit-
uents for certain applications, particularly if a judgment
is to be made regarding these emissions being the cause
of odor complaints.
4. Odor complaints are indicators that a potential odor
problem may exist in the community. It is essential that
a regulatory agency has established procedures for re-
ceiving and investigating odor complaints. These proce-
dures should clearly establish whether or not a complaint
is valid. The use of a printed form to record the complaint
received and the findings of the agency inspector would
be desirable.
5. There should be specific procedures and guidelines pro-
vided to establish the existence of a community odor
nuisance which take into account the community's
characteristics: population distribution, socioeconomic
activity, and land use zoning. The use of validated odor
complaints to establish the existence of a community odor
nuisance provides n measure of the basic odor prob-
lem - the annoyance expressed by the community and not
merely the detection of odors. Copley International
Corporal ion" in their Phase 111 study for the KPA, con-
cluded that "technological controls on I lie annoyance
threshold rather than the odor threshold... would^ pro-
mote more efficient solutions ...."
Certain agencies15 employ a procedure where an ob-
jectionable odor is defined to exist "upon (the) decision
resulting from investigation by the department based
upon the nature, intensity, frequency, and duration of the
odor ...." Subjective judgments by the agency inspector
should be avoided. There is a definite need to develop
objective criteria that can be quantified regarding the
quality, intensity, frequency and duration of an odor that
relate directly to the annoyance experienced by the
community.
6. The TT-4 Committee arrived at an essentially unanimous
consensus that the existence of a community odor nui-
sance should be established first before regulatory limits
are applied to a specific odor source to obtain compliance.
The procedure for establishing a community odor nui-
sance would require a specific number of valid complaints
being received from separate households during a fixed
time period. One agency12 requires the receipt of odor
. complaints from ten or more people within a 90 day period
before specific odor limits are applied to an alleged source
of objectionable odors.
7. As a concept of odor regulation, the issue was raised
whether or not stack emission or ambient odor standards
should be set with the intention that odors not be detected
beyond the property line of the source. This type of
standard confuses the perception of an odor with the ex-
istence of a problem. The Committee unamimously
agreed that this approach is unreasonable and places an
undue restraint upon a particular source where the best
available technology may not be capable of achieving this
ultimate degree of control.
8. As an administrative procedure in regulating odors, the
Committee was essentially unanimous in their comment
that a regulatory agency should consider the investment
and operating costs of odor control techniques in applying
a compliance program to an odor source. This approach
requires knowledge ol the incremental cost lor a specified
odor removal or reduction in complaints. For a significant
increment of odor control investment, there should result
a demonstrated reduction in the community »dnr prub-
Icm instead of merely reducing the odor level of emis-
sion.
9. An effective odor regulation specifies the criteria to be
complied with but not the method of odor control re-
quired to achieve compliance. The choice of a control
method should be up to the individual source but with
agency approval, because this choice usually is dependent
upon a combination of economic and technical factors
directly related to the source.
Incineration standards have been promulgated"' for
rendering plants and for fifteen other industrial catego-
ries. This is an example of a type of regulation that
n|xvifit's a control method. Unfortunately, the application
January 1978 Volume 28. No. 1
49
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of this type of regulation often ignores the availability of
other proven technology. In the case of incineration, the
unavailability of natural gas and rising fuel costs are key
issues affecting the choice of this method for odor con-
trol.
OsJormln® Technology Woods for Odor Regulations
The choice of technology for monitoring and evaluating
odor emissions regarding their annoyance or acceptance by
the community is no less important than the administrative
procedures which are selected to implement a specific odor
control regulation. The Scentometer and ASTM syringe
methods currently used by state and local agencies are con-
sidered by the Committee to be inadequate for regulatory
purposes. There is a basic need for odor sensory methods
which are capable of measuring odors objectively and reliably.
Unless such methods are available, odor regulatory problems
will continue to be resolved by a court's interpretation as to
the existence of an odor nuisance being based on evaluating
the subjective testimony of opposite parties.
Our Committee considered two categories of technical
issues: (1) the current technology available for application to
odor regulations, and (2) the new technology needed to pro-
vide for more effective odor regulations. These technical issues
are discussed below:
1. Based on odor technology currently available for mea-
surement and control, limiting the odor dilution ratio
of the stack emission is preferred as a method of cor-
recting an odor problem. However, applying rigid limits
to stack emissions should be avoided. Flexibility should
be provided with some allowance being made to take into
account local conditions and type of zoning. Monitoring
the stack emission to reduce the odor intensity to a level
that avoids a nuisance problem together with a reason-
able compliance schedule would accomplish more than
the blind application of rigid single-number type lim-
its.
2. One state agency17 currently has in effect a limit on total
odor emission rate of one million odor units per minute.
This limit is obtained by multiplying the volumetric
emission rate in cubic feet per minute by the odor dilu-
tion ratio measured at the emission source and expressed
in odor units per cubic foot. This limit can also be ex-
pressed in terms of metric volumetric units. It is inter-
esting to note that this state agency relies basically upon
the stack emission limits, expressed in odor units per
cubic foot, for enforcement of their odor regulations.
The Committee was equally divided regarding their
approval of or opposition to a total odor emission rate
being applied for regulatory purposes. Those in favor
considered this concept to be useful since another di-
mension other than odor concentration is available for
evaluating an odor nuisance. In particular, it provides
the means for totalixing a multiple number of odor
emissions from a single source.
Those opposed to this concept recognize it has a cer-
tain validity when applied to small volume emissions.
However, they question this concept when applied to
large volume emissions, for example, from plant venti-
lating air scrubbers. Kased on the previously cited total
odor emission limit of one million odor units per minute,
a lOO.OOO cl'm scrubber would be allowed a stack emis-
sion odor concentration of only 10 odor units. This
clearly is unrealistic and it is doubtful whether the.
specified syringe dilution technique is sufficiently sen-
sitive at this low odor level to establish compliance reli-
ably. The basic objective for an odor regulation should
be to limit the ambient odor concentration at grou"!
level, Cmax, rather than the total odor emission rate, Q,
where both terms relate to atmospheric dispersion
models.
It appears that the concept of total odor emission rate
could be useful as a guideline for evaluating an odor
nuisance but it should be applied judiciously for regu-
latory purposes.
3. Odor sensory measurement for stack emissions currently
include both the static ASTM syringe method (Mills
modification) and a number of different dynamic ol-
factometers. There is a consensus of the Committee in
favor of the dynamic olfactometer and phasing out of the
ASTM syringe method for regulatory enforcement. The
dynamic olfactometer methods, compared to the static
ASTM syringe method, can provide results which are
obtained more quickly, with better reproducibility, with
training of the odor panel being a less critical factor, with
more consistent procedures in presenting the odor
stimuli to panel members, and results which are related
to statistically significant confidence levels.
It has been experimentally proven1" that a significant
difference in odor sensory value exists when detecting
the same odor stimulus with the ASTM syringe method
as compared to dynamic sensory methods and poten-
tially large variations can exist between different dy-
namic methods. For example, when comparing various
dynamic olfactometers with the ASTM syringe method
at a level of 100 odor units (ASTM), two dynamic
methods experienced an estimated threefold increase
in odor unit values whereas a third dynamic method
produced an estimated twentyfold increase. As a result,
odor sensory data should always be identified with the
particular odor sensory met bod that is used.
Basic criteria should be established for dynamic ol-
factometers that are used for odor control regulations.
Adequate technical documentation is necessary to es-
tablish the sensitivity and reliability of the dynamic
method as well as to describe it accurately in order that
others can check and compare results.
4. Ideally, it is desired to determine stack emission odor
concentrations that result in ambient odor concentra-
tions which would be acceptable to the community or a
particular zoned area. To establish this, it would be
necessary to determine the odor annoyance threshold
for the average population of the community. Unfortu-
nately, very little data are currently available on odor
annoyance thresholds. If available, an ambient odor
concentration below the average annoyance threshold
would be chosen to represent an acceptable level and this
would be related to the desired stack emission odor
concentration. Atmospheric dispersion models must be
relied upon to relate the stack to the ambient odors for
different meteorological conditions.
5. There was definite controversy among the Committee
members regarding the degree of precision that can be
achieved with atmospheric dispersion models in pre-
dicting ambient odor concentrations from stack emis-
sions. Those members attesting to their validity indi-
cated that the dispersion models can be used with con-
fidence in making such predictions. Those members
questioning the validity of dispersion models were con-
cerned with the lack of scientific data in the technical
literature that would validate the calculated ambient
odor concentrations with empirically determined values.
The odor sensory methods used for source emission and
ambient odor measurement should be compatible in
order that data comparisons can be made.
• There are considerable experimental data relating
predicted and observed values for single odorunt type
emissions. However, limited data are only available on
50
Journal 08 th® Air Pollution Control Association
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"odors" (mixtures of various odorants or chemical
compounds.) Lindvall19 reported the use of Hogstrom's
method20 for estimating atmospheric dispersions when
the odor thresholds were determined for emissions from
a sulfnte pulp mill by the sampling and sensory methods
described by Lindvall. Excellent agreement was obtained
between observed and predicted odor detection
frequencies for a distance up to 2 km from the source, but
the predicted values for 5 and 10 km corresponded to a
half and a third of the observed values, respectively.
There is a basic need to collect and publish available
odor sensory data comparing observed and predicted
values of ambient odor concentration in order to rein-
force the use of atmospheric dispersion models.
6. Measurement techniques are needed to evaluate the
odorous emissions from fugitive sources (i.e. anaerobic
lagoons) where odors escape directly from the source into
the atmosphere. Hemeon21 proposes the use of a pool
simulator that would test a sample of wastewater by
directing a measured volumetric flow of air across a fixed
area of water surface within the simulator and measuring
the resultant odor concentration of air discharging from
the simulator. These data would be applied to a specific
pool of water whose surface area is known and the total
odor emission rate would be calculated in odor units per
minute.
Based on the use of an atmospheric dispersion model,
the ambient odor concentration could be calculated and
compared with empirically determined values. This
approach is analogous to that discussed in item 5 re-
garding stack emissions.
7. Measurement of ambient odors has been performed with
the Scentometer and also with dynamic olfactometers.
There is a consensus of the Committee that the Scen-
tometer is not a satisfactory instrument for measuring
ambient odors, primarily because the individual is sur-
rounded by an odorous environment.
There is a definite need for measuring ambient odors,
not only for comparison with predicted values obtained
by atmospheric dispersion models, but also to determine
the ambient odor concentration and be able to relate it
directly to an annoyance experienced by the community.
More test work is required to validate the use of dynamic
olfactometers for this purpose. The same basic criteria
should be established for dynamic olfactometers used
for measuring ambient odors as for stack emissions (refer
to item U).
8. Obtaining representative samples of ambient air for odor
sensory measurement is recognized as a basic problem.
Additional test work should be conducted to improve the
understanding of these parameters of ambient air sam-
pling. These include the duration and frequency of
sampling and use of odor locating techniques.
9. Tin- relating of ambient odors to annoyance thresholds
for different communities or /oned areas is fundamental
to establishing ambient odor type standards. This could
be accomplished by determining dose-response rela-
tionships that equate annoyance with odor intensity and
the degree of unpleasant character of a particular odor.
For example, dose-response relationships have been
investigated by Kendall'2- for diesel exhaust odors and
by Lindvall111 for odors associated with kraft pulp mills.
A specific mathematical relationship could be developed
by population testing to equate odor intensity with an-
noyance threshold expressed in terms of percent of
population response. The selection of the actual ambient
odor limit would be based on this mathematical rela-
tionship and should bo set nt a reasonable level below the
mean or .r>()% population response that would be ac-
ceptable to (he community and yet be economically
achievable. The selection of this ambient odor limit
should normally follow a specified statistical proce-
dure.
This is a relatively complex approach to developing
odor regulations. However, there is a strong consensus
of the Committee that it could prove to be useful as a
long term approach. As a result, it would be necessary
for the funding of this program to be provided by the
Federal EPA as opposed to any state or local agency.
10. The technical capabilities of various odor control tech-
niques should be established relative to their ability to
reduce odor intensity to specific levels. These odor re-
ductions should be directly related to investment costs
and operating expenses to establish a cost effective re-
lationship. The application of specific odor control
techniques could vary for different categories of indus-
trial sources depending upon the odor intensity, chem-
ical constituents present, and volumetric emission
rate.
Suggested Approach to Odor Control Regulations
Effective odor regulations are needed. What is meant by
"effective" in this context? It could mean achieving a specific
but relevant goal that is responsive to the public without
causing undue hardship to the odor source and yet is reason-
able for the agency to administer. The TT-4 Committee
considers this goal to be the elimination of or at least reduction
of valid odor complaints to a level below that specified to be
a community odor nuisance.
The Committee is primarily concerned with the adminis-
trative procedures and technical features which could be in-
corporated into odor regulations for achieving the desired goal.
If the existence of a community odor nuisance is confirmed,
voluntary compliance by the odor source is encouraged. If the
source refuses to comply, legal procedures should be available
for the agency to obtain compliance. The Committee consid-
ered the specifying of such procedures to be outside the scope
of this paper.
A suggested approach to odor control regulations is outlined
below:
1. Validation of odor complaints by specific procedures that
provide for receiving and investigating each complaint.
2. An administrative procedure for establishing a commu-
nity odor nuisance. This procedure would specify the
number of valid complaints received from separate
households during a fixed time period.
3. Positively locating the alleged source(s) causing the
community odor nuisance. Monitoring the odor emissions
from the source(s) with odor sensory methods to provide
a basis for estimating the degree of odor reduction re-
quired to correct the community odor nuisance.
4. Applying a specific compliance program to the source(s)
in order to correct the community odor nuisance. Pro-
viding a target odor emission concentration for the source
to be in position to select and obtain the necessary odor
control equipment.
A more detailed discussion of this suggested approach is
presented below.
Validation of Odor Complaints
The following procedures are suggested for receiving and
investigating odor complaints:
1. Each complaint received by phone would be logged on a
printed form to identify the name and address of the
complainant. Also logged on the complaint form are the
time and location of odor exposure, the length of exposure
time, the intensity of odor exposure (strong, moderate or
weak), a description of the odor, the wind direction and
identification of the alleged nource if one is perceived.
January 1978 Volume 26, No. 1
51
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ODOR CONTROL REGULATIONS
If the complainant desires not to be identified to the
source, confidentiality could be provided. However, if
legal proceedings are necessary, it is possible the com-
plainant may be asked to testify.
2. The alleged source (if known) would be contacted without
delay and informed of the complaint including the exact
time and location of exposure. This permits the alleged
source an immediate opportunity to respond to the
complaint. Also, a voluntary resolution of the odor com-
plaint could be achieved. The agency should avoid accu-
mulating a number of complaints before notifying the
alleged source.
3. Coincident with item 2, an agency inspector would be
dispatched without delay to the scene of the complaint
to establish its validity. The presence of odor, its intensity
and duration, the wind directions, interview with com-
plainant, investigation of potential sources, identification
of and interview with alleged source(s) are measures to
be considered in establishing the validity of the com-
plaint.
A printed form for investigating odor complaints would
be filled out by the inspector for each complaint. A per-
manent record of these findings could be kept and made
available to the alleged source and public, except for the
name of the complainant if confidentiality is desired.
4. The alleged source, if identified, could be contacted by
the inspector and requested (but is not required) to re-
spond in writing to the complaint. The alleged source
should indicate its position and action to be taken re-
garding the complaint. This written response likewise
could be kept as a permanent record by the agency and
made available to the public.
5. Voluntary complaints should be received by the agency
before they solicit complaints from others.
Establishing a Community Odor Nuisance
An administrative procedure in the regulation would be
provided to establish the existence of a community odor
nuisance. Ths procedure would specify the number of valid
complaints received from separate households during a fixed
time period.
The TT-4 Committee suggests that a community odor
nuisance exists when a significant number of people from
separate households allege the existence of an objectionable
odor and an investigation of these complaints by the agency
confirms this. The specification of what exactly is "significant"
is dependent upon the community's characteristics such rs
population distribution, socioeconomic activity, and land use
zoning.
The existence of a community odor nuisance should be es-
tablished first before regulatory limits are applied to a specific
odor source to obtain compliance.
Locating the Alleged Source(«)
The investigative procedure for determining the validity
of euch complaint should provide information which may
identify or locate the source(s) causing the community odor
nuisance. However, actual testing of the odor emission from
thi- source(s) may provide a more objective basis, not only for
locating the (tourer of the problem hut also the proportionate
contribution of each source if multiple sources are involved.
As a result, it is essential that the technical capability be
available for sampling and measuring odor emissions from the
source with reliable odor sensory methods.
For stack type emission, the following procedure is sug-
gested:
1. An acceptable odor sensory sampling and measurement
method is described and documented in detail for use by
both the regulatory agency and the individual sources.
2. The alleged source(s) are tested by sampling the stack
emissions to determine the odor dilution ratio by the ac-
cepted method. Also, the volumetric flow rate from the
stack(s) is measured. If multiple sources are involved, the
percent contribution toward the odor nuisance can be
estimated from the odor sensory data obtained.
This testing could be omitted when a single source is
only involved and the solution to the odor problem is self
evident.
3. Monitoring the stack emission for odor dilution ratio
provides a basis for estimating the degree of odor reduc-
tion required to correct the community odor nuisance.
As was indicated previously, an odor sensory measuring
technique is also available for evaluating the odor emissions
from fugitive sources.
It should be recognized that considerable test work is still
required to validate the use of odor sensory methods consid-
ered to be suitable for regulatory purposes to measure the odor
emissions from stack and fugitive type sources.
Compliance Program
In applying a compliance program to a source, a stack type
emission is chosen as an example to illustrate this suggested
approach.
When a specific source is identified as contributing to the
community odor nuisance, an informal meeting could be held
between the agency and the odor source. The purpose of such
a meeting would be to collect and exchange information for
establishing a compliance program to eliminate or at least
reduce valid complaints below the number specified to be a
community odor nuisance.
The elements of such a compliance program are suggested
below and it is assumed that new odor control equipment is
required:
1. Odor sensory testing of the stack emission(s) from the
source to determine the odor dilution ratio and volumetric
flow rate for each emission that potentially could cause
the odor problem. The odor sensory method used should
be acceptable to the agency.
2. Establishing a target odor dilution ratio for the stack
emission(s) at a specified volumetric (low rate. This is a
key step in the compliance program and is necessary for
estimating the degree of odor reduction to be achieved
with the new control equipment.
This target value should not be set unreasonably low
to ensure that no odor be detected beyond the property
line of the source because this approach may not be
technically and/or economically achievable. Instead, the
primary incentive for establishing the target value is to
eliminate or reduce valid complaints below the number
specified to be a community odor nuisance.
There was definite controversy among t he Committee
members as to how this target value should be arrived nt,
based upon currently available odor sensory dala. This
disagreement is characteri'/ed by the discussion in the
previous section (Technology Needs item f>) regarding
the use of atmospheric dispersion models for predicting
52
Journal of the Air Pollution Control Association
-------
ambient odor concentrations from stack emissions.
An atmospheric dispersion model can be a useful tool
for estimating a stack odor concentration that results in
an ambient odor concentration which would be acceptable
to the community. However, it also is important to de-
termine the odor annoyance threshold that can be related
to the population of the community experiencing the odor
problem. Based on this knowledge, an ambient odor
concentration can be selected below the known annoyance
threshold which would be reasonable and yet capable of
avoiding complaints. The availability of odor annoyance
threshold data is rather limited and more odor sensory
data are required to compare observed and predicted
values of ambient odor concentration resulting from at-
mospheric dispersion models.
An estimate of the target stack odor concentration
could be made with an atmospheric dispersion model
based upon a selection of an ambient odor concentration
to avoid complaints. Various meteorological conditions
should be considered to take into consideration the local
factors. These include the present odor concentration and
volumetric rate of the stack emission, the location of the
odor complaints with respect to the odor source, the
prevailing wind direction and speed, atmospheric sta-
bility, the surrounding topography, duration of averaging
exposure time, and frequency of occurrence during the
year. The selection of values for these meteorological pa-
rameters should be reasonable for achieving compliance
but yet are capable of preventing exposure to a commu-
nity odor nuisance.
The stack odor concentration estimated from the at-
mospheric dispersion model should be reviewed carefully
and as is appropriate, adjusted based upon the best
available technical information regarding odor control
technology and the cost required to achieve the desired
odor reduction. The ability of the source to finance the
new equipment investment and associated operating costs
should also be a consideration.
3. Based upon the target odor dilution ratio which is estab-
lished for the stack emission, the source with agency ap-
proval would select a specific method of odor control. As
a result, the source would investigate the availability of
odor control equipment and the delivery time required.
It is possible that pilot plant or commercial scale testing
is required to confirm performance before new equipment
is ordered. The compliance schedule should allow suffi-
cient time for the various phases of the project to be
completed.
The overall solution to the odor problem should not be
limited to only a choice of odor control method but also
should allow for selecting a stack height to utilize the
dispersion capability of the atmosphere.
4. A final meeting between the agency and the source should
result in a compliance program that consists of a written
agreement stating specific items to be accomplished
within a definite time period.
5. When the necessary equipment has been installed and put
into operation, the system would be tested and the stack
odor dilution ratio determined. The frequency of valid
odor complaints would be noted. If significant valid
complaints are being received during a certain time pe-
riod, monitoring the stack emission of the new control
system is important to establish whether this source or
another is causing the odor problem.
After an adequate time has been allowed to establish
a history of odor complaints subsequent to the startup of
the new odor control system, the agency and the odor
source would have an informal hearing. Its purpose would
ba to arrive at a conclusion regarding the correction of the
community odor nuisance, determine if further action is
required and establish a stack emission odor monitoring
program that is contingent upon the number of com-
plaints received.
The results of this meeting should be confirmed in
writing. Such a written document would not preclude a
community odor nuisance being established in the future
for this particular source, provided that the specified
number of valid complaints are received during the fined
time period.
Technical Gaps to be Plugged
In the section under Technological Needs, a number of
items are listed for which experimental work may be required.
First, all available information and data on each specific issue
should be collected and evaluated. Then, wherever specific
technical gaps are determined to exist, test programs should
be developed and executed.
1. Basic criteria should be established for dynamic olfacto-
meters that are to be used for measuring stack emissions
and ambient odors (refer to items 3 and 7) for regulatory
purposes. Jim Reinke of the TT-4 Committee has ini-
tiated a test program for a round-robin evaluation of dy-
namic olfactometers.
2. The use of atmospheric dispersion models to predict
ambient odor concentration from stack and fugitive type
emissions should be critically evaluated (refer to items 5
and 6). Reliable odor sensory data are needed to compare
observed and predicted values of ambient odor concen-
tration. Such available data should characterize results
obtained for single odorant compounds and compare
them with those obtained with "odors" (mixtures of
various odorants or chemical compounds). Bob Kenson
of the TT-4 Committee is collecting information and data
regarding atmospheric dispersion models in order that
the Committee is in position to develop guidelines for
their use and recommend further test work.
3. Techniques in sampling ambient odors should be inves-
tigated (refer to item 8).
4. Relating ambient odors to annoyance thresholds for dif-
ferent communities or zoned areas is fundamental to es-
tablishing ambient odor type standards (refer to item 9).
However, this represents a relatively complex technical
program since considerable testing would be required and
specific industrial sources would have to be considered
for such a program. Federal funding would be required
to accomplish this.
In connection with relating odors to annoyance, it
would be desirable to quantify the terms: quality, inten-
sity, frequency, and duration of an odor to establish ob-
jective criteria for determining an odor to be objection-
able.
5. Establish the technical capabilities of various odor control
techniques for different industrial categories to reduce
odor intensity to specific levels. For each odor control
technique and industrial category, determine a cost ef-
fective relationship between the odor reduction achieved
and the investment costs and operating costs expend-
ed.
Summary
Present odor regulatory approaches are considered gener-
ally to be unsatisfactory. There are two basic needs: (1) de-
velop sound administrative procedures for establishing the
existence of a community odor nuisance, and < l! > i-btain reli-
January 1978 Volum® 28, No. 1
53
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ODOR CONTROL REGULATIONS
able odor sensory data that can be related to community ac-
ceptance or annoyance of a particular odor.
Specific issues regarding administrative procedures are
presented. These include validating odor complaints and es-
tablishing that a community odor nuisance exists before
applying a compliance program to the odor source. Likewise,
technological needs are discussed. These include improved
sampling and odor sensory measurement techniques for stack
emissions and ambient odors, critical evaluation of atmo-
spheric dispersion models to predict ambient odor concen-
trations, and relating ambient odors to annoyance thresholds
for different communities or zoned areas.
A suggested approach to odor control regulations is detailed.
Specific procedures are provided for validating complaints,
for establishing the existence of a community odor nuisance,
for locating the alleged source(s) causing the odor problem,
and applying a compliance program to the source.
It is the hope of the TT-4 Committee that this position
paper will stimulate interest and discussion on the part of all
segments of the community; the public, industrial sources, and
the regulatory agencies. In particular, the Committee desires
that the technical members of the community participate
actively in the development and testing of improved odor
sensory methods that will provide the needed scientific data
for effective odor control regulation.
Acknowledgment
The author is sincerely grateful to the members of the TT-4
Committee for their significant, individual efforts and con-
tributions to this position paper. An attempt was made to
consider the diverse comments received and provide a balance
that hopefully approximates a consensus of the Committee.
If any Committee member feels this was not achieved, the
author so apologizes.
References
1. W. C. I,. Hemeon, "Malodors—a basis for regulations,"!/. Air Poll.
Control Assoc. 21: 770 (1971).
2. M. Feldstein, D. A. Levaggi and R. Thuiller, "Odor Regulation
by Emission Limitation at the Stack," paper 73-273 presented
at APCA Annual Meeting. June 1973.
3. W. H. Prokop, "Status of Regulations for Source Emission and
Ambient Odors," paper 28 presented at The New York Academy
of Sciences, Conference on Odors: Evaluation, Utilization and
Control. Oct 1973.
4. G. Leonardos, "A critical review of regulations for the control of
odors," J. Air Poll. Control Assoc. 24:456 (1974).
5. N. A. Huey, L. C. Broering, G. A. Jutze, and L. W. Gruber, "Ob-
jective odor pollution control investigations," J. Air Poll. Control
Assoc. 10:441 (1960).
6. Standard Method for Measurement of Odor in Atmospheres
(Dilution Method) ASTM-D1391-57 (reapproved 1967), 1972
Annual Book of ASTM Standards Part 23, American Society
Testing Materials, Philadelphia, PA.
7. J. L. Mills, R. T. Walsh, K. D. Luedtke, and L. K. Smith,
"Quantitative odor measurement," 13: 467 (1963).
8. D. M. Benforado, W. J. Rotella, and D. L. Horton, "Development
of an odor panel for evaluation of odor control equipment," J. Air
Poll. Control As.ioc. 19: 101 (196!)).
9. H. E. Friedrich and D. M. Benforado, "Utilization of the Odor
Panel Technique for Evaluating Odorous Industrial Emissions,"
paper 73-271 presented at APCA Annual Meeting, June 1973.
10. ASTM D-22 (Sensory Evaluation Committee) Task Force D
22-02.09, "Proposed Revision of D 1391-57 Standard Method for
Measurement of Odor in Atmospheres (Dilution Method)," April
1977.
11. The Research Corporation of New England, "Technical Report
to the Illinois Environmental Protection Agency on the Evalua-
tion of Four Odor Measurement Systems," Dec. 1975.
12. Bay Area Air Pollution'Control District, San Francisco, California,
Amendment to Regulation No. 2, Division 15, "Odorous Sub-
stances," Effective May 5,1976.
13. State of California Health and Safety Code, Section 41705: De-
scription of Agricultural Operations Exempted.
14. Copley International Corporation, "A Study of the Social and
Economic Impact of Odors—Phase III," Final Report prepared
for the Environmental Protection Agency, Feb. 1973.
15. State of Wisconsin Air Pollution Control Rules, Chapter NR154,
Section 154.18, Effective April 1, 1972.
16. State of Pennsylvania Standards for Contaminants, Chapter 123,
Section 123.31, Adopted Sept. 2, 1971.
17. State of Minnesota Pollution Control Agency Regulations APC-9
and APC-10, Effective Sept. 14, 1971.
18. J. P. Wahl, R. A. Duffee and W. A. Marrone "Evaluation of Odor
Measurement Techniques: Volume I Animal Rendering Indus-
try," report prepared for U. S. Environmental Protection Agency
(EPA-650/2-74-008-a) Jan. 1974.
19. T. Lindvall, "On sensory evaluation of odorous air pollutant in-
tensities," Nord. Hygiene Tidxkr, Supplement 2 (1970).
20. U. Hogstrom, "A method for predicting odor frequencies from
a point source," Atmos. Knuiron. 6: 103 (1972).
21. W. C. L. Hemeon, "Measurement of Fugitive Odor Sources,"
APCA Specialty Conference on Odor Control Technology II,
Pittsburgh, PA, March 1977.
22. D. A. Kendall, P. L. Levins and 0. Leonardos, "Diesel Exhaust
Odor Analysis by Sensory Techniques," paper 740215 Automotive
Engineering Congress, Feb. 1974.
Critique
J. Nell Mulvaney
Ontario Ministry of the Environment
Although it does not achieve all that it sets out to do, the
Committee Paper is a stimulating and useful contribution.
One of the primary objectives of the Position Paper is stated
to be the determination of the effectiveness of agency en-
forciTm-nt of current odor regulations. This objective does not
appear to have been achieved. The paper concludes that,
"present odor regulatory approaches are generally unsatis-
factory," but no real evidence is offered in support of this even
by reference. The regulatory agencies are chidcd for preferring
to retain the nuisance concept to regulate odors, either as the
54
Journal of the Air Pollution Control Association
-------
sole tool or as backup where odor measurement techniques
are specified. A reading of the paper seems to confirm the
wisdom of such agencies, at least until the technical gaps
identified in the paper have been plugged.
A crucial assumption made in the paper is that hazardous
or toxic odorous vapors and gases require a separate type of
regulation. Because the ability to do this is essential to the
acceptability of the kind of regulation proposed in the paper,
some statement should have been made about the feasibility
of categorizing and separating out odors which are hazardous
or toxic and those which are not. The distinction is also im-
portant because once it has been made, it might allow a reg-
ulatory agency with limited resources to allocate them more
meaningfully.
The concept of "a community odor nuisance" occupies a
fundamental place in the Committee Paper. Before entirely
buying the idea that the existence of such a community odor
nuisance should be established before regulatory limits are
applied, I would want to have some assurance that alternative
arrangements were available so as not to leave unprotected,
members of the public who do not happen to be located in a
populous area. The concept of the community odor nuisance
is likely designed to eliminate the need to satisfy those
members of a community who may be abnormally sensitive.
It should be mentioned that this objective tends also to be
achieved in respect of the nuisance standard or similar criteria.
It will usually be necessary to have testimony from several
affected members of the community before success in this
kind of litigation can be confidently predicted. Notwith-
standing the above comments, the writer feels that the concept
of "a community odor nuisance" is an important one.
The paper indicates that the establishment of the existence
of a community odor nuisance should take into account the
characteristics of the particular community. This does not
seem to be unreasonable if a fair way can be worked out to
accomplish it. A similar approach has been taken to noise
control by-laws, although it should be pointed out that in that
area more data are available as to annoyance and discomfort
thresholds.
The pnper indicates that the Committee was essentially
unamimous in commenting that a regulatory agency should
consider the investment and operating costs of odor control
techniques in applying a compliance program to an odor
source. This is a very broad statement and I am not sure of its
exact meaning. If if suggests that the onus on this issue will
always be on the regulatory agency, then I do not agree with
the thinking. In my view this would be inconsistent with the
other firm conclusion reached that "the choice of a control
method should be up to the individual source but with agency
approval." It seems to me that once the community odor
nuisance has been established, it is up to the source to come
forward with a realistic program acceptable to the agency to
eliminate the nuisance. It will only be where such a program
is not forthcoming that the agency is forced to direct the im-
plementation of a program. When the agency is forced into
that position as a result of the failure of the source to come
forward with a program, it seems to me that the onus should
be on the source to bring forward data on investment and
operating costs and to demonstrate that for a specific incre-
ment of odor control investment there will not be a significant
reduction in the community odor problem. Also, if the Com-
mittee is suggesting here that if there is no technique suffi-
ciently effective to solve the problem that is economical for
n particular company, then compliance should not be required,
then the writer disagrees. The courts, in nuisance cases, have
held that an operation which cannot be carried on within the
law, cannot be carried on at all. Surely, our environmental
legislation should not permit lower standards of protection
than those which have been imposed by the courts for centu-
ries.
The determination as to the existence of an odor nuisance
made by a court is said to be based on an evaluation of the
subjective testimony of opposite parties. The thrust of the
paper here places confidence on technology not yet fully tested
in favor of a standard applied by the courts for a long time. So
long as the courts consider the evidence of each witness
carefully, and reject evidence of those witnesses who appear
to be biased or influenced by some improper motive, abuses
are not likely to happen. Also, evidence in such cases is not
entirely subjective. If a witness has gotten up in the night to
close his bedroom windows or if the children are forced out of
their own backyard into the house by objectionable odors,
these events in themselves may be demonstrated as factual.
Perhaps some discussion would have been helpful in the
report on the issue of side effects which can result from a so-
lution to an odor problem. One of the illustrations of this is
where, in order to correct an odor problem, noisy control
equipment has been installed which, in turn, results in com-
plaints from the community. It may be that this raises an issue
which could be usefully dealt with in the guidelines.
The paper infers that the enforcement of a nuisance statute
is difficult and also implies that such provisions in the law are
undesirable because they are too subjective. 1 have already
dealt with the issue of subjectivity. Our own experience in the
Province of Ontario shows that enforcement is not that dif-
ficult and indicates that the courts are quite comfortable with
the traditional nuisance standards which they have worked
out over hundreds of years. The concept of an emission which
causes material discomfort to some person is not all that dif-
ficult for the ordinary person to understand and, indeed, may
be more relevant to him than numerical standards. For this
reason, it may be that it would be wise to preserve the provi-
sions of this kind in the law, at least in the foreseeable fu-
ture.
The only real reference to legal procedures in the report is
a statement to the effect that they should be available for the
agency to obtain compliance and that they are outside the
scope of the paper. It is suggested that the issues raised by
legal considerations are not that easily put outside the scope
of the paper, the purpose of which is to develop guidelines and
considerations for developing odor control regulations. As was
pointed out above in respect of the nuisance kind of standard,
we are dealing with principles which have been established
for a long time in the law and these questions must be ad-
dressed if any consideration is given to removing them by
substituting alternative approaches. Considerations of this
kind are inherent in the development of u regulation as are
considerations of civil rights, access to information, and
questions of appeal. For example, the method of determining
whether a community odor nuisance exists is set out rather
generally in the paper and in the actual development of a
regulation of this kind you would probably have to come to
grips with the question of how a determination made by the
agency can be challenged through some appeal or review
process.
Notwithstanding the above observations, I wish to re-
emphasize that the Committee Paper is an extremely stimu-
lating and important contribution.
55
January 1978 Volume 28, No. 1
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Minnesota Pollution Control Agancy
Regulatory agencies with jurisdiction in the pollution con-
trol area would tend to agree with the position of the TT-4
Committee of the Air Pollution Control Association that
present methods of regulating the emission of odorous pol-
lutants have been cumbersome and unsatisfactory. One of the
reasons for this, as the TT-4 Committee points out, is the lack
of adequate monitoring equipment, but another major reason
is the fact that state and federal regulatory agencies have
placed their major emphasis on the so-called criteria pollu-
tants—particulate matter, sulfur dioxide, nitrogen oxides,
photochemical oxidants, carbon monoxide, and hydrocar-
bons.* However, since a large percentage of complaints about
air pollution received by regulatory agencies involves odor
pollution, there will continue to be a growing interest in the
regulation of industries which emit odorous pollutants and
new regulatory approaches will undoubtedly be forthcom-
ing.
The TT-4 Committee in its position paper has discussed
several major aspects of odor regulation which I identify as
(1) the objective of odor control, (2) the regulatory standard,
and (3) administration of the standard. I would like to critique
the position paper under those major headings.
Yh® Qbjecilv® of Odor ControD
The TT-4 Committee identified the objective of odor reg-
ulation as the abatement of odors in the ambient air to a level
below an average annoyance threshold level that is based on
a community odor nuisance standard.00 The TT-4 Committee
also suggests that the objective is to abate a community odor
nuisance after it has been established.
I think'regulatory agencies would have two major areas of
disagreement with the TT-4 Committee position. One, the
objective of odor regulation must be to prevent the odor from
occurring in the first place, not to abate it after citizens have
complained. Two, the objective is to eliminate the odor for all
noses in the community, including the sensitive ones. Rei
duction of the odorous pollutant only to a level that does not
annoy the average nose is unacceptable. I recognize that often
such activities as farming may not be regulated at all and that
such considerations as zoning and population may influence
the necessity or intent to regulate odors. However, once a
regulatory agency acting within its authority determines that
regulation of odorous pollutants is appropriate, the objective
must be to prevent the existence of an odor in the ambient air
for all citizens in the community.
It should be pointed out briefly that the objective of odor
regulation as far as the regulatory agency is concerned depends
to a-great extent on the intent of the legislative body which
created the agency. The regulatory agency can only carry out
the duties and functions which the legislature has authorized
it to carry out.
* These are specific pollutant* identified by the U.S. Knvironmenul Protection Agency on
pollutant* which hnve An adverse effort on public health or welfare. See Clean Air Act $108,
4'J I' S.C. ls\K,- c-:i «nd 40 C.K.R. Pnrt SO (1976).
** An interest ing analogy that romrs to mind in the United Suteo Supreme Court'o holding
that stnlrs may apply "contemporary community standards" an part of the tent in deter-
mining whether certain material in obscene. Sep Millm*. California. 413 U.S. 15(1973). See
also I'ari, Adult Theatre 1 V. Slatiin. 413 U.S. 49 (1973) and Smith u. United State*. 45
I I.S.I.. W. 44!).ri (1977). I am reminded of the words of Mr. Justice Stewart in Jaeobellia u.
Ohio. :17KII.S IK4(l%4t where he snid: •
I shall nut ludny attempt further to define the hinds of material I underoUind to b? era*
hrmed within the nhorlhnnd description (hard-core pornography); and perhaps I could
never oucceed in intelligibly doing »o. Hut 1 bnow it when I neo it....
The question here is what should the law (i.e., the regula-
tion) provide so that the objective is maintained. This is the
step at which the regulatory agency establishes the numbers
or criteria which the emitter of the odorous pollutants must
achieve. Adoption of the standard by regulatory agencies has
nothing to do with enforcement, or the validity of complaints,
or the identity of emission sources, or the development of
compliance programs. Complaints, for example, may lead to
the development of a standard, but individual enforcement
activities do not occur when the standard is being devel-
oped.
We should focus here, then, only on the criteria that should
be contained in an odor regulation. The TT-4 Committee
discussed the merits and demerits of an ambient standard and
a stack emission standard. Regulatory agencies generally use
both standards and the TT-4 Committee recognizes that both
are needed. The ambient standard is necessary because this
is the underlying objective, and the stack emission standard
is necessary because it is the best mechanism for assuring that
the ambient standard is achieved. This is the approach used
by the regulatory agencies and envisioned by the Clean Air Act
for meeting the ambient standards for the criteria pollutants.
For example, an emission standard which limits the amount
of sulfur dioxide which may be emitted by a power plant is
developed that is adequate to meet the ambient standard for
S02. A similar approach is appropriate in the odor control
area.
The TT-4 Committee recommends an ambient standard
in terms of the number of valid complaints received from
separate households during a certain period of time. The
regulatory agencies, as the Committee recognizes, rely basi-
cally on a nuisance standard.* The different standards result
because of the underlying differences between the Committee
and the agencies over the extent of odorous pollutants which
should be permitted in the ambient air.
The TT-4 Committee discusses the lack of adequate reliable
odor sensory devices for measuring odors. There can be no
doubt that reliable equipment would provide a tremendous
assistance. Such equipment would be a valuable compliance
tool to determine the extent of odors in the community.
Moreover, it would substantiate modeling techniques used
to determine stack emission standards necessary to meet
ambient standards.
Stack emission standards are a necessary element of an
adequate odor regulation. The TT-4 Committee prefers a
stack standard that is a target odor dilution ratio determined
* Nuisance law may vary slightly from state to state but Minnrsola'M definition of nuisance
b illustrative of the others. Minnesota Statutes, Sect ion Mil.nl i I'.l7t>) defines nuisance in
the following terms:
Anything which in injurious to health, or indecent or offensive to the senses, or an ob-
otrurtion to the free use of property, DO an to interfere with the comfortable enjoyment
of life or profierty, io a nuisance.
56
Journal of «ha Air Pollution Control Association
-------
after an odor problem occurs. This is chronologically and
perhaps legally inappropriate. The stack emission standard
must be included when the regulation is promulgated, oth-
erwise a new source would be permitted to be constructed and
to create an odor problem where one did not exist before.
Furthermore, it provides an identical stack standard for all
existing sources, rather than an ad hoc one, which the Com-
mittee seems to prefer.
One aspect of emission standards that the TT-4 Committee
discusses only briefly is the approach of establishing emission
standards for specific odor-causing pollutants. The example
the Committee mentions is total reduced sulfur limits for the
kraft pulp mill industry. The most effective method to avoid
odors in the ambient air is to limit the amount of odor-causing
pollutants which may be emitted. While this approach re-
quires more effort to isolate the odor-causing pollutants which
may be emitted. While this approach requires more effort to
isolate the odor-causing pollutants, to determine their odor
thresholds, and to relate their ambient thresholds to a stack
concentration, it is my judgment that in the future there will
be more regulations setting these kinds of standards.
A factor which the Committee fails to consider is the
"technology-forcing" aspects of pollution control. "Tech-
nology-forcing" is a phrase which the courts have developed
to describe a philosophy that pollution control is so important
that claims of economic or technical infeasibility can not ex-
cuse noncompliance. See Union Electric v. Environmental
Protection Agency, 96 S. Ct. 2518 (1976) and Train v. Natural
Resources Defense Council, 421 U.S. 60, 90 (1975).' There
may be instances in which industry will be required to develop
the technology necessary to alleviate an odor problem.
In sum, it appears that the TT-4 Committee and the regu-
latory agencies agree that changes will be forthcoming in odor
regulation. Developments in odor sensory devices will expedite
these changes. Future regulations will continue to require
compliance with both ambient and emission standards, and
in my judgment these standards will be more specific and
more stringent than is suggested by the Committee.
Administration of the Standard
Once the standard is adopted, of course, it remains for the
regulatory agency to administer it and to insure that all ex-
isting and new sources comply with the requirements of the
regulation, regardless of whether the standard is a community
nuisance standard, an emission limitation, or some other
' These cases involve interpretations of the federal Clean Air Act. The "technology.furcing"
requirement wan derived from a reveiw of the legislative history behind the Act. Senator
Muskie. explained the hill to the SenMe in the following words:
"The first responsibility of Congress is not the making of technological or economic
judgment —or even to IM- limited by what is or appears to he technologically or economically
feasible. Our responsibility is to establish what the public interest requires to protect the
health of iMTsons. This may mean that people und industries will l>e asked to do what seems
to be impossible ut the present time." 1 lf> Cong. Kec. :tt!X>l -yfXI'2 (1970).
standard. Much of this administration will involve validating
complaints, identifying sources, and resolving compliance
schedules, as the Committee suggests. I have no quarrel with
this portion of the paper, as most of my disagreement involves
the requirements of the standard itself, but there are several
points I wish to make regarding administration or enforce-
ment of the odor regulation.
Once a standard is duly promulgated all sources that fall
under the purview of the regulation are required to comply
with it. Compliance at this juncture means nothing less than
meeting the numbers and criteria of the regulation. If the
standard does not require a certain number of complaints, as
I promote, then compliance is required whether complaints
are received or not. Sources will be required to install the
necessary pollution control equipment regardless of the
number of complaints.
The Committee has expressed a concern that a source have
an opportunity to present data to the regulatory agency re-
garding the economics of compliance. Depending on the laws
of the jurisdiction in which the source is located, an individual
source may apply for a variance from the standard on the
grounds of economic hardship. In addition, the source most
likely had an opportunity to present general economic data
to the agency at the time the regulation was adopted.
One factor which does not seem to be given adequate weight
by the Committee in discussing administration of the regu-
lation is the length of time needed by the source to meet the
standard. New sources must comply upon commencement of
operation but existing sources will require a period of time to
install pollution control equipment to meet the standard.
Informal dispositions are preferred by the regulatory agencies
and the sources, but if operation is to continue in violation of
the standard while equipment is being installed, the compli-
ance schedule must be kept to a minimum. In developing these
compliance schedules, the number of complaints will certainly
be a factor.
Conclusion
I have two major disagreements with the position of the
TT-4 Committee. One, a community odor nuisance standard
which requires a certain number of complaints over a certain
period of time is inadequate. The standard must be designed
to eliminate the odor for all the citizens. Two, an odor problem
cannot be allowed to develop before abatement efforts need
be undertaken. Pollution control equipment must be installed
before the problem occurs.
Regulatory agencies are in accord with many of the posi-
tions taken by the Committee. Certainly development of re-
liable odor sensory devices will be a tremendous asset to both
the agency and the source in identifying and preventing am-
bient odor problems. In addition, the equitable administration
of whatever odor standard is promulgated is in the best in-
terests of the agency, the source, and the public.
Comments
Morton Sterling
Wayne County Department of Health
This is a written summary of comments made at the TT-4
Committee presentation of "Position Paper on Odor Control
Regulations".
We take major exception to any guideline document that
establishes or attempts to determine the validity of citizen
January 1978 Volume 28, No. 1
57
odor complaints based upon the number registered per unit
time. This is a matter which each community must establish
for its own basis of action. Of course, in the ultimate a problem
may require a judicial decision. Local agencies have been
dealing for years with odor-type community problems and
-------
ODOR CONTROL REGULATIONS
they are quite adept at distinguishing between valid citizen
concerns and those of a harrassing or nonobjective nature.
The guidelines provide overemphasis in many areas on
zoning as an element in determining the validity of citizen
odor complaints and/or the seriousness of the problem, zoning
should not enter into a determination of the validity of citizen
complaints. Why citizens who reside immediately adjacent
to industrial activities should be treated as second-class citi-
zens is not understood. References to the zoning parameters
should be eliminated from the guideline document.
The report indicates that the ASTM syringe method is in-
adequate. It further indicates that a more objective and reli-
able means must be developed. Later wording suggests that
the ASTM syringe method is of no real value, when our office
has not found that to be the case at all. In fact, a recent civil
suit filed by this agency (which is now at the Appeals Court
level) received the wholehearted support of the Circuit Court'
judge in the application of the ASTM syringe method as the
cornerstone of our allegations. It is my understanding that at
the Tuesday TT-4 Committee meeting, the "round robin"
testing of the dynamic olfactory method of measurement
developed serious reliability problems of its own accord. Until
such time as another method is developed and recognized as
better than the ASTM syringe method, it certainly should be
considered acceptable for use in assisting with the evaluation
of odor problems and their solution, and some statement to
that effect should be made in the guideline document. Oth-
erwise, enforcement agencies will be left with no reasonably
scientific method to assess odor extent objectively, even
though it is recognized that better methods may come about
in the future.
The Committee report suggests that setting of an odor
standard with no odor is unreasonable and places an undue
restraint on the owner of the facility in question. This as-
sessment should be deleted from the report. The determina-
tion of acceptable community odor levels is a legislative pre-
rogative, and it could be that certain communities in their
wisdom would not wish that any odors be perceptible beyond
the boundary line of the source originating such emissions. It
is quite likely that most communities would not adopt such
a posture, but certainly to call such a posture unreasonable
is unwarranted.
It is suggested that in the development of any agreement
with an odor emission source, such agreement be in writing.
We agree with this principle; however, we would suggest that
such agreement be in a legally enforceable format; that is, if
there is failure to honor the agreement that is written, such
features can be immediately enforceable in a court of law. Our
agency has developed such contractual relationships with
many offending sources, including owners of facilities which
generate odorous emissions creating problems to the com-
munity.
Before publication of the guidelines, it seems the Com-
mittee should earnestly solicit input from the Control Officials
Conference Committee of the APCA as well as STAPPA and
ALAPCO, the latter organizations being composed principally
of state and local air pollution control officials. It is noted that
24 of the 26 members of the TT-4 Committee are represen-
tatives of either industry directly or indirectly affected by the
guidelines or academic and consulting organizations, and only
two are from regulatory agencies. Input from a wider spectrum
of control officials would be helpful in providing a balance to
the report.
Comments
A. Turk
City College of the City University of New York
Mr. Prokop is to be complimented for his fearless undertak-
ing of a complex and controversial task. I would like to offer
comments on three matters with which the paper is con-
cerned.
The measurement of odor by a dilution technique requires
some definition of the target concentration to be reached.
Abundant experimental evidence as well as theoretical con-
siderations based on signal detection theory provide con-
vincing arguments against the use of the detection threshold
as a target. The recognition threshold is not quite so bad but
is still not satisfactory. A much better target would be a
standard concentration of a standard odorant that provides
a mild but definite odor, such as, for example, 100 ppm of
n-butanol.
The problem of identifying a "valid" odor complaint is a
sensitive one, but in adversary situations, needs to be defined
operationnlly. I suggest that attempts to develop a criterion
bo addressed to the question of an "invalid" complaint, all
others then being considered to be valid. It is of course, widely
accepted that a complaint about a non-operating source, or
from an upwind location is invalid. There are many instances,
however, in which such straightforward evidence is not at
hand. It is therefore important to establish procedures, per-
haps based on odor recognition tests under controlled condi-
tions, to define a response which is demonstrably invalid.
Everyone agrees on the need for refinement of atmospheric
dispersion models for odors, especially with regard to the
appropriate time-averaging interval for establishing
ground-level odorant concentrations. It is important to rec-
ognize that the establishment of such a model is not simply
a paper exercise, but requires a carefully controlled, and rather
elaborate experimental design, possibly using a tower from
which odorant and a gas tracer are released simultaneously,
together with downwind sensory odor judgments and sam-
pling and analysis of the tracer over different time inter-
vals.
58
Journal of the Air Pollution Control Association
-------
Comments
J. C. Wykowskl
EXXON Research and Engineering Company
Regarding the TT-4 Odor Committee paper on Odor Regu-
lation, we believe that the basic goal of a regulation should be
to prevent ambient odors that are a nuisance to the commu-
nity and that control methods to reach these goals should not
be specified by regulatory bodies. In enforcing odor regula-
tions, the cost effectiveness of alternate solutions should be
considered. For example, we consider a limit on the total odor
emission to be a penalty on large installations which is not cost
effective.
Tools to predict whether there will be an odor problem from
a plant are needed in order to design plants to prevent odor
complaints. This is preferable to waiting for odor complaints.
After causing a nuisance, it is always more difficult to achieve
reasonable solutions especially with regard to the time needed
for implementation. We agree that technical areas worth
pursuing in this regard are:
• Establishing annoyance thresholds for odorants.
• Developing models which accurately predict dilution of
odorants by atmospheric dispersion.
• Methods to measure odors reliably and reproducibly.
Regarding odor measurement, our experience with the
Scentometer has been poor. It is not sufficiently precise or
accurate for regulatory use. The ASTM syringe and dynamic
olfactometer methods are better. The dynamic olfactometer
is easier to use than the ASTM syringe method and for that
reason should give more reproducible and accurate results
especially in the hands of untrained people.
In determining an odor's annoyance level, it is probably
unrealistic to define it in terms of an average response dose.
The general community and regulatory bodies will not accept
odor levels that half the population would complain about.
Some weighted dose-response level will be needed, for ex-
ample, the level at which 95% of the population would not
consider an odor offensive might be appropriate.
Similarly, in using dispersion models to predict ambient
odors, the variation in concentration with time, location, and
weather conditions should be considered. For criteria pollu-
tants the target concentration is not supposed to be exceeded
under the worst weather conditions at any location for a
specified averaging time. For odors it might be reasonable to
provide facilities where the target, ambient concentration is
not exceeded at any location 90% of the ti me for some appro-
priate averaging time. In order to do this, more work is needed
on the use of atmospheric dispersion models as they apply to
odors. Our experience from experimental studies with tracer
gases and odorants is that this is not simple or straight for-
ward. A key problem is that the averaging time for the human
response to odors is probably two orders of magnitude shorter
than that normally considered for short term dispersion
predictions.
I hope these comments are helpful. We encourage your ef-
forts to help develop reasonable odor regulations and your
efforts which highlight the need for additional work before
effective odor regulations car) be written.
Closure
W. H. Prokop
The critiques submitted by Messrs. Mulvaney and Mitchell
are important contributions to this session on odor control
regulations. Mr. Mulvaney ably defends the nuisance ap-
proach to odor regulation and also focuses his remarks on
other issues. Mr. Mitchell presents an alternate approach that
identifies a specific objective of odor regulations and offers
a regulatory standard to meet this objective. The written
comments by Messrs. Sterling, Turk, and Wykowski are also
significant additions to the position paper.
The TT-4 Committee had considerable differences of
opinion among its members regarding the various issues that
influence the development and promulgation of odor regula-
tions. It was difficult to portray an accurate consensus of the
Committee due to the diverse comments received. This
summary likewise represents a consensus of four members of
the Committee. It is interesting to note that, significant dis-
agreement exists in the critiques and written comments on
certain issues which are listed below.
January 1978 Volume 28, No. 1
59
-------
ODOR CONTROL REGULATIONS
The purpose of this summary is to focus on specific key
issues which are extracted from the critiques and comments
which have been presented. These key issues and their related
discussion are given below:
1. Issue: The objective of odor regulations is to eliminate
odor in the ambient air for all citizens in a community.
Discussion: Odor regulations should eliminate objec-
tionable odors. It seems to be unreasonable to outlaw all
odors that can be detected in the ambient air. For exam-
ple, national ambient air quality standards have been
promulgated for criteria health-related pollutants, such
as sulfur dioxide and carbon monoxide. Specific tolerances
for various levels are allowed in the ambient air for these
pollutants. Why should odors which are basically not
health-related have no tolerance in the ambient air?
2. Issue: Odor regulations must prevent an odor problem
from occurring. The regulation should include stack
emission limits that apply equally to all sources. Com-
pliance is required with the stack limits, whether com-
plaints are received or not.
Discussion: The emphasis in this approach is to provide
a clearcut standard for stack emission that applies to all
odor sources regardless of their location and proximity
to potential complainants. The position paper considered
valid complaints to be proof that an odor problem exists
in the community. Even though odors may be present, if
no complaints are received, then presumably an odor
problem does not exist. The blind application of rigid
single-number type limits to all odor sources appears to
be unreasonable, both from the standpoint of an agency's
manpower being used to enforce a questionable standard
and industry's investment in odor control equipment
being required where no odor problem exists. As discussed
in the position paper, adequate technology is not available
today to predict accurately the existence of a nuisance
based on stack emission data. As a result, stack emission
standards would be unnecessarily stringent to compensate
for this technical shortcoming.
State agencies currently have the regulatory mechanism
to prevent an odor problem from occurring before citizens
have complained. Any new odor source (or existing source)
is required to obtain a construction and/or operating
permit approved by the agency. At the time of application
for such a permit, the agency is in position to evaluate the
odor source, the proximity of neighbors, and make a
judgment as to the odor control requirements to be met
by the source. In fact, the section in the position paper
under "Compliance Program" could serve as a guide to
be used in processing an application for a permit. This
approach has the advantage of evaluating each source on
an individual basis and being able to relate the response
of potential complainants to the controlled odor emission
from the source.
3. Issue: 7x>ning parameters should not be included in odor
regulations.
Discussion: Zoning classifications are established for
different areas in order to provide stability of land use and
avoid incompatible uses. Background odors are an in-
herent part of our life and they vary in type and intensity
depending upon our exposure to them at home, at work
or elsewhere. It is reasonable to expect a higher back-
ground odor level to be present in heavy industrial and
rural ureas as opposed to residential communities. Cur-
rently, this distinction is made in certain state regulations
(Colorado, Illinois, Minnesota, and Missouri) that have
different ambient odor limits for residential, industrial
and rural areas. Further, existing noise control ordinances
throughout the U.S. are based upon different decibel
limits being established for different zoned areas.
4. Issue: Nuisance odor regulations should be retained until
such time that proven technology is available for ob-
taining reliable odor sensory data that can be related to
community acceptance or annoyance of a particular
odor.
Discussion: Our Committee agrees that odor nuisance
regulations should be retained for the present. The con-
cept of a community odor nuisance was presented in the
position paper in order to define more explicitly the ex-
istence of a nuisance. The number of valid complaints
received from separate households within a fixed time
period was no( specified in the paper because this could
vary for different zoned areas and for a more populated
community compared to a lesser one. The intent of this
approach was to eliminate isolated complaints that in-
volve supersensitive individuals. However, an agency may
wish to have an alternate approach for protecting a
"community" of one household.
5. Issue: The ASTM syringe dilution technique should be
retained for regulatory use until proven methods are
available to replace it.
Discussion: The ASTM syringe method is being modified
currently (see reference No. 10 in position paper) to
overcome inadequacies perceived to exist in the basic
method. Our Committee favors the development of im-
proved odor sensory measuring methods that include
dynamic olfactometers. As outlined in the position paper,
dynamic olfactometer methods have specific advantages
over the ASTM syringe method.
It is the hope of our Committee that the presentation of this
position paper and the accompanying discussion will stimulate
interest and further input on this subject from the concerned
parties: the public, industrial companies, and the regulatory
agencies. We encourage the submission of comments which
would be included in any future timely revision of this position
paper.
Mr. Prokop, Vice Chairman, APCA TT-4 Odor Commit-
tee, is with National Renderers Association, Inc., 3150 Des
Plaincs Avenue, Des Plaines. II, 60018. Mr. Mulvaney is Di-
rector. Lena I Services Branch, Ontario Ministry of the Knvi--
ronment, Toronto, Ontario, M4V IP5 Canada. Mr. Mitt-hell
is Special Assistant Attorney Cieneral, State of Minnesota,
Minnesota Pollution Control Agency, 19H.r> \V. County Road
B-2, Roseville, MN 5511:?. Mr. Sterling is Director, Wayne
County Department of Health, Air Pollution Control Divi-
sion, Detroit, Ml 4H207. Dr. Turk is in llie Department of
Chemistry, City College of the City University of New York,
New York, NY 100:11. Mr. Wykowski is with KXXON Re-
search and Kn^inecrini; Company. P.O. Mox 101. Klorham
Park, N.) 079:12. The Position Pnper was presented as Paper
No. 77-:W.;i at the 70th Annual Meeting of APCA at Toronto
in .lune 1977.
60
Journal of the Air Pollution Control Association
-------
Objective ODOR POLLUTION Control Investigations
NORMAN A. HUEY, Air Pollution Chemical Engineer,
LOUIS C. BROERING, Air Pollution Technician,
GEORGE A. JUTZE, Metropolitan Air Pollution Control Officer,
CHARLES W. GRUBER, Air Pollution Control and Heating Engineer,
Bureau of Air Pollution Control and Heating Inspection,
Department of Safety, Cincinnati, Ohio
e tremendous growth of in-
dustry in recent years has been responsi-
ble for much of the progress and
prosperity now enjoyed in the United
States. However, with this growth,
there also came new sources and new
aspects of air pollution. The aspect
which will be considered is that con-
cerning investigation of odors associated
with various manufacturing processes.
Investigation of odor complaints by
air pollution control personnel have
followed a rather well-defined procedure.
The investigation is initiated by a
telephone call from an irate citizen.
The description of the odor situation is
reduced in writing and given to the
inspector who proceeds to the troubled
area equipped with two things, his
endowed sensory perception and, at
times, a prior knowledge of potential
odor sources in the affected area.
Arriving at the scene of the com-
plaint, the inspector will mentally form
an impression of the severity of the
odor situation expressed as weak,
moderate, or strong. The inspector
can make an estimate of the wind
direction from a visible plume in the
vicinity and coupling with this his
knowledge of odors associated with
various manufacturing processes, he
can form a general opinion of the
direction and type of source. If he is
familiar with the area he may recognize
the true offending operation. How-
ever, if the odor has dissipated or if a
long time has lapsed between the
complaint and the investigation, then
an on-the-spot trace to the odor
source cannot be made.
In many cases the odor situation
has changed from the time; of the com-
plaint, so that a personal interview
with the complainant is necessary.
During the interview a description of
the odor situation is influenced materi-
ally by the emotional stability of the
* Presented at the 53rd Annual Meeting
of A PC A, May 22-20, IDtiO, Ncthcrla nil-
Hilton Hotel, Cincinnati, Ohio.
complainant. In such investigations,
the position of the inspector is that of
an arbitrator between management and
citizens. This position must be changed
to one of a true enforcement officer
through more adequate methods of
investigation.
The objective of any odor investiga-
tion is to obtain elimination or cor-
rection of the source. This can be
accomplished either through voluntary
action by plant management (a much
preferred procedure) or through legal
action.
If the former course of action de-
velops, certain stumbling blocks may
arise to deter the correction process.
Local management may have a very
co-operative attitude, but the cost of
control equipment may be prohibi-
tive. Often, between citizens and
plant management, there is a wide
difference of opinion as to the serious-
ness of the odor situation, and there-
fore, the need for corrective measures.
At times, because of the lack of positive
identification, errors in odor descrip-
tions, or a lack of accurate localized
meteorological information, doubt may
arise as to the suspected source and
positive proof will be demanded by the
suspected plant manager. This would
be particularly true in complex situa-
tions where many sources are located
within the same, area and the cost of
correction is high.
The latter course of action, that is,
legal procedures, may become necessary
because of a gross disregard for com-
munity relations by the source manage-
ment or it may be dictated by the
economic situation. The cost of cor-
rection may not be economically feasible
and a court decision is sought to es-
tablish in fact that a violation of the air
pollution ordinance has occurred and
that corrective measures art; a legal
necessity. In such cases the court
decision may fix the extent of correction.
The language of air pollution ordi-
nances dealing with odor nuisances is
broad and subjective. Only in recent
years has attention been given to
an objective criteria for outdoor odor
situations. However, to date, no
community has yet written objective
odor criteria into their Air Pollution
Control Ordinance. Therefore, legal
procedures are used to settle unresolved
differences of opinion between citizen
and source management ami to establish
whether or not a violation exists.
To thosi.1 engaged in air pollution
control work either for tin: govern-
ment or industry it is readily apparent
that more objective odor complaint
investigative procedures must be
developed. To accomplish this a
device or instrument for the deter-
mination of odor strength is of prime
importance. Techniques to point out
the offender from among a numl>er of
potential sources are also needed. \Vith
the development of objective procedures
and the enactment of reasonable ordi-
nances containing measurable odor
characteristics, the effort expended in
odor pollution correction will be more-
beneficial to the community.
The Nature of Ambient Odors
For the purpose of air pollution
control, odors an; classified in two
categories, ambient and source odors.
Ambient odors are those existing in the
general atmosphere and source odors
are defined as those at the poiut of
origin or at their point, of exit to the
general atmosphere. If odors occurred
only at their source and wore immedi-
ately dissipated there would be no
air pollution problem. However, this
situation does not prevail and thr
ambient odor problem arises. Tlv
specific ambient odor characteristics
of concern to the air pollution control
personnel art; quality, strength, and
occurrence.
(Duality of odor as yet is ed in
subjective terms such as :i degree of
pleasantness or by comparison with a
similar known odorant sudi as rotten
December 1960/Volume 10, Number 6
61
44 T
-------
Fig. 1. The Scentometer Model 1959A.
eggs, peppermint, etc. From the
standpoint of the air pollution officer
quality is a very complex issue and
cannot be described in objective terms.
For the present it must remain in
ordinances as broad word definitions.1
Odor strength can be expressed
objectively in terms of the amount of
air needed to dilute the given amount
of odorous air to the concentration at
which the odor is just detectable by the
human olfactory system. Strength
has been expressed in terms of odor
units,2'3 an odor unit being defined
as 1 ft3 of air at the odor threshold.
Other units of odor strength are the
threshold concentrations and multiples
thereof. The latter term is unitless
and, therefore, has certain advantages.
For example: an odor having a strength
of 10 odor units/ft3 is equivalent to
a strength of 10 times the threshold
concentration or 10 dilutions to the
threshold concentration (abbreviated—
10 D/T).
In discussing the strength of ambient
odors, it is well to look deeper into
their nature. Through repeated associa-
tion of the word ambient with odor, the
o
true meaning of ambient is usually
overlooked. Ambient odors are thought
of as those occurring out-of-doors;
however, the true meaning of the word
ambient as expressed by Webster is
"moving around" or "encompassing
on all sides." The first definition
should lead us to realize that the
strength of an ambient odor is changing
constantly with each air movement.
Therefore, strength of an ambient odor
loses meaning unless it is accepted as
the maximum strength found.
Occurrence, for purposes here, will be
defined in terms of duration and
frequency. It is often found that the
interval of duration of an ambient
odor is brief, for example two or three
min, and that the frequency is several
times per hour. This points out the need
for an expression of the interval of time
during which the sporadic durations
occur. Therefore, occurrence should
be expressed as having occurred at
intervals (giving average length of
time) with a given frequency during a
known period of time.
In summation:
1 Quality is a subjective characteristic
which is best discussed only in general
descriptive terms.
2 Ambient, odor strength should be
accepted a? the maximum strength
found. The unit of expression most
suitable for this work is the number of
times that the odor is as strong as its
threshold concentration or the num-
ber of dilutions with pure air needed
to dilute it to the threshold concen-
tration. This expression can be
written as D/T (dilution to thresh-
old).
3 Ambient odor occurrence includes the
average length of time at which inter-
vals occurred. Frequency during a
known period of these occurrences,
and the total length of time during
which the odor nuisance was present.
Measurements of Odor .Strength—-
the Scentometer
Measurement of the strength of
ambient odors in the past has not been
practical due to the lack of a reliable
measuring device. After investigation
of various instruments which might
have been capable of measuring ambient
odor strengths and finding all to be
lacking for this purpose, a new instru-
ment, called the "Scentometer," was
designed. The Scentometi'r is an
organoleptic instrument of the vapor
dilution type. The various dilutions
Table I—Scentometer Dilutions
Odorous Orifice,
Diam fjizc, In.
Fig. 2. Diagram of the top or the bottom sec-
tion, showing the purified air inlet.
'A
'A
'A
V.c
No. of Dilutions to
Threshold,
D/T
31
170
arc supplied by combinations of critical
size orifices. Purified air for the
purpose of dilution is supplied from
activated carbon beds. The mixture is
delivered to (lie olfactory tract for
appraisal through two no.sc pieces, air
being drawn through the instrument
by the action of the observer's lungs.
Figures 1, 2, 3, and 4 show the Scen-
tometer and its general arrangement.
Figure 5 is a list of the component
parts needed to build such an instru-
ment. The parts arc welded together
by using a mixture of dichlorocthylene
and plexiglas.
The current model Scentometer is
capable of four different dilutions and
thus divides odors by strength into
five groups. Experience has shown
that odors above 7 D/T will probably
cause complaints while those above
31 D/T can be described as a serious
nuisance if they persist for any length
of time. (Table I.)
The orifice sizes to accomplish these
dilutions are: purified air inlets of
Vz in. diam, leading to the carbon
beds, and odorous air inlets of V»>
'/«»'/«» and Vie in. diam leading directly
to the mixing chamber. The purified
air inlets are located in the top and bot-
tom sections of the Scentometer (Fig. 2)
and are separated from the filter
beds by a plenum chamber. The
odorous air inlets are located on the
front side (opposite the nose pieces)
of the Scentometer as shown in Fig. 4.
These are opened and closed by means
of tape tabs.
The size of the Scentometer body is
5 in. x 6 in. x 2.5 in. Figure 3 is a cross
section through the body. Seven
distinct layers are apparent. They are,
starting from the top: 'A plexiglas
wall, plenum chamber for air which
will be purified, activated carbon
filter, air chamber where odorous and
odorless air is mixed for delivery to
nose pieces, activated carbon filter,
plenum chamber for air which will be
purified, and J/« in. plexiglas wall.
The activated carbon which has
been used in the filter beds is that which
is obtained from coconut shells. The
life of this carbon depends upon the
frequency of use. From experience
we have found that these filters are
serviceable for at least three months,
when used on daily odor patrols. Re-
packing of the filters with new carbon
when necessary will not change the
dilutions to any appreciable amount.
This has been proved by air flow
measurements.
Measurement of ambient odor
strength is not a simple matter, how-
ever the difficulty docs not lie in the
instrument, rather it is inherent in the
variability of the ambient odors. Some
odors occur in narrow streams which
move about rapidly, some arc very
intermittent. To cope with these
442
62
Journal of the Air Pollution Control Aiiociotion
-------
variations, different methods of using
the Scentometer have been developed.
In the normal method of use, the
Scentometer is breathed through for a
minute with all odorous air inlets closed.
This period of time is to refresh or de-
fatigue the observer. Then the small
odorous orifice which gives the highest
dilution is opened and if no stimulus is
obtained the next larger orifice is
tried until a positive stimulus is ob-
tained. The strength of the odor
is designated as the dilution which
first gives the stimulus.
In cases where the narrow odor
streams occur, it is advisable to use a
different procedure. Move through the
odorous area either in an automobile
or on foot while breathing through the
scentometer set to obtain the highest
dilution. If no stimulus is obtained,
travel back through the area using
successively the next lower dilution
until an odor stimulus is obtained.
In cases when the odor is very
intermittent, breathe through the
Scentometer for a minute with all
odorous air inlets closed. Remaining
stationary, open the highest dilution
orifice and continue breathing through
the Scentometer for about 5 min.
If no stimulus is obtained during this
period of time, proceed successively
through the lower dilutions until a
stimulus is perceived.
Accuracy and precision of results
depend upon the human olfactory sense,
since the Scentometer is an organoleptic
measuring device. It has often been
said but never shown that the olfactory
sense is subject to variations from
person to person and/or from hour to
hour in the same person. Accuracy
and precision of results have always
been improved by increasing the number
of observers. The use of a panel of
observers is impractical for day to day
air pollution control work. Therefore,
to determine the necessity of panel
observations, the limitations of the
olfactory sense were investigated.4
Investigations were conducted using
successively stronger liquid dilution
sniff bottle samples.
These tests were done to determine
specifically the day to day variation
in the olfactory ability. Two persons
were given the same liquid dilution
scries on ten different days, both
subjects were influenced by head colds
of varying degrees. Results of these
tests are shown in Table II.
The variation in olfactory ability
between different individuals was inves-
tigated by giving five different tests
(odorants) to 17 different observers.
These, results are shown in Table III.
In these tests there was no screening
of observers. Observers were accepted
with or without head colds of any
degree. As long as it- is understood
that these variations and results can
December 1960/Volume 10, Number 6
:i>wc37.:.4'-4-:v<--!<:^
^>to:?.s.v« V,vv-.^^^
^
Fig. 3. CroM section, showing the poiitiom of carbon filters and the nose pieces.
O
O
Fig. 4. Diagram of the frontpiece showing the positions of the odorous air inlets.
Material
Plcxiglas
Brass Screen
Solution
Activated Carbon
Glass Tubing
Plastic Tape
Pieces Length Width Thickness
2 6.0 5.0 0.25
8 5.0 0.5 0.25
4 5.5 0.375 0.25
4 5.0 0.375 0.25
2 5.5 0.75 0.25
2 5.0 0.75 0.25
4 6.0 5.0 —
Containing 256 holes (approximately 1 ram) per sq in.
of Plexiglas in Ethylene Dichloride (30% by vol) ap-
proximately 50 ml needed
Approximately 6 oz/Scentomcter Barneby-Cheney Co.
Length 12 in. and diam 10 m
2 ft
Fig. 5. Scentometer parts list.
Table II
Observer
Medium Threshold
Liquid Dilution
Threshold Range
7.5(10')
2.9(10')
4.3 (10') to 13.0(10')
1.3 (10') to 6.4(10')
Table III
Test
Odorant
Oil of Turpentine
Mercaptan
nimeUiylaniine
Synthetic
Body Odor"
Svnthetic
' Hospital Odor"
Medium Threshold
Liquid Dilution
2-t (10=)
2.-I (10')
0.39(10')
7<>.S(103)
23.4(10")
Threshold Range
4(10:) to 100(10=)
O.S (10') to 6.4 (101)
0.13(10">)to 2.0(10*)
25. 6 (101) to 205 (10')
0.4 (10s) to 85(10*)
1 Supplied by Airkem, Inc., New York, N. Y.
63
443
-------
Table IV
Table V—Effect of Time of Year
Test Odorant
Oil of Turpentine
Mercaptan
Dimethylamine
Synthetic
Body Odor
Synthetic
Hospital Odor
Medium Threshold
Liquid Dilution
24(10J)
2.7(10*)
0.34 (10s)
68(10')
20(10*)
Threshold Dilution
Range
8(10") to 64(10")
1.1 (104) to 6.4(104)
0.13(104)to 0.84 (10s)
34(10') to!3C(10>)
6.4(10") to 51.2(10")
be expected and are acceptable, no
panel results nor screening of observers
are neeessarj'.
By a 50% screen of observers, results
in Table III can be changed to those
in Table IV.
These figures show that with some
screening of inspectors, variations in
olfactory ability is negligible when
using the Scentometer. This is because
the olfactory variations are within the
limits of the measurement intervals
incorporated in the design of the
Scentometer.
Source Location
The basic fact that odor travels
downwind substantiates the fact that
wind direction in an odorous area will
Fig. 6. Equipment for the determination of
wind direction.
Fig. 7. Verification of a suspected source:
The buildings in black are the suspected source,
' the black dots at the end of the lines represent
the observation points, and the lines represent
the wind direction at the time of the observation.
point out the odor source. In the inves-
tigation of odor complaints, to sub-
stantiate the accusation of the suspected
source and/or to determine an un-
known source, accurate wind direction
data gathered at the odorous area are
important.
The method used to determine wind
direction in the odorous area is that of
low flying balloons inflated with helium.
The procedure is as follows: While in
an odorous area inflate a small balloon
with sufficient gas so that the balloon
will rise slowly, release and watch its
path with a compass. Point the "N"
mark on the compass at the balloon,
read the degree number at the south
end of the compass needle. Subtract
this reading from 360 to get the wind
direction and degrees. Figure 6 is a
photograph of the equipment needed to
gather wind direction data.
Figures 7 and 8 give examples of
actual cases using data from multiple
balloon releases. Figure 7 contains
11 wind directional lines which were
obtained during 11 different complaint
situations against the same plant.
The observation points are shown as
dots and the lines from the dots rep-
resent the wind direction or the
direction from which the odor was
coming. The suspected source is
shown in black. These 11 deter-
minations give conclusive evidence
that the suspected plant is the true.
source.
Figure 8 is an example of deter-
minations of an unknown source within
Month Number of
of Year Complaints
January
February
March
April
May
June
July
August
September
October
November
December
1
G
<)
14
28
44
34
2
1
Number of
N'uisam-i;
Occurrence*
i
4
4
9
16
18
18
2
1
A'o.'e: The number of nuisance occur-
rences refers to the number of different
days on which complaints occurred. Note
that 86% of the complaints and 84% of the
occurrences happened during the months
of June, July, August, and September.
a multiple source plant. There are
approximately 24 individual chemical
manufacturing buildings within this
one complex company. The three
wind directions obtained during three
different occurrences have narrowed the
field down to four buildings. Inde-
pendently, tho plant personnel then
traced the source to the plant noted on
the di-'igram in black, confirming the
source identification by the wind tri-
angulation method.
Standard Procedure for Ambient
Odor Investigation
In summary of the previous disc-us-
sions, it seems appropriate to suggest
that the following consideration* on
the procedure for the investigation of
odor complaints be established:
/ Complaint: Information for the
record obtained from the complainant
should contain the following informa-
tion: Name and address of the complain-
ant, time and location of the complaint,
a description of the odor (if unable to
describe the odor, have the complainant
liken it to an odor which he can de-
scribe), and finally, the suspected source.
Fig. 8. Detection of an unknown source: The building in block was the unknown source, the black
dots at the end of the lines represent the observation points, and the lines represent the wind direction
at the time of the observation.
444
64
Journal of the Air Pollution Control Association
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2 Observation: The observation re-
port should include the following
detailed information: Location and
extent of the odor situation, recorded
times of all measurements taken during
the investigation, the type of odor,
occurrence of the odor in terms of
frequency and duration, the source
suspected by the inspector, distance
and range that the odor situation
exists from the suspected source, and
the angle formed at the suspected
source from north to the location of
the odor.
3 Meteorology: Determine the local-
ized wind direction at the site of the
ambient odor and record this direction
in degrees from north.
4 Plant Interview: Once a deter-
mination lias been made as to the
source of the odor situation, the name
of offending source as well as the
responsible supervisory employee on
duty should be obtained. The inter-
view with the supervisor should reveal
how and why the odor situation occurred
and the nature of corrective measures
which will be taken to abate the odor.
5 Complainant Interview: A report on
the odor investigation should then
be made to the complainant. At this
time it is wise to obtain any additional
information from the complainant which
would tend to clarify the complaint
situation. At a later date, the complain-
ant should be notified as to the progress
of action which is being taken on the
complaint situation.
Having obtained the information as
outlined above, the odor investigator
may return to his office and log much
of this data on area maps. Assembly
of the facts in this manner will show
the relationship between the complaint
location, location of the observed odor,
wind direction and the location of the
suspected or unknown source. With
this information at hand, the courses of
action to obtain correction within the
policies and authority of the air pol-
lution control agency are established.
Meteorological Effects on Odor
Nuisance Occurrences
Meteorology plays an important
part in the build-up of odor nuisance
occurrences. In an effort to have a
better understanding of the weather
both favorable toward and against.
such occurrences, the following study
was made. The meteorology at the
time of complaints was collected and
grouped to show its effects. All mete-
orological data were taken from the
records of the U. 8. Weather Bureau
Station which is loeated some 15 miles
from the meat rendering plant, against
which all of those complaints wore
filed. (See Tables V through XII.)
In summary, the weather conditions
to watch as those most conducive to
Table VI—Effect of the Day of the
Week
Table VII—Effect of the Time of Day
Day of
Week
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Number of
Complaints
19
15
8
10
17
34
41
Number of
Nuisance
Occurrences
7
11
6
7
10
11
18
Time
of Number of
Day Complaints
0000 to
0600
0600 to
1200
1200to
1800
1800 to
2400
12
29
44
53
Number of
Nuisance
Occurrences
9
23
24
32
Note: During the middle of the week
fewer occurrences and complaints hap-
pened. Saturday is the day of most fre-
quent complaints and most numerous odor
occurrences.
Note: Only 8.7% of complaints and
only 10% of the odor occurrences came
during the first quarter of the day.
Table VIII—Effect of Temperature
Temperature
Range
Oto44
45 to 49
50 to 54
55 to 59
60 to 64
65 to 69
70 to 74
75 to 79
80 to 84
85 to 89
90 to 94
95 to 100
No. of Complaints
During 1958 and
1959
0
2
3
4
5
26
33
34
13
10
4
0
No. of Hours
of Temp Occ
6184
1262
1121
1118
1493
1795
1957
1228
817
472
73
0
Ratio: No.
Hours/No.
Corap
Inl
631
374
280
299
69
59
36
63
47
IS
Note: The critical temperatures for these odor nuisances are above 65°F.
temperatures result in more frequent complaints and nuisances.
Table IX—Effect of Atmospheric Pressure
Higher
Pressure Range
(In. Hg)
0 to 2SS4
2885 to SO
90 to 94
95 to 99
2900 to 04
05 to 09
10 to 14
15 to 19
20 to 24
25 to 29
30
No. of Complaint*
During 1958
.and 1959
1
6
21
9
18
25
18
15
9
5
4
No. of Hours
of Pressure
Occ
1234
790
1424
1714
2032
2260
2090
1/70
1720
844
1622
Ratio: No.
Hours/No.
Comp
1234
132
68
190
113
90
116
118
101
170
406
Note: Very few complaints were received when the atmospheric pressure was below
28.84 in. Hg.
Table X—Effect of Relative Humidity
No. of Complaints
Relative During 1958 and
Humidity Range 1959
0 to 30
30 to 49
50 to 69
70 to 79
80 to 89
90 to 100
0
27
47
24
IS
IS
No. of Hours of
R.H. Occurrence
453
2974
5186
31S4
3007
269S
Ratio: No.
Hours/No. Comp
Inf
110
110 s
132 s
167
150
Note: Hours of low relative humidity have more frequent complaints per hour.
Table XI—Effect of Wind Velocity
Range
Wind Velocity,
Mph
0 to I
5 to 14
15 to 24
25 to inf
No. of Complaints
During 1958 and
1959
25
!I5
17
0
No. of Hours
of Vel Occ
35S4
11105
2710
ill
Ratio: No.
Hours/No. Comp
113
117
161
?
Nctr: Wind velocity had no effect on the number of hours per complaint.
December 1960/Volume 10, Number 6
65
445
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Table XII—Effect of Changing Temperature, Pressure, and Relative Humidity
Temperature .
Type of No. of % of
Change Complaints Total
lucre-using
Static
Decreasing
34
19
79
26
14
CO
No. ofressurc %Qf
Complaints Total
64
37
30
49
28
23
. — Relative Humidity — •
No. of %of
Complaints Total
69
15
48
52
II
37
Note: ()>i a percentage basis, decreasing temperature, increasing pressure, and
increasing relative humidity cause more frequent complaints to be received.
nuisance occurrences in this type of
industry are:
/ Months of. the year—June, July,
August, and September
g Buys of week—Friday, Saturday,
Sunday, and Monday
3 Time of day—the P.M hours
4 Temperature—65"andover
5 Pressure—28.84 in. Hg and over
6 Relative humidity—particularly
the lower ones
7 Wind velocity—has no significance
8 Changing temperature—decreas-
ing
9 Changing pressure—increasing
10 Changing relative humidity—
increasing
The data in this study were gathered
so that parallels from it might be
drawn. By watching these meteorolog-
ical factors, odor nuisance occurrences
can be forecast with some degree of
accuracy. These results, however, were
obtained specifically on a meat render-
ing plant operation and care must be
taken when drawing parallels with
other types of industry.
REFERENCES
1. Charles W. Gruber, G. A. Jatze, and
Norman A. Huey, "Odor Measurement
Techniques," Proceedings of the 52nd
Annual Meeting of APCA, No. 59-08,
(June, 1959).
2. ASTM Committee D-22, ASTM Stand-
ards on Methods of Atmospheric
Sampling and Analysis, American So-
ciety for Testing Materials, p. 40,
Philadelphia, Pa. (1959).
3. E. Dewey and F. Byrd, "Tentative
Method of Test of Odor Concentra-
tion in Air and Gases," Procter and
Gamble Co., Cincinnati, Ohio (1955).
4. Xorman A. Huey, Louis C. Broering,
and Charles W. Gruber, "Odor Meas-
urement Techniques II," Bureau of Air
Pollution Control and Heating Inspec-
tion, Cincinnati, Ohio (1959).
66
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