JULY 1974
EPA-450/3-74-046-b
AIR POLLUTION
*
CONSIDERATIONS
IN RESIDENTIAL PLANNING
VOLUME II:
BACKUP REPORT
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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EPA-450/3-74-046-b
AIR POLLUTION
CONSIDERATIONS
IN RESIDENTIAL PLANNING
VOLUME II:
BACKUP REPORT
by
T. M. Briggs, M. Overstreet,
A. Kothari , and T. W . Devitt
PEDCo-Environmental Specialists, Inc.
Suite 13, Atkinson Square
Cincinnati, Ohio 45246
Contract No. 68-02-1089
EPA Project Officer: John Rob son
Prepared for
DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT
Washington, D. C. 20410
and
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, N. C. 27711
July 1974
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This report is issued by the Environmental Protection Agency to report
technical data of interest to a limited number of readers. Copies are
available free of charge to Federal employees, current contractors
and grantees, and nonprofit organizations - as supplies permit - from
the Air Pollution Technical Information Center, Environmental Protection
Agency. Research Triangle Park, North Carolina 27711; or, for a
fee, from the National Technical Information Service, 5285 Port Royal
Road, Springfield, Virginia 22161.
This report was furnished to the Environmental Protection Agency
by PEDCo-Environmental Specialists, Inc. , Cincinnati, Ohio 45246,
in fulfillment of Contract No. 68-02-1089. The contents of this report
are reproduced herein as received from PEDCo-Environmental
Specialists, Inc. The opinions, findings, and conclusions expressed
are those of the author and not necessarily those of the Environmental
Protection Agency. Mention of company or product names is not to
be considered as an endorsement by the Environmental Protection
Agency.
Publication No. EPA-450/3-74-046~b
11
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ACKNOWLEDGEMENT
This report was prepared for the U.S. Environmental Protec-
tion Agency and the Department of Housing and Urban Development
by PEDCo-Environmental Specialists, Inc., Cincinnati, Ohio and
Vogt, Sage and Pflum, Cincinnati, Ohio. Timothy W. Devitt
was the PEDCo Project Manager. Principal investigators were
Mr. Terry Briggs, Mr. Mace Overstreet and Mr. Atul Kothari.
Mr. John Robson was Project Officer for the U.S. Environ-
mental Protection Agency and Mr. Charles Z. Szczpanski served as
Project Officer for the Department of Housing and Urban Develop-
ment. The authors appreciate the assistance and cooperation
extended to them by members of the U.S. Environmental Protection
Agency and the Department of Housing and Urban Development.
111
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The procedures presented in the manual should not be considered
accurate estimating methods. They represent a first attempt to
present simplified procedures for determinging the impact of air
pollutants at residential developments. The procedures presented
in the manual have not been tested empirically to determine their
validity.
The manual has been written for-use, primarily by residential
planners and assumes the user has little or no formal training in
air pollution and related scientific disciplines.
IV
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TABLE OF CONTENTS
Page
vii
LIST OF FIGURES
LIST OF TABLES
1: INTRODUCTION
Scope of the Project ^
Objectives of the Manual 2
Content of Report
2: SELECTION OF POLLUTANTS
3: AIR QUALITY STANDARDS
4: SELECTION OF POLLUTANT SOURCES
19
Outdoor Pollution Sources
Indoor Pollution Sources
5: TRANSPORT AND DISPERSION OF AIR POLLUTANTS 2?
27
Dispersion 2?
Identification of Worst-Case Conditions 35
Significant Sources
6: POLLUTANT EMISSION AND DISPERSION PROCEDURES 39
Roadways . .
Point Sources 47
Space Heating 52
Parking Lots 54
Airports
7: ANALYSIS FOR SITE DESIGN 63
Research 6_
Conclusions
v
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Page
8: INDOOR-OUTDOOR RELATIONSHIPS 71
„ 71
Research 71
Findings 73
Theory and Modelings 80
Operational Assumptions g^
Relationships 87
Re c ommend at ions
9: CONCLUSIONS 97
Summary of Results gg
Limitations ^g
Present Usefulness of the Manual gg
Recommendations for Further Study
APPENDIX 101
VI
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LIST OF FIGURES
Figure Page
5-1 Coordinate system showing distributions in
the horizontal and vertical.
59
6-1 Computerized point source model.
8-1 Schematic representation of outdoor-
indoor model.
81
8-2 Typical outdoor pollution profile.
A-l Average speed correction factors.
VI1
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LIST OF TABLES
5 -1 Key to Stability Categories
Page
28
A-l 1975 FTP (Hot Operating) CO Emission Factors 101
1 0?
A-2 Light Duty Gasoline-Powered Vehicle Model
Emission Ratios
IX
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1.0 INTRODUCTION
SCOPE OF THE PROJECT
The contract for this project calls for production of two
documents: (1) a manual for use by land-use planners, engineers,
or designers in evaluating air pollution aspects of residential
development, and (2) a backup technical report for use by profes-
sional air pollution specialists and urban planners, citing
the research materials used in preparing the manual, outlining
development of procedures and models, and presenting recoiranenda-s
tions.
The principal objective for the project is to identify
site design practices that will reduce exposures to air pollutants
in residential environments, with resulting benefits to human
health. Environmental impacts other than human health effects
are not considered.
OBJECTIVES OF THE MANUAL
The manual was developed as a practical calculation proce-
dure for the residential planner, who is assumed to have limited
background in the scientific/technological aspects of air pollu-
tion control. We therefore omit theoretical explanations of
the procedures. To the extent possible, procedures are presented
in an orderly, step-wise fashion to reduce confusion and the
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possibility of error.
Following are some of the objectives that guided preparation
of the manual.
1. The methodology should enable the planner to assess
impacts of air pollution sources on any proposed residential
configuration likely to be found in this country. The procedures
must therefore be valid for a wide range of cases, encompassing
variations in locale and type of housing.
2. The manual should be concise and easy for the planner
to use.
3. The manual should outline recommended practices for
design of building sites and for planning of structural and
mechanical features of the buildings. Sub-objectives are that
the practices recommended should be practical, economical,
and compatible with other characteristics ordinarily desired
by the land-use planner or developer.
CONTENT OF THIS REPORT
This final report presents the rationale that underlies
the procedures given in the manual. Section 2 considers the
technical basis for selection of particulates, sulfur dioxide,
and carbon monoxide as the air pollutants to be evaluated and
for the exclusion of other significant air contaminants.
Section 3 describes development of the pollutant standards
presented in the manual by adapting various elements of the
National Ambient Air Quality Standards.
Section 4 presents the basis for selection in evaluating
and outdoor pollutant sources to be considered in evaluating
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pollution impact at a residential site.
Section 5 describes the basic dispersion model as it
is applied to the different pollutants and meteorlogical condi-
tions .
Section 6 considers development of emission data for
the various classes of outdoor pollution sources presented in
the manual.
Section 7 describes in detail the development of a model
for conversion of outdoor to indoor pollutant levels, citing
pertinent empirical data.
Section 8 describes briefly the background information
on which the recommended design practices are based. This informa-
tion is recognized to be both limited and essentially qualitative.
Section 9 evaluates the over-all project, indicating the
perceived strengths and weaknesses, and giving recommendations
for further research efforts toward evaluation and reduction
of air pollution impact at residential sites.
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2 SELECTION OF POLLUTANTS
For this study, consideration of the impact of air pollutants
is restricted to their effects on human health. Effects on
plants and materials are not evaluated, primarily because including
these elements would further complicate the procedures of overrid-
ing concern: those for evaluating effects on human health.
Pollutants selected for evaluation in the manual are particu-
lates, sulfur dioxide, and carbon monoxide. Their effects
on human health are fairly well established, and they are widely
dispersed in the atmosphere. Additionally, they are the only
pollutants whose atmospheric dispersion can be calculated for
local impacts and short time durations. They are among the
few pollutants for which reliable emission data are available.
They are the only pollutants for which we can fairly reliably
determine atmospheric concentrations that can be correlated
with human health effects.
Several significant pollutants and pollutant groups, known
to be hazardous to human health, are excluded. In the following,
we consider these pollutants and the reasons for their exclusion.
1) Hydrocarbons - We evaluated in detail the procedures
for calculating hydrocarbon levels, but determined that in
the context of residences the sources for which hydrocarbon
-------
emissions could be calculated are too close to the receptor
to create significant deleterious health effects. The national
air quality standards for hydrocarbons are based on their ability
to interact in the atmosphere to form photochemical oxidants.
The normal time required to form significant oxidant levels
is in the order of a few hours. Procedures in the manual,
however, can adequately determine the impact only of pollutants
within a few kilometers; at this close range a hydrocarbon dis-
charge does not have sufficient time to participate in formation
1 2
of oxidants to an appreciable extent. '
2) Nitrogen oxides -^Nitrogen oxides are strongly implicated
in acute and chronic^ respiratory disease and in systemic effects.
Additionally, they are precursors of photochemical oxidant forma-
tion in the atmosphere. Unfortunately, since retraction of
the EPA method for sampling and analysis of nitrogen oxides
in June 1973, no reliable and accepted analytical method is
available. For that reason, nitrogen oxides are not included
in the calculation procedures. It is recommended that procedures
for determining impact of nitrogen oxides be added to the manual
2
when reliable data and methods become available.
3) Oxidants - Although oxidants constitute a major class
of air pollutants, they are secondary pollutants and are thus
beyond the scope of the manual.
4) Particulate sulfates - It appears that the degradation
products of sulfur dioxide, namely particulate sulfates and
sulfuric acid aerosols, are more potent irritants than S02 itself.
Again, however, particulate sulfates are secondary pollutants
-------
and their concentrations cannot be determined adequately by
procedures of the manual. The calculated levels of SO2 therefore
must be used to estimate particulate sulfate levels. Because
of the paucity of available data, the validity of this assumption
2
is not known.
5) Carcinogenic air pollutants - A .number of known carcino-
gens have been shown to occur in polluted air. These include
polynuclear aromatics; azaheterocyclic compounds; various metals
such as nickel, chromium, and arsenic; asbestos fibers; and
radionuclides. At present no method is available for determining
2
the levels of individual carcinogens, or of total carcinogens.
6) Lead - Airborne lead represents a serious hazard mainly
in urban areas. Since airborne lead compounds result mainly
from auto emissions, the highest concentrations occur in areas
adjacent to heavily trafficked roadways. No adequate predictive
model of atmospheric lead levels is presently available. It
appears, furthermore, that lead in ambient air is not the major
3 4
source of the current health problems related to lead. '
CO levels should be a fairly good guide to prediction
of relative lead levels, since emissions of both are pyedominently
from auto exhaust.
7) Asbestos - Inhalation of high levels of asbestos fibers
has been associated with asbestosis and cancer. A long latent
period of 20 years or more usually occurs between the initial
exposure and the recognition of cancer; the latent period for
asbestosis is often- much shorter. At present, the only epidemi-
ological data showing a definite health hazard from exposure
-------
to asbestos fiber relate to industrial workers with exposure
levels far higher than those to which the general public is
exposed.
A residential development adjacent to an asbestos fiber
processing plant may receive high exposure levels, but we have
no data to verify this. Additionally, there is no adequate
and reproducible analytical method for determining asbestos
fiber concentrations in air. Section 6.0 of the manual, Recom-
mended Design Practices, includes no caution against the use
of asbestos insulation as a construction material. There are
no data to indicate that the resulting potential levels of expo-
sure present any health hazard; or in fact, whether any exposure
does result. Further, since asbestos insulation affords some
degree of fire protection and conserves thermal energy, any con-
demnation of its use in construction must be well justified.
The manual presents a list of hazardous air contaminants
and of industries with which they are commonly associated (Appen-
dix B). This material is included primarily as a warning of
the potential local health hazards presented by a large number
of pollutants. The distance at which these pollutants should
be considered by the planner is designated as 2 kilometers,
with the proviso that realistic hazard evaluation can be obtained
through the local air pollution control agency. The data in
g
Appendix B were obtained from Sittig.
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REFERENCES
Air Pollution, Vol. I, Ed. Stern, A.C., 2nd Edition, Academic
Press, 1968.
Summary of Proceedings, Conference of Health Effects of Air
Pollution, National Academy of Sciences, prepared for the
Committee on Public Works United States Senate, U.S. Govern-
ment Printing Office, November 1973.
Kehoe, R. A. Toxicological Appraisal of Lead in Relation to
the Tolerable Concentration in the Ambient Air, J. Air
Pollution Control Association. 19,690 (1969).
An American Chemical Society Symposium, Air Quality and
Lead. Environmental Science Technology. 4,217 (1970);
4,305 (1970).
Stern, A. C. et al., Fundamentals of Air Pollution, Acedemic
Press, 1973.
Cralley, L. J. Epicemiologic Studies of Occupational Dis-
eases, in: Industrial Environmental Health, The Worker and
the Community (L. V. Cralley ed.), Academic Press, 1972.
Bloomfield, B. D. and Barrett, J. C. Hazard Evaluation and
Control, ibid 6.
Sittig, M. Pollutant Removal Handbook, Noyes Data Corp.,
1973.
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3 AIR QUALITY STANDARDS
The initial approach to defining air quality standards for
residential developments was to present acceptable, marginally
acceptable, and unacceptable levels for each pollutant. The
hope was that within these ranges we could specify permitted
types of human exposure. The air quality standards, however,
were set to protect the most susceptible segment of the population;
thus a safety factor is already built into the existing standards.
Because the available experimental exposure data are sparse and
difficult to interpret, one standard concentration for each pollu-
tant was all that could realistically be defined.
The national air quality standards for short-term exposures
are expressed as the level not to be exceeded more than once
per year for that time interval. Since the methods presented
in the manual are intended for general, nationwide application,
we avoided dealing with extreme local meteorological conditions.
Accounting for such extreme conditions would have complicated
presentation of the emission data and the dispersion models.
We therefore considered only moderate meteorological conditions,
defined as the worst case not to be exceeded more than 3 percent
of the time periods, .per year. We applied the Larsen mathematical
model to adjust the national standard to the 3 percent level.
11
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The following equation from Larsen was used to make the trans-
formation :
where: Cn = pollutant concentration of adjusted standard
at 3 percent level
Cs = national air quality pollutant concentration
Zq = Number of standard deviations between the 3
percent level and the median
Zs = number of standard deviation between the
national standard and the median
Sq = standard geometric deviation
Use of this equation requires knowledge of the standard geomet-
ric deviation, which is a function of location. The standard geo-
metric deviation data presented by Larsen for different U.S. cities
were used to arrive at average standard geometric deviation levels
for determining the adjusted pollutant concentration (C ) standard.
Following are listed the relevent national air quality stan-
dards not to be exceeded more than once in the given time period
per year and the adjusted standards not to be exceeded more than
3 percent of the time period per year :
National air Adjusted
quality std. standard
CO duration - 1 hr 1 hr
level mg/m 40 15
duration 3 8 hr
level, mg/m 10
SO2 duration 3 24 hr
level yg/m 365 (primary)
duration 3 3 hr 3 hr
level, yg/m 1300 (secondary) 450
Particulates duration 24 hr 24 hr
level yg/m3 260 210
12
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The Preliminary Evaluation presented in Section 2 of the
manual employs annual average air quality standards for particu-
lates and S02. Continuous Air Monitoring Program (CAMP) data
is used for this analysis. Annual average CAMP data is used
since this is more readily available data interpreted to gen-
erate worst case not exceeded more than once per year or 3
percent of the time period.
A few words are appropriate here concerning the known health
effects of the three pollutants and their relation to the standards,
The present national carbon monoxide standard is based
on the atmospheric concentration necessary to result in a 3 percent
blood carboxyhemoglobin (COHb) level. This is the level at which
predictible angina has been found. At the 3 percent CoHb level,
patients suffering from angina pectoris develop pains sooner
after exertion. The following data show the relationships between
atmospheric carbon monoxide levels and the percentage of COHb
2
for 1-hour and 8-hour exposures :
1-hour exposure
% COHb Rest Light activity Exercis*e
46
73
99
2.0
3.0
4.0
90
143
196
mg/m3 CO
57
90
123
8-hour exposure
2.0
3.0
4.0
18
29
39
18
24
33
15
23
31
13
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These data show that the national CO standard provides a
substantial margin of safety.
It is known that altitude significantly affects the COHb
level and can cause serious problems when persons having coronary
artery disease go to high altitudes. Such people can, however,
become acclimatized,, and the effect is moderated with time.
The manual does not account for this effect, since the EPA has
not modified the CO standard in this regard. The manual does
emphasize that the procedures presented cannot be applied to
unusual terrains, extremes of climate, and the like.
Health effects of paticulate and S02 are more complex and
not well understood. No well-defined physiological responses
to these pollutants have been observed. It does appear, however,
that the products of their interaction, particulate sulfates,
are significantly more hazardous.
The S02 standard presented in the manual is a 3-hour value
derived by combining the Federal 24-hour primary standard and
the 3-hour secondary standard. Again, we applied Larsen's statis-
tical techniques. Although the secondary standard is not intended
to protect human health directly, it is less difficult to meet
than the 24-hour primary standard.
The manual's paritculate standard was not adjusted to the
3 percent level by Larsen's technique, since that procedure would
yield unrealistically low levels. The standard selected (210
yg/m ) lies between the Federal primary standard (260 yg/m )
and the secondary standard (150 yg/m3). To improve the accuracy
14
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of the pollutant dispersion models/ we tried to establish short-
term standards whenever possible. For particulates, however,
a time period of less than 24 hours was not feasible, since no
adverse health effects could realistically be considered for
2
a shorter time period.
15
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REFERENCES
Larsen, R. I., A Mathematical Model for Relating Air
Quality Measurements to Air Quality Standard, EPA,
AP-89, 1973.
Personal communication with Dr. Love, National Environ-
mental Research Center, Human Studies Lab., Research
Triangle Park, N.C.
Vaughn, D. J. and Stanek, E. J. Sulfur Dioxide Standards-
Primary More Restrictive than Secondary? Journal of the
Air Pollution Control Association, Vol. 23, No. 12,
December 1973.
Air Pollution, Vol. I, Ed. Stern, A.C., 2nd Edition,
Academic Press, 1968.
17
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4 SELECTION OF POLLUTANT SOURCES
OUTDOOR POLLUTION SOURCES
The manual presents procedures for estimating levels of
pollutants from several sources: roadways, parking lots, point
sources, space heating, and airports. These are the source
categories known to emit particulates, S02 > and CO in such a
way as to exert significant localized, short-term impact on nearby
receptors. Thus their proximity to a residential development
could entail hazards to health.
Motor vehicles represent by far the largest sources of carbon
monoxide. Under the meteorological conditions producing high
concentrations of CO from roadways, the only other significant
local sources of CO are parking lots. The major local sources
of particulates and SO2 are activities involving the burning
of fossil fuels. The major emitters, such as individual industrial
plants, are listed in the NEDS point source inventory. The smaller
but more widespread area sources are mainly space heating units.
Although airports constitute significant local sources of
carbon monoxide, particulates, and hydrocarbons, no simple and
accurate dispersion model allowing manual computation is available.
Thus the procedure for estimating potential significance of air-
ports was included as a safeguard against use of the manual to
19
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evaluate a residential site close to a major airport.
Following are types of emission sources not included in
the manual and the reasons for their exclusion.
1. Construction and demolition. These tend to- be short-
term projects that should not affect the pollutant levels at
a site on a continuous basis. Also, these emissions can be
estimated only very crudely.
2. Shipyards. Emissions from major shipyards can have
a significant impact on local receptors. Shipyard activities,
however, would affect only a few areas in the country. Further,
the emission rates are poorly defined, and meteorological condi-
tions at shipyard sites tend to deviate significantly from the
average conditions considered in the manual. Thus, the manual
specifies that professional help should be sought in evaluating
sites located close to a large body of water.
3. Railroads. Emissions from trains averaged over the
time periods specified in the standards are not significant.
Generally, the only significant emissions are from the railyards
The emission rates from railyards are poorly defined as a rule;
large railyards are considered, however, among the point sources
recorded in the NEDS forms.
4. Emissions from natural phenomena such as forest fires.
There is no acceptable way of measuring these emissions. For
short-term standards, their contribution should be negligible.
20
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INDOOR POLLUTION SOURCES
Research
Gas Cooking
The evidence is clear that gas-fueled cooking stoves add measur-
able increments of carbon monoxide and oxides of nitrogen to
indoor air. Yocom et al. (1969) found that gas space heaters
did not affect indoor concentrations of CO in test homes, but gas
2
cook stoves did. W. C. Eaton et al. (1973) measured concentra-
tions of N02 in the vicinity of the kitchen gas ranges with
the cooktop or the oven in use. High concentrations occurred
near the stove even with a hood-type exhaust vent in operation.
This study also noted a positive correlation between usage of
gas stoves and the incidence of lower respiratory infections
among 146 Long Island families. The sample was small, and the
time period covered only one season. Without further evidence
from more definitive studies one cannot state categorically that
gas-fueled cooking is a causative factor in lower respiratory
illness.
Particulate Generation
Significant particulate emissions indoors are due to cooking
and smoking. Particulates that settle are regenerated and kept
in suspension by activities of the people inside the house.
These relationships are adequately documented by Benson et al.,
and are not discussed further here.
21
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SO2 Generation
No study indicates significant indoor generation of S02 that
is not directly traceable to faulty heating equipment.
Recommended Measures
Calculations presented in the manual account for only gas-fired
cooking units and attached garages. These calculations entail
tack-on factors for attached garages or gas cookstoves. In for-
mulating the recommended design procedures, we strongly considered
a flat recommendation against gas cooking appliances, but decided
that present data are not yet strong enough to warrant such a
recommendation. If further significant data are gathered in
support of the Eaton study, banning of gas cooking appliances
appears in order. For the moment the manual recommends inclusion
of outdoor-vented hood fans.
A number of other indoor pollutant generators, some of which
we believe warrant consideration, were not included in our
analysis:
1. Housecleaning, smoking of tobacco, and turbulence of
4
movement are shown to generate particulates indoors, but these
activities are not controllable by the builder and at present
are not well quantified.
2. Emissions from furnaces, fireplaces, hot water heaters,
or other generators attached to a flue are considered insignifi-
cant, provided the flue connections are in proper order. '
No data were found for evaluating the impact of fireplaces.
3. Gas clothes dryers also are excluded because of the
22
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lack of dependable data. With adequate venting to outdoors,
the dryer is theoretically an insignificant source.
4. Various aerosol sprays are reported to be potential
health hazards. Again, use of these sprays is not controllable
by the builder.
Garages
Attached - The manual recommends a positive sealing door
between an attached garage and living space. "Vapor barrier"
materials in the walls between garage and living space are also
beneficial.
Underground - The manual does not consider the impact of
underground garages since we found no adequate model for or data
on the infiltration of emissions. Only qualitative measures
to reduce infiltration through the garage ceiling and elevator
shafts are discussed. The primary impact should be from the
vent exhaust as an outside generator. A number of design variables
makes this a complex relationship that warrants further work.
Future Research
Validation and quanitification of the findings on CO generation
in kitchens and garages deserve highest priority because relation-
ships have been demonstrated and the expected results should
be maximum for the dollars spent. Such research could determine
the-effectiveness of various hood vent configurations, and of
connecting the oven to a flue. The research effort should include
23
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a thoroughgoing analysis of routes of pollutant travel from garage
to dwelling structure and of economical means for reducing such
movements.
24
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REFERENCES
1. Yocom, J. E., W. A. Cote, and W. L. Clink. Summary Report
of a Study of Indoor-Outdoor Air Pollution Relationships to
the National Air Pollution Control Administration. Contract
No. CPA-22-69-14. The Travelers Research Corp., Hartford,
Conn. 1969.
2. W. C. Eaton, Carl M. Shy, John F. Finklea, James N. Howard,
Robert M. Burton, George H. Ward, and Ferris B. Benson.
"Exposure to Indoor Nitrogen Dioxide from Gas Stoves".
Human Studies Laboratory, National Environmental Research
Center, Environmental Protection Agency, Research Triangle
Park, North Carolina. Revised January 1973.
3. Ferris B. Benson, John J. Henderson, J. E. Caldwell.
"Indoor-Outdoor Air Pollution Relationships: A Literature
Review". Environmental Protection Agency, National Environ-
mental Research Center, Research Triangle Park, North
Carolina. August 1972.
4. Lefcoe, N. M. and I. I. Inculet. Particulates in Domestic
Premises; I. Ambient Levels and Central Air Filtration.
Arch. Environ. Health. 22:230-238, February 1971.
5. Biersteker, K., et al. Indoor Air Pollution in Ratterdam
Homes, Int. J. Air Water Pollution, 1965.
25
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5 TRANSPORT AND DISPERSION OF AIR POLLUTANTS
The pollutants emitted at a source disperse in the surrounding
atmosphere in a manner that depends on the meteorological state
of the local atmosphere. The dispersion process and the disper-
sion equation used in this manual are reviewed briefly here.
References 1 and 2 provide a detailed presentation.
DISPERSION
1 2
Major Factors Affecting Dispersion '
Four parameters characterize the atmospheric dispersion
process:
1. Wind Speed - determines "ventilation" rate.
2. Wind Direction - determines path of direct
transport of pollutants.
3. Mixing Height - determines the depth of the
atmosphere available for vertical spread of
pollutants.
4. Atmospheric Stability - a measure of turbulence
in the atmosphere. A stability classification
method, based on wind speed and solar radiation
or cloud cover, proposed by Pasquill, is pre-
sented in Table 5.1.
27
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Table 5.1 KEY TO STABILITY CATEGORIES (AFTER TURNER)2
Surface Wind Day Night
Speed (at 10m) Inc°ming Solar Radiation Thinly Overcast
m sec'1 or 3/8
Strong Moderate Slight 4/8 Low Cloud Cloud
2
2-3
3-5
5-6
6
A
A-B
B
C
C
A-B
B
B-C
C-D
D
B
C
C
D
D
E
D
D
D
F
E
D
D
The neutral class, D, should be assumed for overcast conditions
durina dav or night.
Class A is the most unstable class/ and Class F the most
stable one.
High wind speed, unstable atmosphere, and "unlimited" mixing
height enhance the dispersion process and therefore are favorable
conditions for dispersal of pollutants. Low wind speed, stable
atmosphere, and limited mixing height lead to "buildup" of pollu-
tants in the atmosphere. An air pollution episode could occur
if these conditions prevail over several days in which significant
amounts of pollutants are emitted.
The topography of a region affects the air movement over
the surface, and hence affects the dispersion process.
Dispersion Equation
There are two basic approaches to mathematical description
of dispersion processes: 1) statistical modeling; and 2) model-
ing by conservation equations. Several variations of these two
28
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3 4
approaches are available. ' The steady-state Pasquill-Gifford
dispersion equation CGaussian distribution) is amenable to hand
calculations when only a few sources must be considered and
its precision is comparable to that of more sophisticated equations
Calculations presented in the manual are based on this equation.
The effluent from a stack normally continues upward movement
for a while before it begins downward motion. Stack parameters,
such as gas flow rate and temperature, and meteorological condi-
tions determine extent of plume rise. This amount of plume rise
determines the effective height of emission of pollutants, and
consequently affects the dispersion process. A method for esti-
mating plume rise is described later. When a source emits pollu-
tants near ground level, e.g. an automobile, the emission height
is usually taken as zero.
The ground-level concentration, C, at a point (X, Y, 0)
due to a continuous source with an effective emission height,
H, is given by the equation below.
exp
/ 2\
H |
I 2Qzj
exp
f 2\
2a2
I yy
\l2if G v2ir G
z y
C (X,Y,0;H) =
\l£-n O \l4Tf Q
C = concentration of a pollutant, usually expressed as (yg/m )
or (mg/m )
X, Y, Z = are coordinates of the point (receptor) at
which concentration is estimated, meter
H = effective emission height, meter
Q = source strength (pollutant emission rate), gm/second
IT = a constant, 3.14
29
-------
a and QZ = lateral and vertical dispersion coefficients,
meter. These depend on stability, surface
roughness, wind speed, and distance between
source and receptor, a and a increase with
distance between source^and receptor.
These also depend on concentration averaging
time; and their values are available for
averaging times of a few minutes.
u = mean wind speed, m/sec
This equation applies over a relatively smooth terrain.
Figure 5.1 illustrates a source-receptor system. The X-axis
is usually oriented along the direction of wind; and it is con-
venient to consider the source as the origin for the coordinate
system.
When the concentration is to be calculated along X-axis
(i.e., along the direction of wind, Y=O), the equation simplifies
to:
C (X,Q,0;H) = „ Q „
If the source discharges essentially at ground-level, then:
C (X,0,O:O) =
ay az U
Estimation of Plume Rise ' '
A number of equations are available for estimating plume
rise. It is difficult to choose among these formulas. Reference
8 provides detailed discussion of plume rise formulas. The
Briggs equations for neutral conditions (D stability) is used
in the manual for estimation of plume rise, AH:
AH = 1>6 pl/3 (3'5 x *}
30
-------
Figure 5.1 Coordinate system showing Gaussian distribu-
tions in the horizontal and vertical.
31
-------
where:
F = 3.14 Vf
T = ambient air temperature, °K
Ts = stack gas exit temperature, °K
u = average wind speed at stack level, m/sec
V^ = stack gas flow rate, m /sec
F - buoyancy flux parameter, m /sec
*
x =? distance at which atmospheric turbulence begins
to dominate entrainment, m
* 5/8
x = 14 F / For F less than 55
* 2/5
x = 34 F For F greater than or equal to 55
Figure 4-7 in the manual was prepared with this equation.
For a group of stacks, the average stack parameters are used
in calculating the plume rise. The effective height of emissions
is obtained by adding plume rise to physical stack height.
H = h + AH, meter
IDENTIFICATION OF WORST CASE CONDITIONS2'7'9
Temporal and spatial emission patterns, emission rates,
and the state of the atmosphere determine the level of pollution
at a site. As mentioned previously, an air pollution episode
could occur if conditions of low wind, stable atmosphere, and
limited mixing height prevail over several days. The manual
is not intended, however, for use in estimating concentrations
that could occur about 3 percent of the. time.
The concentration averaging time for a pollutant, specified
32
-------
in air quality standards, is based on health effects. In estimat-
ing worst-case concentrations for a pollutant, one must consider
temporal and spatial emission patterns, averaging time for the
pollutant, and meteorological conditions simultaneously. Because
particulate and SO2 have similar emission characteristics, they
are treated together in this analysis; CO is considered separately.
Carbon Monoxide (CO)
The major portion of CO is emitted essentially at ground
level by roadway vehicles and aircraft. For ground-level sources
(consider equation 5.3), higher concentrations occur with low wind
speed and stable atmosphere. The CO emission rate on a road is
usually highest during morning peak of traffic volume. The concen-
tration averaging time for CO is 1 hour, and during the morning
hours stable atmosphere could prevail. Consequently, stability
Class F, 1 m/sec wind speed, and morning peak hour are designated
as worst-case conditions for CO.
Particulate and
The major portion of these pollutants is emitted by elevated
stationary sources (e.g. power plants, space heaters) . For
elevated sources (consider equation 5.2), higher concentrations
over a time period of a few minutes occur with unstable atmospheric
conditions. However, as wind directions fluctuate widely during
unstable conditions, these concentrations also fluctuate consider-
ably. These high concentrations occur near the source (from
1 to 5 stack heights downwind) , and the concentrations decrease
rapidly downwind with increasing distance.
Under stable conditions, the maximum concentrations occurring
33
-------
for a time period of a few minutes are lower than those occurring
under unstable conditions. Concentrations averaged over a time
period of a few hours, however, could be higher during stable
conditions because of narrow flucuations in wind direction.
Further, these maximum concentrations occur at greater distances,
and consequently, significant concentrations could occur over
large areas.
Stable atmospheric conditions (classes E and F) occur during
evening and early morning, and during day time neutral stability
(class D) could prevail. Industrial activities, and hence particu-
late and S02 emission rates, are at their peak during the day.
The concentration averaging times for particulate and SO^ are
24 hours and 3 hours, respectively. Thus, in estimating concen-
trations, the temporal variations of emission rates and stability
should be weighted over the averaging time period. Variations
in emission rates are difficult to estimate. The combined con-
sideration of stability, emission rates, and concentration aver-
aging times led to selection of D stability as the worst-case
condition for particulate and S02.
For ground-level sources, the ground-level concentration
increases as the wind speed decreases. This is not so for elevated
sources over relatively short time periods. The plume rise is
inversely proportional to the wind speed, and the ground-level
concentration decreases exponentially as emission height increases.
Thus, maximum concentration occurs at some intermediate wind
speed. The combined consideration of average emission character-
istics and D stability led to selection of 4.5 m/sec wind speed
34
-------
as the worst-case wind speed for particulate and
For each given receptor and set of sources there is a unique
set of meteorological conditions that yield maximum concentrations
Generally, however, it is very difficult to determine the atmos-
sheric conditions of wind direction, wind speed, and stability
that will result in the maximum combined concentration from mul-
tiple sources. Thus, D stability and a wind speed of 4.5 m/sec
are general conditions likely to result in high concentrations.
SIGNIFICANT SOURCES
The pollutant concentration at a site due to a source depends
on: 1) rate of pollutant emissions; 2) location of the source
in relation to the site (source-receptor geometry); and 3) mete-
orological conditions.
The pollutant concentrations due to a ground-level source
decrease as the distance between the source and the site increases,
Pollutant concentrations from an elevated source pass through
a maximum before they start decreasing with distance. Thus,
a source located far from the site may have only marginal impact
on the site. Further, since pollutant travel time increases
with increasing distance from source to site, if emission rates
vary markedly and the concentration averaging time is short,
the source may become insignificant. The ambient air quality
standard (AAQS) is, of course, an important factor in determining
significance of a source. When the concentration at a site due
to a source is less than certain percentage (say, 5%) of the
standard, the source may be considered insignificant and need
not be accounted for in calculating total pollutant concentration
35
-------
at the site. To minimize the number of required calculations, the
manual gives criteria for identifying significant sources in each
source category. The methodologies for estimating emission rates
and concentrations are discussed separately under each source
category in the following section.
36
-------
REFERENCES
1. Air Pollution, Vol. I, Ed. Stern, A.C., 2nd Edition, Academic
Press, 1968.
2. Turner, D. B. Workbook of Atomspheric Dispersion Estimates.
U. S. Dept. HEW, PHS Pub. No. 999-AP-26, 1969.
3. Darling, E. M., Jr. Computer Modeling of Transportation
Generated Air Pollution. Report No. DOT-TSC-OST-72-20,
U. S. Dept. of Transportation, June 1972.
4. Rote, D. M. et al. Studies of the Argonne Integrated -
Puff Model. ANL/ES - 9, Argonne National Laboratory,
October 1971.
5. Carson, J. E. and H. Moses. "The Validity of Several Plume
Rise Formulas", J.Air Poll. Control Assoc., 19:862, 1969.
6. Briggs, G. A. Plume Rise. TID-25075, U. S., AEC, 1969.
7- Personal communication with Paul Morganstern, Walden Research,
Cambridge, Mass.
8. Stern, A.C. et al. Fundamentals of Air Pollution, Academic
Press, 1973.
9. Rote, D. M. and J. W. Gudenas. "A Steady State Dispersion
Model Suitable for Air Pollution Episodes", Paper presented
at 64th APCA meeting, June-July 1971.
37
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6 POLLUTANT EMISSIONS AND CONCENTRATIONS
This section describes development of techniques for estimat-
ing pollutant emissions and concentrations at the site resulting
from each major category of sources considered in the manual..
ROADWAYS
Emission Factors ' ' ' '
The emission rate of CO on a road depends on three major
factors*: 1) number of vehicles on a unit segment of the road;
2) types of vehicles; and 3) mode of operation of these vehicles -
starting, accelerating, decelerating, idling, or cruising at
steady speed. Vehicles of different size, type, and age emit
CO at different rates. Populations of these vehicles vary on
different types of roads in different areas. For simplification,
we used data on national vehicle population in developing weighted
average emission rates for different modes of operation. These
average emission rates are known as emission factors.
Because driving patterns (based on mode of operation) are
distinctly different on local roads (collector streets, arteries)
and on freeways, the manual provides emission factors for both
types of roadway.
* Data for estimating effects of ambient temperature are not
available.
+ The emission control device (if any) deteriorates with age,
leading to higher emissions.
39
-------
Local Roads
The driving cycle used by EPA in emission rate test procedures
(1975 Federal Test Procedure, FTP) is based on normal driving
patterns on local roads. Emission factors given in the manual
for local roads are based on this cycle. Although the driving
patterns on different local roads are similar, the average running
speeds and consequently emission factors, are different. Therefore,
speed correction factors are used for estimating emission rates
at different speeds. The average running speed for 1975 FTP
is 19.6 mph, and the emission rate of this test is used as a
reference.
Measurements of average traffic speed on a local road during
rush hour are usually not available. The posted limits on these
roads give some indication of average running speed. Following
are the speeds used in preparing Table 4.1 for application to
local roads:
Posted speed limit, mph 45 40 35 30, 25 15
Average peak-hour
running speed in 30 25 25 20 20 10
Table 4.1, mph
Emission factors for different years and different speeds
are calculated as follows:
Emission factor for _ 1975 FTP emission factor for that
a particular speed year x speed correction factor
The data are taken from Reference 1, which gives a detailed pre-
sentation. The 1975 FTP emission factors and speed correction
graph are in the Appendix.
40
-------
Freeways
On freeways, the car travels essentially at constant speed.
The speed, however, varies with traffic volume. The emission
ratio, presented in Reference 1 and defined below, was used in
calculating emission factors for different steady speeds.
Emission Ratio = Emission rate at the steady speed
1975 FTP emission rate
Because this ratio is essentially constant for different years,
only one emission ratio is given for each steady speed. The
emission ratios are tabulated in the Appendix.
Estimating Emission Density
The volume of peak-hour traffic on a road is usually available
from the local traffic authority- If this is not available,
the Annual Average of Daily Traffic (AADT) can be used to estimate
peak-hour traffic, which is about 8 to 15 percent of the AADT.
Chapter 3, Reference 6, gives details on estimation procedures.
Peak-hour traffic speed on a highway, if not available, can be
estimated by the procedure in the manual. Reference 6 describes
the method in detail.
When traffic volume and speed on a road are known, emissions
on the road, usually expressed as emission density, can be calcu-
lated as follows:
Q_ = K x V x E,
CO
where:
gm
Qco ~ C0 emission density, sec_m
V - peak hour traffic volume, vehicles per hour
41
-------
- emission factor, mile
K - conversion factor, calculated as below.
K = f hour . , ,mile> ,
^' > = 1.73 x 1(T7
Estimating Concentrations7 ' 8 ' 9 ' 10
The dispersion equation 5.1 can be used to estimate CO concen-
tration due to a road when the road is at grade-level and the
surrounding terrain is smooth. The elevation (or depression)
of a road affects the air movement pattern and, consequently,
the dispersion process.
Some experimental dispersion data for at-grade, elevated,
and depressed roads are given in Reference 8 . Because it is
difficult to account for all factors affecting dispersion in
an equation, we applied these data in preparing the manual.
Figure 4.3 in the manual is taken from Reference 8; and the
values are valid when the angle between the wind direction and
the road, 0, is greater than 22.5°. When 0 is less than 22.5°,
it should be considered to be equal to 22.5°. Further, values
in this figure apply only if the road is "infinitely" long.
No correction factors are introduced, however, to simplify cal-
culation procedures .
Calculating Total CO Concentration from Roads
The CO concentration at a site usually varies with wind
direction. Since identification of the wind direction that results
in maximum CO concentrations is often difficult, CO concentrations
at the site are calculated for eight wind directions to determine
maximum CO concentration. As it is difficult to estimate CO
42
-------
concentration when the angle between the road and the wind direc-
tion is less than 22,5°, only eight wind directions are considered,
Significant Roads
The standard used in the manual for CO is 15 mg/m . If
the worst-case CO concentration at the site due to emissions
on a road is less than 20 percent of that standard (i.e., 0.2
x 15 = 3 mg/m ), the road may be considered insignificant. The
significance criteria for local roads and freeways are discussed
below.
Local Roads
Because traffic volume on the feeder (residential) streets
is very low, these streets are not considered in calculating
total CO concentration at the site. For "collector streets",
the maximum traffic volume is estimated at 3000 vph. At 25 mph
traffic speed, the CO emission density is 2.5 x 10~ -3^— for
J sec-m
the year 1974. The distance at which the worst-case CO concentra-
tion due to this road falls below 3 mg/m is estimated to be
400 meters. The angle between the road and the wind direction
is taken to be 22.5°. Thus, collector streets within 400 m radius
of the site should be considered in calculating total CO concentra-
tion.
Freeways
Most freeways outside of a city are four-lane roads, and
near or within the city they become six-lane roads. The rush-
hour traffic volume on a six-lane freeway could be 12,000 vph.
At 45 mph traffic speed, the emission density on this freeway
-2
is 4.5 x 10 (gin/sec-meter) for the year 1974. The distance
43
-------
at which the CO concentration falls below 3 mg/m is estimated
to be 2000 meters. Thus, freeways within 2000 meters radius
of the site should be considered in calculating total CO concentra-
tion at the site. At 1 m/sec wind speed, the pollutant travel
time for this distance is more than half an hour. The concentra-
tion averaging time for CO is 1 hour, and the CO emissions on
a road drop considerably after rush hour. Consequently, the
maximum distance for significant freeways is limited to 1000
meters.
POINT SOURCES
Emission Rates
Emission rates for particulate and SO2 from point sources
are obtained from the National Emission Data System (NEDS) prepared
by the EPA.11
A single plant may have more than one stack emitting pollu-
tants. Each NEDS form is considered here to represent a stack
at the source. Ideally, each stack at the source should be evalu-
ated separately. To minimize calculations, however, stacks
that discharge pollutants at approximately equal effective heights
are grouped together. Stack parameters, such as stack height
and exit gas flow rate, and meteorological conditions determine
effective emission height. Selection of the parameters and
their ranges for grouping stacks is somewhat arbitrary; it is
a compromise between amount of computation and precision of results.
The emission rates are converted from tons per year to grams
per second by use of operating schedule data.
44
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Estimating Concentrations
The procedure for calculating effective emission heights
for elevated sources is described in Section 5.0, Estimation
of Plume Rise.
The ground-level concentration along the wind direction
(i.e, downwind concentration) due to a point source can then
be calculated by the equation :
C (X,0,0:H) =
"
exp
H
As values of dispersion coefficients are available for a time
period of a few minutes only, this concentration value is valid
for that time period. Because of meandering of wind, the downwind
concentrations become lower over longer averaging times . The
concentration averaging times for particulate and SO2 are 24
hours and 3 hours, respectively. Hence, it is necessary to adjust
the concentration that is calculated with the equation.
The relationship between longer and shorter averaging times
depends on a number of factors. ' A power law relation is
often used, but is not well established. For 24-hour periods,
the downwind concentrations were multiplied by 0.6; and for 3-
hour periods, the calculated value was used.
The ground level concentration at a point not along the
wind direction can be calculated from the equation:
C (X,Y,0:H) =
The expression exp
Q
0y az u
2 "
Y
L 2 °*2J
exp
is
2
Y
L 2oy2J
termed th
exp
e Coi
r H2
2a*2_
•rection Fa
ctor .
45
-------
As before, this concentration is valid for a time period
of a few minutes. But, unlike the downwind concentration, this
concentration is greater for longer averaging times because of
meandering of wind. No definite relationship is established
for calculating concentrations over longer averaging times.
So, concentrations for longer averaging times were calculated
by adjusting the correction factor to a higher value. The lateral
coefficient a increases as the atmosphere becomes less stable.
A 3-hour concentration for SO2 is taken to be the same as the
concentration for a period of a few minutes; the correction factors
were calculated by using o for D stability. For particulate,
correction facotrs were calculated by using a for C stability.
The dispersion coefficients used in the manual are taken
from Reference 7, and are valid for rural or suburban areas when
the terrain is smooth.
Total Pollutant Concentration Due to Point Sources
When the proposed site is affected by a number of point
sources, identification of wind direction that will result in
maximum particulate and SO,, concentration is often difficult.
The ground-level concentration due to point source decreases
rapidly as lateral distance from the wind direction increases.
The procedure used for calculating maximum CO concentration there-
fore is not suitable here. In the manual, then, concentrations
are calculated for four source-to-receptor wind directions associ-
ated with the four major point sources. One of these wind direc-
tions could be expected to give the maximum likely concentration.
The procedure is the same for calculating particulate and S02
46
-------
concentrations.
Significant Point Sources
The air quality standard given in the manual for particulate
is 210 yg/m for 24-hour averaging time; for SO2 it is 450 yg/ra
for 3-hour averaging time. If the pollutant concentration due
to a point source is less than 10 percent of the standard, the
source may be considered insignificant. A downwind concentration
3
of 40 yg/m for a period of a few minutes was selected as the
criterion for determining significance of a source of particulate
or SO-. Since 24-hour particulate concentration is obtained
by multiplying short-term concentration by 0.6, 40 yg/m is about
11 percent of the air quality standard for particulate. The
3-hour SC>2 concentration is taken to be the same as the concentra-
tion for a period of a few minutes; thus, 40 mg/m is about 9
percent of the standard for SO- •
In preparing the plot of distance versus source strength
(Figure 4.5 in the manual), we designated the effective emission
height as 10 meters, then obtained the normalized concentration
(C/Q) for different distances and calculated source strength
Q for concentration C = 40 yg/m .
SPACE HEATING
Introduction
A precise analysis of pollution loads due to space heating
would involve an inventory of the spaces heated in every enclosed
structure in a prescribed area surrounding the potential site,
together with knowledge of the fuel used to heat each structure,
the unit heat load required for each space (which would vary
47
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with structure and insulation), and the efficiency and condition
of each space-heating unit. These data, coupled with a valid
dispersion model for the worst-case condition, would yield the
optimum result we can presently conceive.
The major pollutants from space-heating emissions are particu-
late and SO2. Point sources, however, usually, contribute more
than 75 percent of these pollutant concentrations at a site. Of the
remaining 25 percent, emissions from area sources in the immediate
vicinity of the site contribute most of the pollutant (due to
area sources) at the site. Since proximity is significant,
we designated a square with a 1-kilometer side, centered on the
wind direction vector associated with maximum pollutant concentra-
tion from point sources, to represent the area sources. Refer-
ence 15 gives a detailed presentation.
The procedure presented in the manual falls far short of
the ideal, chiefly because of the overwhelming cost of collecting
the data needed to provide precise, quantitative values. The
only method now available for collecting the needed data would
be a door-to-door survey of a 2 kilometer-diameter area around the
site. Recognizing that the manual-user must do an analysis with
currently available data, we devised a patchwork procedure based
on a number of information sources and involving a number of
generalizing assumptions. The following section outlines the
procedure for analyzing the impact of space-heating sources.
Estimating Emissions
Values for the amount of residential heated space are based
48
-------
on data from aerial photographs and "Census Tracts", augmented
with data from field interviews or building permits, or both.
A pro-rata apportionment is made for tracts partially included
in the area influencing the site. A representative floor area
was selected for each size dwelling in the census tract data.
Data on commercial, industrial and institutional space heating
are much harder to acquire. We suggest a combination of references
to city directories and state "directories of manufacturers",
and interviews in the field as the basic data sources.
The percentages of residences heating with each fuel type
are tabulated for cities over 10,000, counties, and SMSA's in
the Census Bureau's "Detailed Housing Characteristics". These
percentages were applied to all building types and uses, multiply-
ing the percentage value by total floor area.
Data on average coal and oil usage were taken from Reference
11, and emission data were taken from Reference 2. These data
are tabulated below.
Fuel
Amount
(dwelling) (Degree-day)
Pollutant Emissions
Particulate
S02
Coal
0.0012 ton
20 Ib/ton
57 Ib/ton
Fuel
0.18 gallon
10 lb/103gal
43.2 lb/103 gal
We -selected an area of 10 square meters for estimating
emission density. Using 1250 square feet as the average floor
49
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area per dwelling unit, we expressed the emission data as follows:
Pollutant
gms x 10 Coal oil
Tsec-m2) (degree) 103 sq. ft.
Particulate 10.1 0.8
Sulfur dioxide (S02) 28.7 3.3
Estimating Concentrations14 ' 15 ' 16
Space heating emission sources are too numerous to be treated
individually. Particulate and SO- concentrations due to space
heating emissions could be calculated by (1) representing the
source with a single virtual point source, or by (2) considering
the emissions to be uniformly distributed over the area. The
second approach gives better results and is commonly used. Several
methods based on this approach are available for estimating pollu-
tant concentrations.
The method proposed by Hanna-Gifford is simple and gives
results comparable to those obtained with more complex methods.
References 15 and 16 provide detailed information.
The pollutant concentration C is given by:
C = K
U
where :
C - pollutant concentration,
gm
Q - emission density Second.m2—
U - wind speed , m/sec
K - function of stability, source distribution, and
pollutant
50
-------
Although this model is generally used to calculate annual
mean concentrations of a pollutant, it is also suitable for calcu-
lating short-term averages. The values of K, suggested by Hanna-
Gifford, are 225 for particulate and 50 for SO2. Figure 4.11
in the manual is based on these values of K.
Findings and Conclusions
If it were not that emissions from space heating are usually
minor in relation to emissions from industries and motor vehicles,
the procedure just outlined would probably be judged to entail
too great a potential margin of error. We include it in the
manual because it is the only method by which one can deal with
space-heating emission sources, short of the grossly expensive
door-to-door canvass method.
Re c omme n da t i o n s
The procedure outlined could be made less cumbersome and
more accurate if the Bureau of the Census could gather and print
data by urban block giving number of rooms per dwelling and heating
fuel used, and also publish values for heated floor areas and
fuel types used in industrial and business establishments at
the tract level in the "Census of Business". The analysis could
be strengthened also if local building inspection departments
could provide data tabulated by street address or by coordinates.
Instituting these measures would increase both the ease and the
accuracy of the space-heating analysis. As it stands, the proce-
dure is one of the weakest in the manual.
51
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PARKING LOTS
18 19
Estimating Emissions '
The magnitude of CO emissions on a parking lot depends on
the number of cars operating on the lot at the given time and
the average time (termed "residence time") a car operates on
the parking lot. Residence time is a function of size of the
parking lot, the number of gates, and traffic on the adjacent
streets.. For the manual, the average residence time is taken
to be 1.2 minutes.
Mode of operation of vehicles on a parking lot varies from
idle to about 15 mph. Since emissions from a car at low speed
do not differ significantly from those at idle, we calculated
emission density on the parking lot on the basis of a car at
idle. Individual parking areas range from 150 to 300 square
feet; an average is 200 square feet. For calculating maximum
emission density on a parking lot, we assumed that 70 percent
of the cars are started in the morning rush-hour period. Emission
density, Q, can be calculated as follows:
Q • sfoo x T x E x tnnc x °-70
where:
N - number of parking spaces
T - average residence time, minute
E - emission factor, 251s.
mm
A - average area per parking space, square meter
52
-------
As the parking lot is assumed to become 70 percent empty
in a fixed time period (1 hour) , the maximum emission density
Q is independent of parking lot size. The emission factor E
varies with years; a reference value of 15 25L_ is used in the
mm
calculation of Q below.
1.2 (min) x 15 gms x 10.8 (sg. ft/m2)
g 3600 (sec ) min 200 (sq. ft )
-4 gm
2.7 x 10 - o
Estimating Concentrations ' '
CO concentrations at the site due to parking lots depend
on the distance from the lot to the site, geometry of the lot,
and meteorological conditions . The worst-ease meteorological
conditions for CO are F stability and 1 m/sec wind speed.
Emissions on the parking lot may be considered to be
occuring at some point on the parking lot, and the CO concentra-
tion can then be calculated by use of the dispersion equation.
Alternatively, the parking lot may be divided into a number of
small elements, and each element treated as a point source. If
the parking lot is assumed to be of "infinite" length in direc-
tions perpendicular to the wind direction, the lateral component of
dispersion equation can be taken as unity (1.0) . The parking lot
can then be divided into inf initesimally narrow strips , oriented
perpendicularly to the wind direction, and the concentration can
then be calculated by integrating the dispersion equation over the
depth of parking lot. To simplify calculation procedures, we used
53
-------
this approach in the manual. The integrated form of the disper-
sion equation is presented below.
"a.
C(X 0 0-H) - 2Q 1 [1 H2
C(X,0,0,H) - __ -^ | -^ exp (_ ^^ dx
*,
Q - the emission density is assumed to be constant over the
parking lot.
Figure 4.4 in the manual is based on this equation.
Dispersion coefficients az were taken from Reference 7, and
H is assumed to be 2 m to account for initial dispersion in the
parking lot.
AIRPORTS
CO emissions associated with a commercial airport may be
grouped into two categories: (1) emissions from aircraft and
ground-service vehicles at the airport; and (2) emissions from
access vehicles in the area surrounding the airport.
The major portion of CO comes from aircraft operations,
and the relative strengths of the sources depend on the nature
of the airport; for example, an airport with a large number of
transfer passengers may have relatively small access-traffic
volume. CO emissions from access vehicles could be as much as
50 percent of aircraft emissions; CO emissions from ground-service
vehicles could be as much as 25 percent of aircraft emissions.
In evaluating the CO impact of an airport, the spatial and temporal
CO emission patterns should be considered.
CO emissions due to access and ground-service vehicles occur
over a large area at and around the airport, and it is difficult
to estimate the impact without details of airport operation and
54
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without use of a computer. As a conservative approach one could
assume that all CO emissions from aircraft occur over the runway.
The runway could then be treated as a road, and the distance
from the runway at which CO concentrations fall below a certain
level could be calculated. Beyond this distance the airport
does not have significant impact.
Emissions from an aircraft depend on the number of engines
and the type of aircraft. Emissions at the airport are a function
of the number of landing and take-off operations (LTO) of these
aircraft. Listed below are some average distributions of aircraft
types and LTO's.
18
Distribution of operations at major commercial airports
Percent of LTO at airport
Long-range jet 38
Medium-range jet 49
Turboprop 13
The weighted average CO emission for this distribution was
2
calculated to be 41.52 kilogram/LTO . Note that these are average
data; actual values vary widely among airports.
Peak-hour aircraft traffic usually occurs in the morning
and constitutes about 10 percent of daily LTO. A runway could
handle a -maximum of 60 landing or take-off operations an hour.
The average active runway length is about 1600 meters/ and the
emissions from aircraft occur at about 6 meters above ground.
The worst-case meteorological conditions for CO in morning hours
are F stability and 1 m/sec wind speed. CO concentration of
4 mg/m may be considered a low concentration for assessing
55
-------
impact of airports. Assuming this value, we then calculated
the distance at which the CO concentration due to a runway, with
wind direction perpendicular to the runway, falls below 4 mg/m3.
Yearly LTO Minimum distance between
the outer boundary of the
airport and the site at
which airport has insigni-
ficant impact, kilometer
Less than 36500 1.0
Less than 54750 1.5
73000 or more 3.0
Beyond 3 kilometer distance, the travel time for a pollutant
at 1 m/sec wind speed is more than 1 hour. Thus, beyond 3 kilo-
meter distance the airport does not have significant CO impact
for 1 hour averaging time.
RECOMMENDED IMPROVEMENTS TO POINT SOURCE CALCULATION PROCEDURE
The calculation of point source emissions by the present
Manual procedure is by far the most involved and time-consuming
procedure presented. Simplier procedures were considered, such
as developing industrial pollution indices for each Standard
Industrial Classification (SIC) codes, as presented by Epstein,
? o
et al. However, in metropolitan areas most of the particulate
and SO- pollution can be attributed to stationary sources. To
develop any confidence in the emission rates from the point source
emitters, the best available data should be employed. The effects
of different pollution control equipment can result in orders-of-
56
-------
magnitude differences in emission rates. At precent the only
up-to-date point source emission data readily available on a
national basis are from the EPA National Emission Data System
(NEDS).
Although they present all the necessary information on point
sources, the NEDS forms were not developed for general use.
Acquiring the needed data to follow the procedure presented in
the Manual may present difficulties in certain cases. Zimmer
and Armentrout found that state agencies had little experience
with NEDS reports and were not familiar with the other available
NEDS output formats. Of particular interest to this project is
the available report titled "Plant Emission Summary". This sum-
mary lists the total pollutant emissions from all sources within a
facility and could be used for the Point Source Significance
Test. Use of the totalled emission data would eliminate the
summing of all emission points within a facility. For larger
facilities with more than 100 emission points, the calculation
procedure can be a very tedious task. Thus, as a minimum step
it is recommended that local air pollution agencies or HUD A-95
offices maintain complete files of NEDS forms and emission sum-
maries for their region, updated semi-annually.
The procedure in the Manual for grouping stacks and deter-
mining effective stack height, resulting downwind concentration,
and pollutant impact from different wind directions is a lengthy
one. If many point sources are involved, each containing mul-
tiple emission points, this procedure becomes very lengthy. The
problem is compounded in calculations for medium and large low-
57
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density developments, since multiple cases must be run to evalu-
ate the impacts at different sight locations.
It is recommended that a computer program be developed to
handle NEDS data to allow the user to feed in site location(s)
and receive a printout of total pollutant concentrations. This
would eliminate the entire point source calculation procedure
in the Manual and allow the user to obtain values for cases by
simply submitting the locational coordinates of each site posi-
tion of interest.
Because the NEDS was developed primarily as an enforcement
tool for surveillance of stationary sources, such a computer
program is not planned. It could, however, be applied in assess-
ing the feasibility not only of residential developments but of
proposed industrial developments. Wider use of NEDS forms and
data would then justify the maintenance of an updated data file.
A computer model would be similar to the procedure used in
the Manual. The overall logic flow is shown in Figure 6-1.
Advantages of the computer system over the Manual procedure other
than ease of use are:
1. The significance test can be developed with lower
cut-off limits to consider more sources.
2. The emission point data need not be grouped, and
estimation of plume rise is thus more accurate.
3. Actual meteorological data can be used to allow
calculation of the worst case, not to be exceeded
more than once per year. The Manual simplifies
by considering the worst 3% level and a wind speed
of 4.5 m/sec.
58
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Input:
Site Locational
Coordinates
NEDS
Emission
Data
Significance
Test
Input:
Meteorological
Data
Significant
Sources
Pollutant
Dispersion
Model
i
Downwind
Pollutant
Concentration
Determine
Worst Wind
Direction
Highest
Pollution
Impact
Figure 6-1 Computerized point source model
59
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4. The wind direction resulting in the highest pollution
level can be determined with greater accuracy.
The method used in the Manual considered only wind
directions corresponding to vectors drawn between
the major point sources and the site. A simple
iterative technique can be used to determine the
worst-case wind direction.
For such a computer program to be functional it should be
available on a local basis, perferably at HUD A-95 offices. The
turn-around time required for use of a central federal facility
computer would likely be prohibitive for local planning applica-
tions .
60
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REFERENCES
1. Cirillo, R.R. and T.D. Wolsko. Handbook of Air Pollutant
Emissions From Transportation Systems, Argonne National
Laboratory, ANL/ES-28, December 1973.
2. Compilation of Air Pollutant Emission Factors, Second Edition
U.S. EPA/ AP-42, April 1973.
3. A Study of Emissions from Light Duty Vehicles in Six Cities/
U.S. EPA, APTD-1497, March 1973.
4. Kircher, D. S. and D. P. Armstrong. An Interim Report on
Motor Vehicle Emission Estimation/ U.S. EPA, Pub. No. EPA-
450/2-73-003/ October 1973.
5. Unpublished data provided by G. W. Taylor/ Mobile Sources
Division, Environmental Protection Service, Ottawa, Ont.
K1AOH3, Canada.
6. Highway Procedures Workbook, Report 133, Dept. of Transpor-
tation, 1971.
7. Turner, D. B. Workbook of Atmospheric Dispersion Estimates.
U.S. Dep. HEW, PHS Pub. No. 999-AP-26, 1969.
8. Air Quality Manual, Vol. 5, Appendix to Vol. 5, Federal
Highway Administration, Office of Research, Washington, D.C.
20590, April 1972. Available from NTIS, Report No. FHWA-
RD-72-37.
9. Sklarew, R. C., Modeling Transportation Impact on Air Quality,
EPA, National Environmental Research Center, Div. of Meteo-
rology, Research Triangle Park, N.C. 27711.
10. Johnson, W. B. "An Urban Diffusion Simulation Model for
Carbon Monoxide", J.A.P.C.A., 23_:490, June 1973.
11. Guide for Compiling a Comprehensive Emission Inventory, U.S.
EPA,. APTD-1135, June 1972.
12. Singer, I. A. "The Relationship Between Peak and Mean Con-
centrations", J.A.P.C.A., 13^:336, July 1961.
13. Montgomery, T. L. et al./ The Relationship Between Peak and
Mean SO^ Concentrations. Tennessee Valley Authority/ Muscle
Shoals, Alabama.
14. Clark, J. F. "A Simple Diffusion Model for Calculating Point
Concentrations from Multiple Sources", J.A.P.C.A., 14;347,
September 1964.
61
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15. Hanna, S.R. "A Simple Method of Calculating Dispersion from
Urban Area Sources", J.A.P.C.A., 2_1:774, December, 1971.
16. User's Guide for the Climatological Dispersion Model. EPA,
National Environmental Research Center,- Office of Research
and Monitoring, Research Triangle Park, N.C. 27711, EPA-
R4-73-024, June 1973.
17. Norco, J. E. et al., An Air Pollution Impact Methodology for
Airports - Phase I, U.S. EPA, APTD-1470, January 1973.
18. Geomet, Inc. Vehicle Behavior in and Around Complex Sources
and Related Complex Source Characteristics-Sub-Task-2-
Airports, EPA, Research Triangle Park, N.C. 27711.
19. Ibid-Sub-Task-4-Parking Facilities.
20. U'.S. EPA, Federal Register, 121:0329, Appendix 0, 1973.
21. Personal communication with Edwind L. Meyer, Jr., Environ-
mental Protection Agency, Office of Air Quality Planning
and Standards, Research Triangle Park, N.C. 27711.
22. Epstein, A.H., Leary, C.A., McCandless, S.T. A Guide for
Considering Air Quality in Urban Planning, EPA-450/3-74-020
23. Zimmer, C.E., Armentrout, D., Establishment of a Non-EPA
User System for State Implementation Plans, EPA Contract
No. 68-02-1001, Task 4.
62
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7 ANALYSIS FOR SITE DESIGN
Analysis for site design entails a set of calculations
and procedures required to optimize the choice of alternative
site layouts for the various elements of design, such as
buildings, landscaping, parking areas, and outdoor recre-
ation. At the beginning of the study our goal was to
quantify and formulate the variables involved with trans-
porting, mixing, concentrating, or stagnating polluted air
on or across a site and to use the resulting formulae to
develop rational design procedures. We were greatly dis-
appointed with the results achievable at this time; quan-
titative data are scarce and the problem is complex.
RESEARCH
The data search was particularly frustrating because
much research has been done in this area, and many opinions
stated, however subjectively, as to the air pollution con-
trol benefits of various configurations; yet almost none of
this work is quantifiably reducible to general rules.
We discovered little in the way of conclusive new data
in this area since the excellent review by Rydell and Schwarz
in 1968 , with a few exceptions that will be noted. We
63
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document here those design practices for which there is a
preponderance of reinforcing opinion, regardless of the
degree of precision provided by presently available data.
Effects of Building Shape and Arrangement
Almost all the deductions concerning these effects are
"rules of thumb." Having investigated in depth, we believe
that these relationships are much too complex to be con-
densed into a simple series of graphs to be readily manip-
ulated, by the mathematically unskilled.
a. Urban "canyons" created by long, smooth-faced building
walls set in parallel rows have the capacity to greatly
2 3
increase the velocity of windflows along the faces. '
"Streets, like buildings, alter microvlinate by
changing topography and creating new land shapes.
Canyon-like rows of tall buildings along narrow streets
create a funnel effect, frequently doubling the wind
speed, or, if the wind enters at a 45-degree angle,
accelerating the velocity on the windward side and
creating slower currents on the leeward."2
b. Wind eddies should be considered in site design, since
they can concentrate pollutants in the eddy areas.
"The orientation of a building with respect to
winds also has an important influence on the impact of
air pollution. Various building configurations with
respect to winds create different sized eddies around
the structure. An eddy, which is a slowly revolving
stationary mass of air, can trap pollution, increasing
its concentration many times. The larger the eddies
around a building, the smaller the volume of the wind
that passes by the building to sweep the pollutants
away."4 "As the pitch of the roof, the thinness, and
the height and width of a building or a building block
increases, the size of the eddies around the building
increases. A row of uneven roofs creating rough sur-
faces can slow the wind, holding pollution in the area
lonqer.
-------
c. Arrangement of Structures. Arrangement of structures
in such a manner as to block through movements of
prevailing winds tends to trap, pool, and eddy air.
Therefore, long linear blocks of structures without
breaks should be avoided if at all possible.
"Not only is the impact of air pollution on a
building affected by how the building changes winds and
eddies, but by the kind of climate the edifice itself
creates. Placed on a slope, a building or mining
debris can act like'an artifical hill, creating a new
slope climate.""
*
"The building can block cold air from spreading
downhill, holding the air stagnant to gather increasing
concentrations of pollution. In some southern cli-
mates, houses on stilts allow hot ground air to "roll"
under rather than through the buildings, avoiding the
heat and any pollution carried in the wind."l
Effects of Site Grading
a. Sumps. Site grading that creates low sump areas should
be avoided. During cold weather, these sumps collect a
stratified body of air in which pollutants are trapped.
As stated before, a building "courtyard" can also act
as an artifical sump.
"In the natural environment hills or uneven slopes
can block up pools of cool air. When streets or rail-
road beds are constructed that cut through these cold
air dams, they may create cold air floods. If pol-
lution is involved, air drainage may have serious
consequences for the health of people in the valley. A
new highway can also create a new alley for cold air
and pollution to settle in. Anyone who drives knows of
the efficiency of open-cut highways for trapping auto-
mobile exhausts. This principle also works in reverse:
where there was once free drainage a railroad embank-
ment or an artifically level highway can dam up pools
of cold air and highly concentrated pollution."^
b. Road Grading. The General Electric studies in New
York pointed up the fact that a road at the grade of
65
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the surrounding topography, or somewhat higher,
allows better dissipation of traffic pollutants
than does a road in a cut.
Setbacks
As a general rule, pollutant concentrations decrease
with distance from a high-traffic street or intersection.
There are enough disturbing anomalies in data, however,
(probably due to turbulence and eddying) that dependable
general relationships are not yet possible.
"Traditionally, planners have used open spaces as
a major tool to improve the quality of life in the
city. Today, we have even more reason to use this
technique because open space, especially planted open
space is not only aesthetically desirable, but acts to
diminish the impact of air pollution in several ways.
Greenery absorbs moisture and cools by evapo-
ration, creating a cooler, more humid climate than
stone and exposed soil. Temperatures over grassy
surfaces on sunny summer days are 10 to 14 degrees
cooler than over exposed soil, and there can be as much
as 1500 BTU per square foot less heat per season over
grassy surfaces."®
The buffer areas, which can be related to prevailing
winds, provide an opportunity for pollutants to be diluted
9
or dispersed. Hilberseimer considers this subject in
detail. Others have studied wind and temperature changes
over green areas compared with built-up urban areas, the
implication being that planted strips may aid in generating
air currents that will carry away pollutants.
Landscaping
Small-scale landscaping has shown no significant effect
in reduction of pollutants in the air; it does tend to
66
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increase air turbulence increases mixing, which results in a
lower net pollutant concentration at a given downwind point.
Kalyuzhnyi et. al. found that concentrations of pol-
lutants decreased by about half with 500 meters of open
space, and by two-thirds to five-sixths with 500 meters of
planted land. He suggestes strips of green space to aid in
wind formation to carry pollution away. He measured a 75
percent reduction in dust particle count over a 600-foot-
wide strip in Leipzig. Wainwright and Wilson , however,
found over a London park that the decrease in concentration
of sulfur dioxide with distance in the direction of the wind
was not related to wind speed but instead correlated closely
with variation of temperatures with height above the ground.
Parking
Large masses of parking space should, if possible, be
avoided in favor of a more dispersed parking scheme. Such a
scheme tends to reduce the peak pollution load on any given
structure by simple disperson, although it also tends to
increase the average exposure throughout the development.
Setbacks of buildings from parking should prove beneficial.
CONCLUSION
The only contribution this study and the resultant
manual can make to present residential design practice is to
make the planner aware, in very general terms, of those
variables he can manipulate that are likely to decrease
pollution levels at a given site. The only present-day
67
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alternative to this approach is for the planner to schedule
a series of scale-model wind tunnel tests for his project.
The implications for future research are clear, since we now
have no reliable quantitative relationships on which to base
onsite or near-site analysis for residential planning.
68
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REFERENCES
1. Rydell, C. Peter, and Gretchen Schwartz. "Air Pollution
and Urban Forms: A Review of Current Literature,"
Journal of the American Institute of Planners, Vol. 34,
No. 2 (March 1968).
2. Graham, W.E. "The ^Influence of Microclimate on Plan-
ning," Planning Outlook, Spring 1949
3. Landsberg, H.E. "Microclimatology, "Architectural
Forum," Vol. LXXXVI, March 1947.
4. Kuhn, Eric, "Air Flow Around Buildings," Architectural
Forum, Vol. 107, September 1967-
5. Kuhn, Eric. "Planning the City's Climate," Landscape,
Vol. 8, Spring 1961.
6. Lawrence, E.N. "Microclimatology and Town Planning,"
Weather, Vol. 9, August 1954.
7. Final Report on Study of Air Pollution Aspects of
Various Roadway Configurations. Submitted to New York
City Department of Air Resources. By The General
Electric Company, Philadelphia, Pennsylvania. September
1, 1971.
8. Olgyay, Victor. Design with Climate - Bioclimatic
Approach to Architectural Regionalism, Princeton, N.J.:
Princeton University Press, 1963.
9. Hilberseimer, L. The New City. Chicago: Paul Theobold,
1944.
10. Kalyuzhnyi, D.N., Kostovetskii, T.J., Devydov, S.A.,
Akselrod, M.B. Effectiveness of Sanitary Clearance
Zones Between Industrial Enterprizes and Residential
Quarters, Gigiena i Sanitariya, 1962, p. 9-12, Tranky
B. Levine.
11. Wainwright, C.W.K., Wilson, M.J.G. Atmospheric Pollution
in a London Park, Air and Water Pollution International
Journal, Vol. 6, 1962, pp. 337-347.
69
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8 INDOOR-OUTDOOR POLLUTANT RELATIONSHIPS
RESEARCH
Of great value in our search of available reference
material were the literature review by Benson, Henderson,
and Caldwell of EPA and certain materials provided by Mr.
Henderson. A comprehensive list of references is included
with this section.
One of the first attempts to model the inflow-outflow
parameters of buildings was presented by Holcombe and
2
Kalika , in a report sponsored by ASHRAE. This report
summarizes the effects of air-conditioning devices on intake
air pollutant concentrations, and more importantly develops
formulae expressing theoretical indoor-outdoor relationships
for a number of typical air conditioning systems under
steady-state conditions.
Also important to the methodology and theory developed
3 4
in our study were papers by Frederick H. Shair et al., '
not yet published at the time of our data search. Also
useful were several issues of the "Proceedings" of ASHRAE,
together with their publication "Handbook of Fundamentals."
FINDINGS
The findings of most of the earlier studies were dis-
appointingly inconclusive. Although measurements of indoor-
71
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outdoor concentrations of many pollutants have been taken at
a great number of locations, the usual result is a series of
concurrent readings, from which the reader must sort out
relationships or inferences. Sulfur dioxide is the only
commonly monitored pollutant for which reasonably consistent
data can be plotted on graphs of indoor-outdoor versus
789 "LO "LI
outside concentration ratios. '''
Many tests indicate the effectiveness of filters in
14 32
removing pollen and other particulates from the indoors.- '
A number of less general findings are listed below:
1. Gas cookstoves and attached garages contribute no-
12
ticable CO to the inside atmosphere.
2. Tobacco smoking is an important source of indoor
13
particulates.
3. Indoor fluctuations of pollutant concentration follow
outdoor fluctuations closely, with a time lag and
12
generally lower peaks.
4. No relationship has been established between building
types and indoor-outdoor pollutant ratios.
2
The Holcombe-Kalika report, though a great step
forward theoretically, does not show strong numerical
correlations in results of measurements at two Connecticut
office buildings, chiefly because of uncontrolled variables
and because the steady-state equations do not adequately
represent rapidly varying outdoor concentrations.
3 4
Shair et al. ' show good correlations between test
data and model equations in studies of buildings on the Cal
72
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Tech campus. Their equations were set up to respond rapidly
to fluctuations in outdoor pollutant levels.
THEORY AND MODELING
In the beginning stages of the study we made a number
of false starts in attempts to model indoor-outdoor pol-
lutant relationships on the basis of data then available.
First we tried to set up the indoor-outdoor ratio as the
dependent variable, with building-type categories as the
independent variable. We reasoned that the potential user
of the manual would be more familiar with building types
than with some of the more theoretical and mathematical
variables required for the more rigorous approach.
We soon found that the system of building type clas-
sification was inadequate to our needs, even with adap-
tation. The significant variables seemed to be building
volume and surface area, which vary widely within each
building category, and air circulation and filtration
characteristics, which do not directly relate to building
types. When this set of deficiencies became apparent, we
decided to set up a theoretical model based on the concept
of the building shell forming a system boundary for a closed
container with good internal mixing of constituent gases or
suspended matter.
The Holcombe-Kalika study provides good basic math-
ematics for use in steady-state conditions, but did not
respond to actual fluctuations in outdoor concentrations and
did not 'provide good enough correlations with actual test
73
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conditions. We therefore decided to proceed with a general
model that would respond to rapidly changing outdoor con-
ditions and indoor generation of pollutants.
METHODOLOGY FOR CALCULATING INDOOR POLLUTION CONCENTRATIONS
The model we constructed for predicting indoor air
pollutant concentrations makes use of data on permeability
factors for exterior walls of the structure, structural
dimensions and volume, characteristics of the air circu-
lation and filtration system, and internal generation. The
model is simply an accounting system for tracing the move-
ments of various air massed into, out of, and within a
dwelling unit over short increments of time.
Although the movement of air massed into and inside a
dwelling is continuous, we thought it well within the limits
of accuracy of available data to express the mathematics in
terms of net concentration changes occurrring within short
time segments. The mathematics thus could be simplified
into a format more easily manipulated and computer-programmed.
As data from continuously monitored indoor-outdoor environ-
ments are accumulated and a more, precise method is developed
to account for infiltration factors and rates, this model
could be revised to incorporate continuous-change-state
mathematics, if this is deemed desirable.
The general equation for the change in pollutant con-
centration in a dwelling space over a short period of time
can be expressed as follows:
74
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Definitions
C1 = Concentration in interior space in the beginning of
the incremental period.
C- = Concentration in the interior space at end of incremental
period.
C = Concentration in the exterior space adjacent to
exterior walls.
C = Concentration in garage adjacent to exterior wall
' (also in carport area adjacent to wall)
C = Concentrations within the units above and/or below the
v unit under evaluation. During the heating season,
vertical infiltration from thelower level could have a
significant effect; during cooling season, the
opposite could occur. This factor requires a good
deal more information.
C = Concentration at exterior air intake of a forced air
system.
Q = Generally, incremental quantity of influent or effluent
air in a given period.
Q , Q , Q , Q_ are quantities corresponding to the above C ,
V Cv' V
O - Quantity of air from dwelling space recirculated.
V B volume of dwelling unit or interior space in question.
g = Amount of interior generation during the incremental
period (grains)
R « An expression 'of the attenuation rate of reactive
pollutants on interior surfaces
e = Filtration efficiency, percent removal for single pass
e = efficiency of make-up air filter
• * efficiency of recirculation air filter
75
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Figure 8-1 illustrates the relationships involved.
Mixing Factors:
The formula assumes complete mixing between applications
of the formula, an assumption most nearly assured of being
correct in applications that involve a typical forced-air
system. If the quantity of recirculated air approaches or
exceeds the volume of the dwelling unit, mixing seems
virtually assured. The most obvious way to deal with the
unknown "mixing effect" is to "calibrate" the formula by
comparison with monitored data from buildings having known
infiltration, circulation, and volume parameters.
Testing the Indoor-Outdoor Pollution Model
New data from Cal Tech (Shair, et al.) are based on a
modified form of the formula we have set up. In tests of
their formula against monitored readings in various build-
ings on the Cal Tech campus, correlations were good.
We decided that the best available test of our form of
the formula would be to apply it to the same building con-
figurations reported in the Cal Tech study and to determine
correlations with the Cal Tech formula and with the moni-
tored readings. We therefore programmed the data and applied
the model to two configurations of the Dabney Hall location
at Cal Tech. The results correlate very well with data from
the Cal Tech formula and somewhat less well with the data
obtained in monitoring pollutant levels. In each case the
correlation is much stronger than the input data.
76
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FILTER
EXHAUST FAN
RECIRCULATED AIR
FILTER
EXHAUST AIR
BUILDIMG VOLUME V
INDOOR SOURCES g
SINKS R
Figure 8-1 Schematic representation of outdoor-indoor model.
-------
Our first run-through of the Dabney Hall data assumed
5-minute time increments between iterations of the formula.
We theorized that an even closer correlation with data from
the Cal Tech formula would be achieved by use of a shorter
time increment. Therefore we ran the data through again
using a 2-minute increment; the resulting values, however,
were virtually identical with those obtained with the 5-
minute increments. From this we can guess that (1) possibly
the. Cal Tech formula is slightly flawed by deletion of
certain small factors for mathematical convenience, or (2)
perhaps a very small time increment would be required to
match the integral formula. Since the correlation was
adequate for our purposes, we did not test the model further.
Computer Investigation of Cases
Having been validated with Shair's test results, the
model seemed sufficiently accurate for use in exploring the
impact of variables in building and mechanical design and
construction on interior air pollution. A variety of
prototype cases were analyzed by means of the computer.
Following is a short summary of the building types and
variables tested:
Building Types and Floor Areas
1. Single-Family Dwellings
2
A. 1000 ft single-story
2
B. 1600 ft single-story
C. 2000 ft2 two-story
78
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2. Low-Rise Apartments
A. Two-story single-load (or townhouse)
B. Three-story double-load (SDU/floor)
3. High-Rise Apartments
A. Single Long-corridor 10-story, 20 DU/floor
B. Double short-corridor, 12 DU/floor
C. Three-wing composite 30-story, 36 DU/floor
Heating/Cooling Systems
1. Hot-water or steam radiator
A. Closed-window
B. Open-window
2. Forced-air Systems
A. Unfiltered
B. Filtered
(1) Efficiency =0.2
(2) Efficiency =0.9
(3) Filter on return air only
(4) Filter make-up air only
(5) Filter on make-up and return air
Structural Permeability Variables
1. Modern "tight" building
2. Old "leaky" building
Source Variables
1. Interior generation
2. Infiltration from subterranean garage
3. Make-up air intake at a low-pollution location
4. Pollution reaction with walls, floors, ceilings
79
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5. Exterior levels were assumed to follow a prototypical
two-humped curve, with morning and afternoon peak
levels, as indicated in Figure 8-1. Also a constant
exterior level representing industrial TSP and S02
emissions was included as in input.
OPERATIONAL ASSUMPTIONS
Where data were sufficient to allow formulation of a
statistically correct (i.e., 97th percentile, etc.) para-
meter, we attempted to insert into the model a conservative
condition. The following section attempts to explain and
justify some of the assumptions made.
Outdoor Concentration Time Gradient
The simplified outdoor concentration profile shown in
Figure 8-2 was used to represent a typical time-concentration
relationship. The type of pollution sources and prevailing
meteorological conditions determine the shape of this curve.
This two-humped curve is, however typical for locations with
significant impact from roadways.
Wind Driving Pressure
Wind driving pressure equivalent to that generated by a
10 mph wind (0.05 in. of H2O) was selected as the maximum
that might be expected in conjunction with high-pollution
conditions. Statistically, this seems quite conservative,
but this factor was possibly overdone in order to compensate
for factors not considered in the model because of lack of
data, such as chimney effect. An equal vacuum was assumed
on the leeward side of the structure.
80
-------
40-r
30-
UJ
CJ
o
o
20
00
o
°- 10-
0
•
^
\
\
\
v
/
*
\
\
I
7 8 9 10
I
11
12 13
14 15 16
TIME-HOURS
17 18 19 20 21 22
Figure 8-2 Typical outdoor pollution profile.
-------
Effective Infiltration Area
We assumed that wind driving pressure acts equally on all
upwind walls. In other words, wall area available for infiltra-
tion was taken as half of the total wall surface, deducting door
and window areas, which were assumed to be in the same propor-
tion on the upwind and downwind sides.
We assumed that full wind pressure acted on the cooling of
the top story, with infiltration occurring over the upwind half
of the ceiling and exfiltration on the downwind half.
We assumed that floors have no significant infiltration
driving force exerted and assigned them a zero value. This
assumption is obviously valid for slab floors, and probably
not entirely valid for a structure with crawl space below
the floor. A basement structure has some small potential
for infiltration through small basement windows, but such a
value is not established by available data, and subjectively
it appears small.
Infiltration Rates
For walls we assumed that an infiltration rate of 0.5 ft /
2
hr/ft is representative of modern construction with vapor
barriers. Much lower values are observed in test sections,
but occasional poor workmanship can reduce sealing effec-
tiveness; therefore we considered 0.5 a reasonable value
that is obtainable with ordinary workmanship and inspection.
For older structures we assumed an infiltration rate of 5.0
82
-------
ft3/hr/ft2, very much a "ballpark" estimate. An old struc-
ture with exterior stucco and interior plaster in good
condition could duplicate the rates of modern structures.
In many older masonry structures, however, the infiltration
rates range much higher than 5.0. The choice was based
solely on a judgment of what values would be both conserv-
ative and representative.
For windows and doors, we assumed values of 14 ft /
hr/ft of sash or edge crack with weatherstripping and 140
ft /hr/ft without weatherstripping.
Single-Family Structures
The first structure selected for analysis was a 1600
square foot single-story building. We calculated surface
area from an assumed floor plan, computed length of windows
and door cracks, using the infiltration rates mentioned
earlier, computed total infiltration in ft /hr for both
"modern" and "old" structures. For other single-family
prototypes, the infiltration rate was assumed to vary
directly with surface area of the structure.
Multi-Family Structures
Multi-family prototpyes were selected from actual floor
plans. We measured interior volumes and exterior surfaces
directly and again took infiltration as proportional to the
outside surfaces. Because of the many complicating factors
and the absence of supporting data, we abandoned the attempt
to calculate infiltration for a single living unit in a
83
-------
structure. The calculations for multi-family structures
assume a uniform distribution of air pollutants throughout.
Interior Generation
All that we know definitely about indoor pollutant
generation are the general categories of sources and the
fact that in some structures with given circulation char-
acteristics these sources could increase localized pollutant
concentrations. Because present data are not adequate to
deal with localized variations, the factors for internal
generation assume good mixing throughout the dwelling. The
model is capable of handling any pattern of internal gen-
eration and any attenuation when valid values become avail-
able.
Data Format
The data resulting from each computer run for each
building prototype took the form of interior concentrations
at 5-minute intervals over the period of the run. For our
purposes, results were as good and much more convenient when
the computer continued the 5-minute iterations but printed
out readings only on the hour.
The indoor-outdoor ratio was computed by averaging
the peak readings for the applicable period of time for both
indoor and outdoor locations. For example, if an 8-hour
standard were under consideration, the averages of readings
for the highest 8-hour period in the day were computed for
both indoor and outdoor concentrations. These periods did
84
-------
not usually coincide because of the time lag required for
infiltration of pollutants to exert an effect on indoor
levels. We then divided the high indoor level by the high
outdoor level and plotted the result.
The indoor-outdoor ratios and periods selected for
inclusion in the manual were determined by the time periods
finally selected for the air quality standards. The total
range of ratios calculated and graphed, for the two-humped
curve characteristic of auto emissions, included ratios for
interval of 1, 3, 8, and 24 hours. For the uniform emission
rate characteristic of industrially generated SO and
particulates, the 3-hour and 24-hour ratios were calculated.
Modeling of SO2 was abandoned because of insufficient data
on internal attenuation by paint, fabrics, and other materials
We therefore deal with SO- very simplistically as a fixed
ratio.
RELATIONSHIPS
The key variables in indoor-outdoor pollutant levels
appear to be interior volume of the structure as related to
surface area. For any given set of conditions of air
circulation, permeability, filtration, and other parameters,
the plot of volume-to-surface-area ratio (V/SA) versus
pollutant reduction shows a consistent and significant
trend. It is possible therefore to deal with the design
problem in a graphical format. With this goal in mind, we
plotted the results of our studies with V/SA on the Y-axis
and the proportion of indoor to outdoor concentrations on
85
-------
the Y-axis.
Some cases modeled did not conform well to graphing on
this set of axes, at least not without interpretation. The
case in which concentration of a pollutant at a forced-air
system intake is significantly lower than at the exterior
walls generally, is dominated by the concentration of the
intake air. In most cases, the plot of V/SA versus inlet
pollution level exhibits the same ratio as the plot of V/SA
versus general outdoor pollution level, so the significant
and consistent indoor-outdoor comparison in this case is
indoor to inlet ratio.
Also, a large garage infiltration will throw an in-
consistency into the ratio, depending on a great number of
ill-defined variables. This situation was handled with
"tack-on" factors.
Generally, the effect of tighter building construction
and larger V/SA ratio is to slow infiltration of pollutants
from the outside. This evens out the peaks and valleys and,
therefore, is most successful with highly fluctuating exterior
concentration values. The reduction of infiltration is most
apparent in calculations that entail a pollutant standard
covering a shorter time period. For example, the 1-hour stan-
dard for carbon monoxide is highly responsive to building sealing;
the 24-hour standard for particulates responds hardly at all.
The effect of filtration devices or chemical removal
agents is less linked with time. An effective filtration
86
-------
device has as much effect on particulates with the 24-hour
standard as on CO with the 1-hour standard.
An open-window case was run to demonstrate that indoor
pollutant levels closely follow those outdoors when windows
are open. The model verified this supposition fully.
RECOMMENDATIONS
Because of time limitations on this project, we did not
process a number of somewhat less-typical cases that might
have exhibited some significant variation from our model. A
more significant weakness is that only two real test cases
(those with Dabney Hall data) were run to confirm the
accuracy of the model. A program of further testing should
be specifically aimed at verifying the model for a wider
range of structures, materials, and operating conditions.
A great body of knowledge still requires research to
fully validate the indoor-outdoor model for dependable
everyday use by a residential planner with limited technical
training. Investigation of the following factors could
significantly strengthen the work.
1. Permeability of modern building materials, including:
Taped plaster board
"Sandwich" construction panels
Plywood sheathing
Modern masonry and hollow-core block
Masonry veneer over stud walls
New vapor barrier materials, such as plastic and
aluminum or composites.
87
-------
2. Internal generation of pollutants:
Co from stoves and fireplaces
HC from tobacco smoking
Dust from vacuuming and other household cleaning.
3. Room-to-room variations in pollution levels.
4. Unit-to-unit air movements in multi-family configu-
rations .
5. Vertical permeability of high-rise structures, in-
.eluding more cause-and-effect modeling. Studies of the
"chimney effect."
6. Relative permeabilities of various gases. Is a "vapor"
barrier the best barrier against CO or SO2?
7. The graphical displays show clearly that any form of
reasonably effective filtration in a forced-air system
with typical recirculation rates is highly effective.
Even a 10 percent effective filter,- for instance, can
significantly reduce levels of some pollutants. This
finding suggests research into low-efficiency filters
for the gaseous pollutants.
8. Dependable exterior air-current analysis. How much
pollutant recirculates into the structure from its own
flue? What are the effects of eddying?
9. Effects of kitchen or bathroom fan vents.
10. Concentrations of pollutants in various garage struc-
tures.
11. Reaction rates of pollutants with building materials
and furnishings. This study would produce an alterna-
tive factor, which is required to develop a more quanti-
tative relationship for S02 infiltration.
88
-------
EXAMPLES OF BUILDING DESIGNS
Infiltration Rates - Single-Family Modern
Case I - 1-Story, 1600 S.F. floor area
12,800 ft3 interior volume
Wall Area = 1,312 ft2
- 197 Windows @15%
1,115 ft2 net walls
x 0.5
2
558 ft infiltration surface walls
800 ft2 roof
1,358 ft2 Total
x 0.5 ft3/hr/ft2 =
679 ft3 infiltration through walls
Windows - 4 - 3x5 double-hung
3x3= 9
2 x 5 = 10
5 x 19-95 L.F. window crack
1-3x7 Doors
20 x = 20 LF door crack
Total Leakage 115 LF crack length
x 14 CF/hr/LF
1,610 ft /hr windows, doors
679 ft3/hr walls
2,289
Round off to 2300
89
-------
Infiltration Rates - Single-Family "Leaky"
Case 2 - Single-story 1,600 SF floor area
12,800 ft interior volume
Wall Infiltration:
1,115
x 0.5
net walls
558 ft infiltration surface, walls
2
800 ft infiltration surface, ceilings
2
1,358 ft infiltration surface, Total
x 5 ft3/hr/ft2
6,790 ft /hr infilt. walls & ceilings
Windows & Doors
115 LF Crack Length (from Sht. 1)
x 140 ft3/hr/ft crack
16,100 ft through doors & windows
Total Infiltration
6,790 ft walls
16,100 windows & doors
22,890
90
-------
BUILDING PROTOTYPES SELECTED FOR MODELING
!• One Story, 1000 ft2 v = 8'000 Ft
Area Walls 1040
Roof 1000
2040
R = 3.92
2. One Story, 1600 S.F. V = 12,800
Area Walls 1300 ft2
Area Roof ±600 ft2
2900 ft2
R = 4.41
3. Two-Story, 2000 S.F.
24' x 42' exterior dims.
V = 2000 x 8' = 16000 ft3
A = 2112 Walls + 1000 Roof = 3112 Total
R = 5.14
4. Two Story Apartment, Single-load or Townhouse Rows of 8
A = 8800 x 2 = 17,600 ft2
V = 140,800 ft3
Area Walls = 6,880 ft2
Area Roof = 8,800 ft2
15,680 ft2
R = 8.98
91
-------
5. Three-Story Apartment, Double Load
V = 265,200 ft3
Area Walls = 11,280 ft2
Area Roof = 11,050 ft2
22,230 ft2
R = 11.99
6. Ten-Story Long-Corridor
Area/floor = 20,000 ft2
Volume = 20,000 x 10 x 10 = 2,000,000 ft3
Wall Area = 12,000 ft2 x 10 = 120,000
Roof 20,000
S.A. 140,000
R = 14.28
7. Twenty-Story High Rise (12 D.U./floor)
V = 64 x 145 x 20 x 10 = 1,856,000
Area Walls = 83,600
Area Roof = 9 , 280
92,880
R = 19.98
8. Thirty-Story Three-Wing Apartment
Area of one floor = 29,840 ft2
V = 29,840 x 30 = 8,952,000 ft3
Area Walls = 1,152 x 10 x 30 = 345,617 ft2
Area Roof = 29,840 ft2
S.A. = 375,487 ft2
R = 23.84
92
-------
REFERENCES
I. Benson, F.B., Henderson, J.J. and Caldwell, D.E. Indoor-
Outdoor Air Pollution Relationships: A Literature
Review, Environmental Protection Agency, August 1972.
2. Holcombe, J.K. and Kalika, P.W. The Effects of Air
Conditioning Components on Pollution in Intake Air,
ASHRAE Transactions 1971.
3. Shair, F.H., and Heitner, K.L. A Theoretical Model for
Relating Indoor Pollutant Concentrations to Those Out-
side, October 1973.
4. Hales, C.H., Rollinson, A.M., and Shair, F.H. Experi-
mental Verification of the Linear Combination Model for
Relating Indoor-Outdoor Pollutant Concentrations,
November 1973.
5. American Society of Heating, Ventilating and Air Con-
ditioning Engineers (ASHRAE). Proceedings.
6. American Society of Heating, Ventilating and Air Con-
ditioning Engineers (ASHRAE). Handbook of Fundamentals,
1971 Edition.
7. Phair, J.J. Shephard, R.J. Carey, C.G.R., and Thomson,
M.L. The Estimation of Gaseous Acid in Domestic
Premises, Brit, J. Ind. Med. (London). 15:283-292,
October 1958.
8. Biersteker, K., de Graaf, H., and Nass, Ch. A.G. Indoor
Air Pollution in Rotterdam Houses, Int. J. Air Water
Poll. 9:343-350, 1965.
9. Wilson, M.J.G. Indoor Air Pollution, Proc. Roy. Soc.,
Ser. A. (London). 300:215-222, 1968.
10. Weatherly, M.L. Air Pollution Inside the Home, Warren
Spring Laboratory INvestigation of Atmospheric Pollution,
Standing Conference of Cooperating Bodies, May 16, 1966.
11. Weatherly, M.L. In: Symposium on Plume Behavior,
Int. J. Air Water Poll. 10:404-409, 1966.
93
-------
12. Yocom, J.E. and Cote, W.A. Indoor/Outdoor Air Pollutant
Relationships for Air-Conditioned Buildings, American
Society of Heating, Refrigerating, and Air-Conditioning
Engineers, New York. Preprint of paper for inclusion
in ASHRAE Transactions, 1971.
13. Yocom, J.E., W.A. Cote, and W.L. Clink. Summary Report
of a Study of Indoor-Outdoor Air Pollution Relationships
to the National Air Pollution Control Administration.
Contract No. CPA-22-69-14. The Travelers Research Corp.
Hardford, Conn. 1969.
14. Cohen, Milton B., M.D. Further Observations on the Use
• of Filtered Air in the Diagnosis and Treatment of
Allergic Conditions.
15. Cohen, Milton B., M.D. Preliminary Report of the Treat-
ment of Hay Fever in Rooms Made Pollen Free by a New
Filter.
16. Gay, L.N., M.D. The Treatment of Hay Fever and Pollen
Asthma by Air-Conditioned Atmosphere.
17. Studies Concerning the Effects of Atmospheric Pollution
on the Indoor Environment and Measures to Prevent
Pollution by Air Filtering System Designing Committee.
18. Shozaburo Mshido. Air Conditions in Dwellings with
Special Reference to Numbers of Dust Particles and
Bacteria.
19. Ishido. Air Pollution in Osaka City and Inside of
Buildings.
20. Richardson, N.A. Evaluation of Filters from Removing
Irrtants from Polluted Air.
21. The Reduction of Smog Effects in California Institute
of Technology Campus Buildings.
22. Weatherly, M.L. Air Pollution Inside the Home.
23. Whitby, K.T. Size Distribution and Concentration of
Air-Borne Dust.
24. Whitby, K.T. The ASHRAE Air-Borne Dust Survey.
25. Kranz, Peter. Indoor Air Cleaning for Allergy Purposes.
26. Whitby, K.T. Field and Laboratory - Performance of
Air Cleaners.
94
-------
27. Criep, L., M.D. Air Cleaning as an Aid in the Treatment
of Hay Fever and Bronchial Asthma.
28. Rappaport, B.Z., M.D. Effect of Air Filtration in Hay
Fever and Pollen Asthma.*
29. Nelson, Tell, M.D. The Effect of Air Filtration in
in Hay Fever and Pollen Asthma.
30. Spiegelman, Jay, M.D. Annals of Allergy. Effects of an
Air Purifying Apparatus on Ragweed.
31. Spiegelman, Jay, M.D. The Effect of Central Air Filtration
and Air Conditioning on Pollen and Microbial Contamination.
32. Vaughan, W.T., M.D. Air Conditioning as a Means of
Removing Pollen and Other Particulate Matter and of
Relieving Pollinosis.
33. Bahnfleth, D.R., Moseley, T.D., and Harris, W.S., ASHRAE
Research Report No. 1614 - Measurement of Infiltration in
Two Residences, Part I - Technique and Measured In-
filtration. ASHRAE Transactions, Vol. 36, 1957, p. 439.
34. Sasaki, J.R. and Wilson, A.G. Air Leakage Values for
Residential Windows. ASHRAE Transactions, Vol. 71, Part
II, 1965, p. 81.
35. Larson, G.L., Nelson, D.W., and Braatz, C. ASHVE Research
Report No. 851. Air Infiltration Through Various Types
of Brick Wall Construction. ASHVE Transactions, Vol.
36, 1930, p. 90.
36. Larson, G.L., Nelson, D.W. and Braatz, C. ASHVE Research
Report No. 868. Air Infiltration Through Various Types
of Wood Frame Construction. ASHVE Transactions, Vol. 36,
1930, p. 397.
95
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9 CONCLUSIONS
SUMMARY OF RESULTS
The chief aim of this research effort was to produce an
evaluation method for general, nationwide use to help
minimize the effects of air pollutants on residential
environments. Results of this effort are now published in
the form of a manual and this more detailed technical
report, which together have some important auxiliary uses:
1. The manual/report presents a summary documentation of
the current state of the art in workable small-scale
diffusion modeling.
2. The manual/report sets up a number of relationships and
hypotheses that may be judged to warrant further
research.
Models are provided for the assessment of large point
sources and of area sources consisting of large parking
areas and the heating of residential, business, institu-
tional, and manufacturing spaces. A model is also given for
assessment of impacts on residential sites from nearby
traffic sources. Recommended design practices are outlined,
more generally than we originally intended. Although some
of these practices entail possible economic impacts, they
97
-------
are mostly compatible with other practices recognized as
good design procedures.
LIMITATIONS
The chief weakness of the manual is that many of the
relationships must be further validated experimentally to
ensure a reasonable degree of accuracy. Another shortcoming,
caused by time and budget constraints, is that the various
models do not handle a wider range of input conditions.
The manual is not as concise or as easy to use as was
originally envisioned. Nor is the precision of results
attainable as great as we had hoped. Accuracy was not fully
validated for all cases, especially the complicated high-density
case. In addition, the methodology cannot be applied to all
of the important pollutants because base data of sufficient
quality were not available.
A weakness related more to the entire context of
residential planning than to the manual is that the cost/
benefit ratios for the procedures developed in the manual
have not been weighed against those of alternative pro-
cedures. Subjectively, we feel that the best results could
be obtained by reducing the generation of pollutants rather
than by treatment of site design and building construction
to reduce their impact. Many of the procedures outlined are
stopgap methods, useful only until better regional models are
set up for larger metropolitan areas. This is especially true
with the assessment of impacts from point sources.
98
-------
We made no effort to develop a procedure for estimating
lifetime pollutant exposures because we think that a short-term
model is a more accurate indicator of human health effects than
a long-term model, which would he required to determine lifetime
exposures at a residential site.
We do not believe that use of the manual procedures would
cause any significant change in other facets of environmental
concern such as noise abatement, water pollution control, or
solid waste disposal, and therefore did not pursue that line of
investigation.
PRESENT USEFULNESS OF THE MANUAL
In spite of the weaknesses just mentioned, we believe that
the manual is usable and valid with residential construction
in this country. We cite the weaknesses of the manual only to
point out that a more concise, more usable, and more accurate
manual could be produced with, we feel, a small amount of addi-
tional research and testing.
RECOMMENDATIONS FOR FURTHER STUDY
Following are some of the projects recommended as further
efforts to improve the techniques of residential site evaluation.
1) A network for point source analysis that would enable
a local air pollution control agency to provide a maximum pollu-
tant level at any coordinate point resulting from all point
sources plotted with NEDS data.
2) Validation of the Shair et al. indoor-outdoor model
by testing of construction materials and mechanical equipment
and by documentation of the range of outdoor pollutant levels
99
-------
encountered in the U.S.
3) Research of indoor pollutant generators, particularly
fireplaces and gas appliances such as dryers and cookstoves.
4) Consultation with the Bureau of the Census concerning
possible publication of fuel source data by census tracts
or city blocks rather than in county-wide tabulations.
5) Longer-term and intensive analysis of air movements
near and on residential sites, such studies to encompass many
significant variables and provide dependable numerical data.
We believe that this research has had low priority because produc-
tion of usable data would require a great deal of work.
6) Experimental application of the evaluation models to
different housing site configurations and meteorological conditions
100
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APPENDIX
Table A-l gives automobile emission data referred in the Report
and used in the calculation procedures in the Manual. Table
A-2 lists model emission ratios for light-duty, gasoline-powered
vehicles. Figure A-l shows relationships of average route speed
and speed correction factors for three pollutants.
Table A-l 1975 FTP (HOT OPERATING) CO EMISSION FACTOR
BASED ON NATIONAL POPULATION VEHICLE MIX18
(LOW ALTITUDE AREAS)
Mid-Year
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1985
1990
CO Emission Factor
71.89
67.28
61.82
55.98
50.68
45.55
39.46
33.79
28.85
24.82
21.00
12.10
10.76
101
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TABLE A-2. Li^ht LXity Gasoline-powered Vehicle Modal Umission Ratios
18
Mode
r 11 t)
Idle
Steady State
Speed (mph)
15
30
45
60
Acceleration
Deceleration
Sequences
1
->
3
4
5
6
7
8
9
10
11
}2
13
14
15
Id
17
IS
19
20
21
~> ~>
23
24
25
20
~> -
2S
29
3d
31
32
Low Alti
CO
0.225
0.936
0-417
0 . 386
0 . 396
1.686
0.650
2.647
1.009
0.628
0.309
1.258
0.330
0.630
0.3S2
1. 130
0.446
1.151
0.352
0.513
1.926
1.295
0.44~
1.156
0.5~5
1.642
0.466
1.071
0.801
0.341
0.807
0 . 9 ~ 8
0.4S2
1.581
1.056
0.540
0.846
tude and
I1C
0.197
0.750
0 . 439
0.426
0.419
1.733
O.S23
2.579
0.970
0.691
0.412
0.881
0.426
0.661
0.617
0.896
0.720
1.014
0.529
0.632
1.718
1.146
0.575
0.984
0.755
1.160
0.749
1 . 630
0.720
0.500
0.940
0.896
0.735
1.469
0.779
0.470
0.970
jj
Modal Ratio
California
^x
0.027
0.182
0.486
1.022
1.542
2.743
0.559
1.554
1.821
CO
0.153
0.771
0.465
0.503
0.634
2.424
0.616
2.431
1.319
2.015 1.178
0.583
2.161
0.755
2.185
0.607
2.379
0.704
2.719
0.559
0.389
0.583
2.403
0.486
2.209
0.554
2.452
0.583
2.579
2.209
0. 585
0.534
2.500
0.534
2.015
2.136
0.651
0.335
2.053
0.405
1.308
0.424
2.255
0.505
2.220
0.434
0.508
1.602
2.361
0.471
2.035
0.591
2.791
0.565
2.474
1.62S
0.45U
0.735
1.92 5
0.55S
2. 100
1.915
0.446
0.510 0.729
High Alti
IK:
0.172
0.706
0-436
0.459
0.451
1.479
0.699
1.933
0.850
0.652
0.350
0.874
0.408
0.652
0.548
0.907
0.652
1 . 1 06
0.513
0.582
1.514
1.176
0.513
0.978
0.676
1.211
0.664
1.572
0.754
0.419
0.827
0.945
0.664
1.539
0.885
0.451
0.885
tude
N0x
0.054
0.373
0.686
1.377
2.027
2.063
0.673
1.121
1.525
1.884
0.808
1.704
1.256
2.198
1.052
1.570
1.211
1.794
0.987
0.583
0.583
1.570
0.718
1.591
0.765
1.591
0.987
1.749
1.525
1.032
0.808
1.704
0.987
1.749
1.435
1.077
0.673
al;i!iissions in moJe/Hmissions in 1975 I-TP (grams/vehiclc-mile/ grams/vehicle-mile)
b
Grains/minute/ grains/vehicle-mile.
102
-------
15 30 45
AVERAGE ROUTE SPEED, ni/hr
60
Figure A-l Average speed correction factors.
18
103
-------
TECHNICAL REPORT DATA
(Please read Inductions on the reverse before completing)
1. REPORT NO.
EPA-450/3-74-046-b
2.
3. RECIPIENT'S ACCESSIOf*NO.
I. TITLE ANDSUBTITLE
Air Pollution Considerations in Residential
Planning Volume II: Backup Report
5. REPORT DATE
July 1974
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
T. M. Briggs, M. Overstreet, A. Kothari,
T. W. Devitt
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
PEDCo-Environmental "Specialists, Inc.
Suite 13, Atkinson Scruare
Cincinnati, Ohio 45246
Vogt, Sage and Pflum, Cincinnati, Ohio
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-1089
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Final
Environmental Protection Agency
Office of Air Quality Planning & Standards
Research Triangle Park, North Carolina 27711
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
Prepared in cooperation with the U. S. Dept. of Housing & Urban
Development, Office of Community & Environmental Standards
16. ABSTRACT
The backup report presents the technical basis for the air quality
estimation procedures presented in the manual. Included are the
justification for selecting only particulates, S02 and CO for study,
and the basis of the air quality criteria levels. A detailed
description of the method for converting outdoor pollutant levels to
indoor concentrations is also presented. Limitations of the manual's
procedures are presented together with recommendations for future
research.
1 7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Land Use, Planning and Zoning,
Design Standards, Permits, Urban
Areas, Residential Areas,
Diffusion
Dl ST RI8UTION STATEMENT
Unlimited
19. SECURI T Y CLASS (Tins Report)
Unclassified
21. NO. OF PAGES
103
20. SECURITY CLASS (This page}
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
104
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