Laboratory Fume Hood Standards,
Becommeaded for the U.S. Environmental Protection Agency
Study dates:
June 14, 1977
to January 15, 1978
Heport date January IS* 1978
Contract No. 68-01-4661
Heport Prepared By
!.X. ChamberUa,
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TABLE OF CONTENTS
Executive Summary Page 1
I. Purpose 3
11. Introduction 3
IH. Laboratory Fume Hoods 5
A. General 5
B. Laboratory Hood Containment 6
Aerodynamics
1. Control Velocity 6
2. Operator Effect 7
3. Air Movement in Lab 8
4. Hood Turbulence 9
5. Discussion 9
C. Design Features for Fume Hoods 10
1. General 10
2. Constant Volume, By-Pass Type 11
3. Auxiliary Air Hoods 14
IV. Hood Tests - "Pre*Acceptance Compliance Hood Tests" 16
A. General 16
B. Test for Compliance 16
1. Standard By-Pass Hood 16
2. Auxiliary Air Fume Hood 18
V. Hood Performance (Operating Conditions Varied) 23
A. General 23
B. Test Series 1, 2, 3, - Tid^ 25
C. Test Series 4, 5, 6, - Tracer Gas 31
D. Test Series 7-Uranine Dye 38
E. Extra Tests 38
VI. Conclusions: 42
A. General 42
B. New Laboratories 42
C. Existing Laboratories 43
D. . Toxicity of Materials - Hood Use 43
VII. Hood Exhaust Systems 43
A. General 43
B. Effluent Cleaning 45
VIII. Hood Surveillance and T-ahoUng 46
Initial and Follow-up Inspections 46
12. Survey of "Regulatory Agencies 47
Appendix 48
Standard Laboratory Fume Hood Specifications and
Performance Testing Requirements
Auxiliary Air SuoDlied Laboratory Fume Hood Specifications
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Table of Concents Continued.
California Adminstrative Code, Industrial Relations
Title 8 Par. 5154.1
Laboratory Fume Hood Sketches
Glossary of Terms
Exhaust System - Orifice Calibration
Supply System Orifice Calibration
Report on the Aerodynamic Performance of a Clean Air
Safety Cabinet Under Various Modes of Operation
Typical Hood Labels
Typical Hood Data Cards
Photographs of TEST Set-ups
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1
LABORATORY FUME HOOD STANDARDS
Executive Suinrnary
The laboratory fume hood if designed, installed, operated,and maintained
properly will provide personnel with a high degree .of protection and allow
the user to work with a wide range of potentially hazardous materials.
The design of the basic laboratory hood and its capability to provide desired
control can be evaluated by existing performance testing procedures. Assurance
that the equipment can meet such criteria is essential.
Hood performance is a function of air flow characteristics as well as quantity.
Not enough emphasis has been placed on these characteristics and to much
emphasis has tradion&lly been placed on quantity. External factors have a
great effect on hood performance. Of these, hood.location and room air
turbulence from any number of sources are of prime concern. Where such con-
ditions exist they should be corrected as the first step in any program to
up-grade laboratory hood performance.
The manner in which make-up air is provided is very important. This air should
reach the hood face in a manner that enhances overall hood performance. It
should "fill-in" the low pressure area in front of the operator without causing
other adverse turbulent conditions.
The control velocities required at the hood face range from 80 FPM for ideal
laboratory situations to 100 FPM for good arrangements. These flow rates
will provide the worker protection desired for any operations that should be
performed in this type of equipment. Flows lower than those proposed do not
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provide the safety factors desired for normal conditions such as operator
movement. Higher flows than those proposed are not required for good
laboratory arrangements and do not improve performance for poor arrangements.
Tests indicate that hood system designs which incorporate true control of
the air in the area in front of the hood operator are safer than conventional
exhaust hoods.
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Puroose:
SSS^SB
Develop and recommend standards for laboratory fume hoods, for the
Facilities Management Branch of The Environmental Protection Agency.
The recommendations are to cover the design, installation, and
operation of such equipment, and If deemed applicable they will be
Incorporated Into the Facilities Safety Handbook by E.P.A. All
recommendations have been developed based on the expertise of the
contractor, review of pertinent literature and guides, as well as
specific tests conducted.
Introduction:
The laboratory fume hood is the primary hazard control device upon
which laboratory workers depend for their protection while working
with toxic or other hazardous materials. Although such hoods have
been in use for many decades, our review of the literature revealed
little scientific data to substantiate the design and control
criteria being specified. Not only was there a lack of data,
erroneous information was often presented as "fact". It is obvious
that proper guidelines must be developed and disseminated, partic-
ularly to architects and engineers who are responsible for design
of laboratory ventilation.
An overall educational program is needed that also extends to the
ultimate user. This is particularly true today because of the many
varied types of hoods (conventional square edge, air-foil, by-pass,
and auxiliary air), as well as those designed for such special uses
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as perchloric acid digestions, distillations, and high level radio-
activity. Similar control devices such as bio-containment equipment
are also often referred to as hoods which further complicates matters.
The variations in terms used also makes the literature somewhat
confusing, particularly to the reader with limited experience in
the use of ventilation as a means of hazard control in the laboratory.
A basic nomenclature and an accompanying sketch has been included
in the appendix.
The training program should cover how to properly use the hood
equipment available and also stress what interferes with good perfor-
manace. Typical items to be covered should include: working as
far into the hood as possible, positioning equipment so as not to
block slots and interfere with airflow, using equipment such as
hot plates or safety shields that have "legs" to raise them off
of work surface, have only necessary items to reduce clutter,
relationship of airflow to sash position, how to recongnize potential
mal-function, and understanding of hood labeling program.
"WaIk-through" surveys were conducted at several EPA operated facil-
ities, to provide a background on the type and range of potential
laboratory hazards that exist and for which a laboratory fume hood
would be expected to provide control. The sites visited were:
1. Environmental Research Lab, Narragansett, 51
2. Region I, Central Laboratory, Lexington, HA
3. Pesticides Laboratories, Beltsville, MD
4. Environmental Research Center, Cincinnati, OH
(Several EPA laboratories at the University of Nevada at Las Vegas
had been visited earlier).
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5
III. Laboratory Fume Hoods:
A. General - THE PURPOSE OF A LABORATORY FUME HOOD IS TO PREVENT OR
MINIMIZE THE ESCAPE OF CONTAMINANTS FROM THE HOOD BACK INTO THE LABORATORY.
This is accomplished by drawing air from the laboratory, past the operator,
into the hood. The concentration of contaminant in the actual breathing
zone (BZ) of the operator should be kept as low as possible and never
exceed the applicable threshold limit value (TLV) for the materials in
question. Since the laboratory worker is seldom stationed at the hood for
long periods of time, it is the short term exposure limit (STEL), the TLV-
Ceiling value (TLV-C) or the peak value as proposed in the American Confer-
ence of Govermental Industrial Hygienists (ACGIH) listing of TLV's, should
be used in assessing the laboratory workers exposure. Uhere no such STEL
or TLV-C h.2s been proposed then the ACGIH suggested excursion factor
should be. applied to the TLV proposed as a 'time weighted average. The often
proposed use of TLV's alone to decide the type of hood and the air velocities
required for control should be discouraged. For materials of unknown
toxicity or where specific toxicity data is not available a system based
on the Vapor pressure/TLV ratio, using an "assumed TLV" selected on a basis
of similar compound would be a better indicator of the potential hazard. In
any event it is the actual exposure outside of the hood that is important.
The ability of a laboratory hood to protect the user, within the exposure
limits noted,will depend on many factors. Of prime concern however will
be the control velocity at the hood face, the effect of the operator on the
air flow pattern at the hood face, air movement in the room,and turbulence
within the hood working space. It is the proper selection and control of
these factors as a group that determines the performance of the hood from
a hazard control standpoint. The need for "group" consideration cannot
be over emphasized. For discussion purposes however the factors will be
reviewed individually.
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6
B. Laboratory Hood Containment - Aerodynamics
1. Control Veloci£y_- It is important to..understand that
there is no single control velocity that will satisfy all conditions.
Velocities of 50 feet per minute (FPM) would usually suffice if the
particle kinetics for aerosols or the molecular diffusion of gases
and vapors were the only forces to overcome. Other "normal" activi-
ties with hoods create air disturbances which must be allowed for.
The vector of the air at the face of the hood is also important.
It should definitely be inward and ideally perpendicular to the face.
Studies conducted to evaluate velocity control included visual (smoke)
and specific gas and aerosol tests (See Section V). Tests were made
while varying the other control factors noted earlier. Based on
these tests, it is concluded that face velocities of 80 to 100 FPM
are adequate if the overall installation can be rated as good to
excellent. The increased turbulence within the hood and around the
operator when higher velocities (150 FPM) were used, compounded the
bad performance of installations rated poor.
The reference point chosen for all observations in the visual tests
noted in Section V Table 3 was located 18" above the hood work surface,
4" into the hood beyond the face and centered between the hood side walls.
The mannequin was stationed as close as possible to the hood with
arms and hands projecting into the hood work area. This observation
point represented a normal operator work area but also one that
was considered difficult to control. This same location was described
as "devastating" in the ASHRAE Report (No. 2438 RP 70) on the effect
of room air challenge on the efficiency of laboratory fume hoods.
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7
Velocities at the face of the hood were uniform (within + 10Z of
the average). A three slot back baffle with adjustable top and
lover slots made it possible to maintain the uniformity for all
tests.
Other velocity related items noted were:
a. Velocities greater than 230-300 FPM interfered with
many operations such as transfer of powdered material
and flame control for bunsen burners.
b. Lowering the sash, thus reducing available face area,
lessened the effect of external sources on velocity
control.
2. Operator Effect - The operator standing in front of the
hood has a tremendous effect on the air flow patterns. The "eddies"
encountered can cause serious losses of contaminant from the hood
to the operators breathing zone. The pulsing that occurs can be
illustrated using TiCl^ smoke swabs, and the potential for short
term peak exposures to contaminants is obvious. It should be stressed
that these are not steady state and testing for same must be by
tests where instantaneous peaks can be detected.
Proper use of make-up air, with emphasis on filling the void or
minimizing the low pressure area in front of the operator, is a
primary goal for good hood performance. The tests in Section V
Tables 3 through 9, illustrate that properly operated auxiliary air
hoods offer significantly greater safety to the operator.
Based on these evaluations, it is concluded that make-up air, even
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8
in non-air conditioned laboratories, should be provided in a controlled
manner that will reduce the "operator effect", but not result in
positive displacement or drag-out of air from the hood enclosure.
3. Air Movement in the Laboratory - The effect of air move-
ment within the laboratory on the performance of hoods is directly
related to hood location and influence from air supply systems. Hood
locations must be away from doors, windows, and pedestrian traffic.
AIR FROM THESE SOURCES CAN BE AT VELOCITIES SEVERAL ORDERS OF
MAGNITUDE GREATER THAN THE HOOD FACE VELOCITY, creating potential
for dragout or displacement of contaminated air from the hood.
Ceiling and wall diffusers for distribution of make-up air are also
serious potential sources of interference. Air from such outlets
should either be controlled to assist in the performance of the hood
or directed so that the energy is lost before entering the zone of
influence. Experience has indicated that air from make-up systems
should not exceed 20-25 FPM, in the hood face area (measured with
hood exhaust "off").
It should also be noted that air drawn from adjacent areas (by
the hood exhaust system) must still enter in a manner that does
not create excessive turbulence.
Pedestrian traffic should be minimal. Location of a hood at the
end of a room or bay, where the operator is essentially the only
one who enters the zone of influence, is ideal.
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9
Tests results in Section V again indicate that providing air in a
controlled manner to the hood area enhances the overall efficiency
of hood operation.
4. Hood Turbulence - The air upon entering the hood, is
drawn past equipment and sources of contamination, toward the exhaust
slots. Much of the air within the hood is in a turbulent state.
At airflows greater than needed to provide a good vector and contain
the contaminant, cue turbulence can be excessive causing a greater
"rolling effect" in the hood chamber. This increases the potential
for greater mixing of contaminated air and room air at the hood face.
Under many poor laboratory hood arrangements, this combination of
poor arrangement and greater interior turbulence results in excessive
loss of contaminated air to the room. Several smoke tests at 150 FPM
face velocities for other than a good hood arrangement with controlled
make-up air, produced obvious losses greater than those noted at
lower flows. The pulsing noted was very severe.
5. Discussion - The use of a ventilated enclosure to
contain and exhaust a contaminant depends on providing an airflow
sufficient, but not in excess, and in a manner that overcomes or
minimizes the effects of the operator and other exterior sources
on the proper aerodynamic performance of the hood. Although no "one"
exhaust rate is ideal for all situations, a flow based on 80 to 100 FPM
hood face velocity will provide adequate control for the majority of
hoods, if such meet the other criteria noted for good laboratory
arrangements. Again if the arrangements are not satisfactory,they
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should be Improved rather than increasing the velocity which may
veil complicate matters.
C. Design Features of Laboratory Fume Hoods
1. General - The basic fume hood today consists of a super-
structure which houses the actual work, .space and a base unit on which
it is placed. There are, of course, many specialty type units such
as walk-in hoods, perchloric hoods, etc. The materials of construc-
tion can vary widely with interiors from the standard transite lined
unit to the stainless seamless type. It is intended here to develop
standards for a good basic unit, including both auxiliary air and
noil-auxiliary air types. Special application would require exten-
sions of these design features.
The laboratory hood is part of an overall system, involving the
laboratory, a duct system, a fan, and often Includes effluent cleaning
devices. The ultimate user has the right to assume that if used
properly the hood and system will provide him a means to work with
hazardous materials without undue exposure. It is essential there-
fore that each portion of the system be chosen carefully. This
means that performance criteria should be specified and satisfied.
For example, the laboratory hood manufacturer should provide proof
that the unit in and of itself performs satisfactorily under the
conditons required. Materials should meet corrosion resistance
standards, fans should be AMCA rated, plumbing fixtures and electrical
outlets should meet existing codes. Actual specifications and testing
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procedures for checking aerodynamic performance of fuse hoods have
been developed and are included in the appendix. Some of the major
equipment manufacturers have the capability to perform such tests
and independent testing laboratories are also available. There is
no reason for a purchaser not to require a performance test. The
pertinent features for the two basic fume hood types are discussed
in the following paragraphs and these should provide the standards
for design.
2. Constant Volume - By-oass Type - The laboratory hood is
often an intergral part of the building exhaust system. The volume
of air exhausted should be constant and this can be achieved by
having a by-pa^s through which room air can pass even if the sash
is closed. The by-pass sizing and design must be such that;
a. The total air flow is essentially the same at all
sash positions.
b. The control velocity as the sash is lowered must
increase to twice but not more than three times
the velocity for full open sash position.
The upper limit (three times) is an absolute
ma-rimim that can be allowed and have a TirlniTmnn
effect on such operations as the hand!lug of
powdered material or the operation of buns en
burners. The lower limit (twice) represents a
pratical relationship between by-pass size, sash
operation, and size of hood superstructure.
c. The by-pass should provide a sight-tight effective
barrier between the hood work space and the room
when the sash is lowered.
d. The by—pass opening should be dependent only on
the operation of the sash.
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Airfoil inlets have been proposed by many investigators. A horizontal
bottom airfoil, raised approximately one inch above the vork surface
so that air constantly, vents under it offers significantly improved
control. The vertical foils on the sides result in a slight improve-
ment by minimizing the eddies caused as air enters the hood. The top
airfoil does not measurably change performance for the bottom edge
of the sash introduces some eddying. The basic specification should
require the bottom and tvo side airfoils.
The work surface should be of the recessed type. Spills can be
effectively contained by the retaining lip. The front raised edge
should extend into the hood sufficiently so it is beyond the air-
foil but not be wide enough to be used as a shelf enabling worker
to move equipment out to the face opening. Although the materials
of construction can vary for other portions of the superstructure
it is recommended that the work-surface be stainless steel or molded
epoxy resin.
The interior height for basic hoods has been governed by standard
stock sheet sizes, like transite for example which are usually
41 x 8'. Th-Ls has enabled manufacturers to produce interior heights
close to 4 feet and this has been acceptable.
Height of the sash opening has varied between manufacturers, usually
from 26" to 36". It is desirables to keep the sash height as low
as possible for, as indicated earlier, this reduces the face area
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and effects of outside Interferences are lessened. It also reduces
the air quantity required to maintain the control velocity specified.
A full face opening of 31" to 32" high has proven to be generally
acceptable.
Side walls are required for service piping, wiring, and sash weights.
Thickness can vary but a should be set to assure that valuable
work space Is not lost. Experience indicates a wall thicknesses of
approximately 4" will accomodate controls, vertical foils, and
service outlets.
Width of hood is usually optional with the user, and standard models
are available from manufacturers in width of 3 to 8 feet. The four,
five and six foot models are by far the most popular. Hoods larger
than 6 to 8 feet present some sash problems and usually require
multiple sashes. Our experience indicates that any size can
usually be attained by combination of standard units.
Depth of hood does not. have a critical dimension, it is also related
to stock size and other adjacent laboratory furniture. The mayi-minn
pratical depth should be attained. The plenum formed by the back of
hood and the back baffle that has 3 slots, (2 adjustable and 1 fixed),
need not detract more than 2" from the depth of the work area. A
screen, with equivalent free area to the full open bottom slot area,
should be positioned to assure that blockage of slot is not possible.
Height of hood is not critical for most, standard installations.
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Required room celling height is usually determined by height of
unit with fully raised sash.
Lighting should be of the fluorescent type, be serviceable from
exterior and be displaced or sealed to assure that vapors do not
enter the light fixture.
The basic hood should also be able, if required, to accept a
supply air feature, without undue exposure to installers and
laboratory personnel.
Use of Horizontal Sliding sashes may be adaptable as an air
saving device in some instances. It is our opinion however Chat
they are not easily accepted by the worker, tend to be cumbersome
and are frequently removed by laboratory personnel. Their use as
a safety shield tends to be exaggerated as well as limited.
Horizontal sliding sashes are not adaptable to good by-pass or
auxiliary type hoods. This type of sash provides a square edge
along the vertical side of the sash opening and increased eddying
results.
3. Auxiliary Air Hoods - Auxiliary air hoods are being
proposed, particularly with todays accent on energy saving, as a
real means to reduce air conditioning costs. The initial savings
on air conditioning equipment plus reduction in operating costs
for such equipment is obvious. Although this potential is of
utmost importance to those responsible for cost control it is
important to stress several points:
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a. The auxiliary air feature must not;lessee the
safety features in any way, for this is the prime
reason for having the hood in the first place.
b. It is possible for the awef llary air hood to be
safer than the standard exhaust hood, if it is
designed and maintained properly.
c. There is little or no saving on heat, for the
auxiliary air must be heated to essentially room
temperature during cold weather months.
Many available models however have features that may present poten-
tially hazardous situations. It is essential therefore that this
equipment be selected on a performance basis. A detailed specification
has been included in the appendix.
It is essential that all air be supplied outside of the hood face.
Any model that Introduces air behind die sash must not be used for
it reduces the control velocity at the face and it could actually
pressurize the work chamber should the exhaust flow be reduced.
Models that direct auxiliary air into the hood at any sash position
can also result in unsafe conditons.
The auxiliary air hood should provide satisfactory performance
up to at least 702 supply and with auxiliary air temperatures of
up to 20 degrees F higher than room air temperature.
Any auxiliary air system, to perform satisfactorily, must be able
to remove the energy from the supply air, leaving a duct at velocities
of up to 2000 E?M or greater, and then distribute it evenly at low
velocities in an essentially laminar flow pattern so that it can be
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entrained efficiently by the hood exhaust. This must be achieved
within a short distance and without introducing high static losses.
The features noted for the standard hood would all be applicable
to the auxiliary hood, including the by-pass arrangement.
The potential for using this type hood with low supply quantities,
even if not connected to an outside source of air, to achieve the
improved performance as a result of controlling the air flow patterns
when an operator is involved should not be overlooked. Test results
in Section V, verify this.
Hood Tests - "Pre-acceptance Compliance Hood Tests":
A. •General - A standard airfoil exhaust hood, an auxiliary model
of same, and a bio-containment unit were used for Initial tests.
Specifications developed from these studies were used by EPA to
purchase and provide a fume hood that could be used both as a standard
exhaust or an auxiliary air type as desired. This hood was then
used for all subsequent testing.
B. Test for Compliance with Performance Specifications - These
tests are to determine whether the unit, as provided by the manu-
facturer, can operate satisfactorily when installed properly.
1. Standard By-pass Fume Hood - The unit was set-up in
the test room and the outlet connected to the exhaust system which
has the capability of varying airflows and has a calibrated orifice
as required. (Copy of Calibration Sheet included in Appendix).
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The test area was checked and found free of cross drafts. (Less
than 10 EPM as determined using a calibrated thermal anemometer).
With the sash in the fully raised position the open face area was
measured and found to be 13.8 sq. ft.
The exhaust system was then turned on and set for 1380 cubic feet
per minute (CFM) to provide an average face velocity of 100 FPU.
The uniformity of the velocity was checked by taking 9 velocity
readings as specified, using a calibrated Alnor velometer. The
readings varied from 95 to 105 FFM which is well within the limits
set.
Using a cotton swab and titantiurn Tetrachloride, the entire hood
face was traversed and no back-flows were detected. The vector of
the air entering the hood was essentially perpendicular to the
face and steady.
With the sash still in the raised position a one minute smoke bomb
was discharged within the hood work space at bench level. The hood
quickly filled with smoke and then cleared rapidily. Some "rolling
effect" was noted in the upper hood area, but no losses could be
detected.
The sash was then lowered to a point six inches above the work surface.
At this point the by-pass was partially open. Three velocity measure-
ments were taken across the open face area and the average velocity
was found to be 230 FPU.- This satisfied the specification for a
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velocity increase of 2, but less than 3 times the design velocity.
The manometer reading (for calibrated orifice) was unchanged
indicating no change in total airflow.
The sash was then lowered to the fully closed position and the
nanometer reading checked. Again no change was noted indicating
total flow still unchanged. Observation of the by-pass showed it
to be sight-tight and it satisfied the barrier requirement.
It was determined that the laboratory hood as tested met the
performance for, the constant flow, standard by-pass unit as specified.
2. AmHUaTy Air Laboratory Fume Hood - The Auxiliary air
laboratory fume hood consisted of the basic hood as tested in Section IV,
Bl., to which a supply air plenum was attached.
The plenum was easily mounted so that the air would be supplied
exterior to and above the hood face. The chamber did not interfere
with the operation of the sash or by-pass and no dismantling of
the exhaust duct was required.
The supply air duct was attached to the inlet of the supply plenum.
The supply air system also has a flow regulating device, a calibrated
orifice (calibration curve in appendix), and an electrical heating
unit for varying the supply air temperatures.
a. The exhaust system was turned on and set for flow
of 1380 CIM (100 FPM Face Velocity)
b. The supply system was turned on and set for flow
965 CFM (702 of exhaust volume). (Room air and
supply air temperatures equal + 2°F).
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c. The velocity at the discharge of the supply air
pieman was checked using the thermal anamometer
and found to average ISO FPM, and did not exceed
200 IPM at any point.
d. A TlCl^ swab used to traverse the hood face showed
the air vector to be good and no reverse flows
were detected.
e. A smoke bomb (1 minute size) was set-off within
the hood work space at bench level. Hood cleared
quickly, some roll to air in upper chamber, but
no losses, even at bottom of raised sash, could
be detected.
f. A one minute smoke bomb was then introduced into
the supply air (prior to the fan for good mixing)
and the patterns of the air stream as it left the
auxiliary air chamber and entered the hood were
observed. The smoke indicated a smooth essen-
tially laminar flow with excellent entraimaent
of the supply air.
g. Smoke test as in (f) above was repeated twice
once with the sash fully.closed and all of the
smoke was observed entering through the by-pass
opening, and secondly with the sash raised 8"
above the work surface. The supply air entered
the by-pass and through the sash opening with
essentially total capture being attained.
h. Uranine dye tests were conducted as outlined in
the specifications (copy in appendix) to deter-
mine the capture efficiency. Results of these
tests are compiled in Table 1.
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TABLE 1
Capture or Entralnment Efficiency
Conditions of Tests No. of Tests Results Obtained Percent
Conducted (X Capture) Entralnment
. , (Avr)
1380 CFM Exhaust 965
CFM Supply (70-30 ratio]
Room Air 71°F Sash
fully raised
4
98.5
97.0
97.2
98.1
97.7
Same flow conditions
2
95.2
95.6
Room Air 72°F
96.0
Supply Air 92-94'F
Based on these results the auxiliary air hood performance exceeded the specifications.
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1. The hood loss test under imbalance conditions
vas then performed as outlined in the specifi-
cations. This represents the condition where
the supply air volume is maintained, but the
exhaust air volume is reduced to the point where
CFM exhaust equals CFM supply.
The 965 CFM Supply was maintained and the exhaust
flow reduced from 1385 to 965 CTM. The temper-
ature of the supply air was adjusted so as to
equal the room air temperature.
The uranine dye studies were then conducted as
noted in the specifications and the results of
3 separate tests are shown in Table 2.
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TABLE- 2
Hood Loaa Under Imbalance Conditions
Conditions of Test
Test No,
Time
Percent Loss
Left Side - Right Side
965 CFM exhaust
1
45 min.
0.02 0.02
965 CFM supply
Room air and Supply
2
60 mln.
0.007 0.003
air Temperature 73#F
3
60 mln.
0.006 0.004
Based on these teats It was determined that the auxiliary air hood did not exceed the losses
permitted.
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V. Hood Performance (Operating Conditions Varied);
A. General - Several tests were conducted to evaluate what
effect interferences outside of the hood had on the overall per-
formance of a good laboratory fume hood. The outside interferences
included an operator stationed at face of hood, room air turbulence,
and various room make-up air arrangements. The effect of changes
in control velocity was also studied.
A sketch of the basic test lab where this work was performed is
included in the appendix. The lab arrangements made it possible
to have the make-up air drawn into the room through large double
sliding doors, partially open doors, through ceiling diffusers, or
through large veil spaced vail openings. It was also possible
to introduce outside air at controlled flow conditions. The room
conditions were rated for each test series, and the criteria for
ideal, good or poor are as follows:
Ideal (1) Excellent location, end of room or bay, no door or
window problems.
(2) Essentially no pedestrian traffic, other than hood
operator.
(3) All of the required laboratory hood make-up air,
drawn or induced, so as to enhance over-all hood
performance. For example a properly designed and
located perforated ceiling section or well designed
auxiliary air type hood plenum.
(4) No other grilles or dlffusers exist that produce air
at measureable velocities in the hood area.
Good (1) Good location, no door or window problems, and not
on a main aisle.
(2) Minimum traffic other than hood operator.
(3) Have air supplied to lab so velocity from dlffusers or
grilles does not exceed 25 FPM in vicinity of hood.
Poor Where any one or more of the conditions noted above
are not met.
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Note: The following conditions are typical of those introduced,
one at a time, which had a sufficient effect on air flow patterns
in the test laboratory to change the room rating to poor.
a. Make-up air drawn into the room through a partially
open door (3 sq. ft. opening) located approximately
8 ft. behind the operators station in front of hood.
b. Make-up air drawn into the test laboratory through
a ceiling diffuser (1 sq. ft. free area) in such a
manner as to cause turbulence in the area directly
behind the mannequin.
c. Pedestrian traffic to and from the hood or passing
behind the mannequin.
For all tests conducted, there was sufficient equipment set up in
the hood to simulate normal use and the mannequin was stationed
directly in front of and at the center of the hood face with hands
and forearms projecting into the work area. The "breathing zone"
(BZ) samples were taken just at mouth level. The sash was fully
raised unless another position is specifically noted in the tables.
The aerodynamic performance of the fume hood was also rated for
each test series. This rating indicated the laboratory fume hoods
capability for containing contaminants and minimizing potential for
operator exposure. The ratings used were; not acceptable, marginal,
acceptable, and excellent. Note:
a. Not acceptable - indicates that there is a high
risk of the operator being exposed due to exist-
ing operational parameters over which he has no
control.
b. Warrinai - indicates that the risk for exposure
is still greater than desired.
c. Acceptable- - operator exposure potential reduced
to a satisfactory level but significant improve-
ment still possible.
d. Excellent - equipment provides maximum protection
for its type and application.
-------
B. Test Series 1, 2, & 3 - Observations using Titanium
tetrachloride smoke trails, offered a good visual method to check
on the control provided under different arrangements. The point,
in front of mannequin, 4" in from face of hood and 18" above the
work surface was selected for it is a typical location where opera-
tors would perform such tasks as material transfers, and it is also
in the zone where eddy currents are very prominent making contain-
ment difficult.
The results have been compiled in Tables 3, 4 mid 5. The "non
uniformity" of flow patterns, particularly in the zone being
evaluated was very striking. Pulsing was obvious and considerable
variations in rate and intensity noted. For poor room conditons,
increasing face velocities to 100 7PM made a slight improvement
but further improvement at velocities up to 150 FPM was not evident.
Acceptable performance was never achieved when poor room conditions
eaisted regardless of the control velocity used.
With room conditions rated as "good", the pulsing air problems
could still be seen at lover flows. When 100 FPM control velocity
was attained, the flow vector improved sufficiently to indicate
acceptable performance. Increasing the velocity to 150 FPM did not
noticeably improve conditions. (Table 4, Test Series 2).
Under "idea!?.1 room conditions and use of standard hood or where the
auxiliary air hood was used (see Table 5, Test Series 3), the improve-
ment attainable by filling in the void or low pressure area in front
-------
of operator is very obvious. At 80 F?M velocity control was
sufficient to overcome normal operator movement. Increasing to
100 FPM did not noticeably improve conditons, and further increase
to 150 FPM caused noticeable pulsing but did not hamper containment.
-------
TABLE 3
Hood Performance - Teat Seriea ^
Baaed on Visual Observations of a Point Smoke Source Located A" In from Plane
of Hood Face Opening, 18" Above Work Surface and Directly in Front of Mannequin.
No.
Type of
Hood
Room
Special
Average
Face Velocity
Observations of
Performance
1
Standard
Poor
Room make-up.air drawn
through door partially
open in wall opposite
hood (3 sq. ft. opening)
50
No real control
Not Acceptable
2
Standard
Poor
Same
80
Still extreme pulsing
Not Acceptable
3
Standard
Poor
Same
100
No obviour change
Not Acceptable
4
Standard
Poor
Same
150
Increased turbelance
reversed flows less
frequent but increasec
intensity
Not Acceptable
5
Standard
Poor
350 CFM Hood air sup-
plied through a ceiling
diffuser (1 sq. ft. frae
area) so ao to produce
turbulent condition
behind operator
.50
No real control dbvi-
ous leakage. Worse
with pedestrian
traffic
Not Acceptable
6
Standard
Poor
Same
80
Only very slight over-
all improvement. Less
involvement due to
traffic
Not Acceptable
7
Standard
Poor
Same
100
Better containment
but still pulsing
Not Acceptable
8
Standard
Poor
Same
150
Containment same as #7
overall turbulance in
Not Acceptable
-------
-------
TABLE 4
Hood Performance - Teat Series 2
Based on Visual Observations "of a Point Smol^e Source Located 4" in from Plane
of Hood Fece Opening, 18" Above Work Surface and Directly in Front of Mannequin.
Type of
Room
Average
1
Standard
Good
£i JL LKC L
Make-up air- drawn into
lab through full open
door. Located on oppo-
site wall—(36 sq. ft.
of opening) .
50
bmoke-Pattern
Flow obviously revers-
ing. Easily drawn out
by pedestrian traffic
behind operator.
Rating
Not Acceptable
2
Standard
Good
Sams
80
Still pulsing and
intermittent reversing
Not as easily inter-
fered with by walking
past operator.
Not Acceptable
3
Standard
Good -
Same
100
Better air vector -
with slight overall
improvement.
Marginal
A
Standard
Good
Same
150
No significant improve
ment noted over il3.
-Marginal
-------
TABLE 5
Hood Per.'xmsnce - Test Serloa 3
Based on Visual Observations of a Point Smoke Source Located 4" in from Plane
of Hood Face Opening, 18" Above Work Surface and Directly in Front of Mannequin.
^o.
Type of
Hood
Room
Special
Average
Face Velocity
Observations of
Performance
1
Standard
Ey-Pasa
constant
volume
Ideal
Make-up air ur.ifivs.ly
drawn thru 1.53 6!
ceiling opening. Locatec
over and to front of
hood.
50
QlUyMJTtlL LCLU
No positive vector -
easily reversed by
operator movement.
iuitinR
Nof Acceptable
2
Same
Ideal
Same
60
Some direction to
vector but not strong
enough. Still easily
pulsed by operator.
Ho significant
reversal.
Marginal
3
Same
Ideal
Same
80
Good vector, operator
movement had minimal
effect,
Acceptable
4
Same
Ideal
Sarr.a
100
No significant
improvement over #3.
Acceptable
5
Same
Ideal
Same
150
Strong vector pulsing,
Significant turbulancc
in hood. No notice-
able operator effect.
-Marginal
6
Same
Ideal
40% of air required for
hoqda taken fro^ room
and passed thru auxil-
iary air plenus,remain-
50
No reversals noted
but air vector very
weak. Slight inter-
ference by operator
Marginal'
-------
No,
TABLB 5 (cQnt,)
l-ood P — 'r.-r-cnce. - Test Scries 3
Baaed on Vieual Observations of a I'oiiit Smoke Source Located 4" in from Plane
of Hood Face Opening, 18" Above Work Surface and Directly in Front of Mannequin.
Type of
Hood
Standard
By-Paas
constant
volume
Room
Conditions
Specic-.l
Effect
Ideal
Average
Face Velocity
FPM
Obeervationa of
Sraoke-Pattem
40% of air require: ! for
hood. Taken frcw room
and passed thru auxil-
iary air planus; reir.ain-
ing 60% also frsa room.
SO
Good vector excellent
control, minimum s>
turbulence.
Performance
Rating
Excellent
Same
Same
Auxiliary
Air Hood
Ideal
Ideal
Ideal
Same
100
Seme
150
70% of air required for
hood supplied frora a
source outside of the
laboratory. through
the auxiliary air
chamber-, the regaining
30% from rooia.
80
No noticeable improve-
ment over #7.
Excellent
Interior hood turbu-
lence significantly
increased, Contain-
ment still good.
Excellent
Very good vectors. No
reversal^ normal oper-
ator movement no effem
^Traffic behind opera-
tor minimal effect.
Excellent¦
-------
-------
C. Test Series 4, 5, 6, Tracer Gas Studies - Gas studies were
conducted using sulfur hp.xaf louride as the tracer gas. This gas was
chosen because it is essentially non-toxic and inert. The detector
used was a Model SF6B unit manufact\ired by Scientific Systems Corp.
This unit has an electron capture detector cell and can be used in
a chromatographic mode or a continuous operating mode. This permits
sampling over a wide, range of concentrations.
Mecusuranciuts mads, because of the pulsing mentioned earlier, deter-
mined primarily instantaneous levels of gas. In Tables 6, 7, and 8 the
pulse range as indicated by the instrument has been converted to
percent loss. A total of 10 measurements were made for each test
and the high and low results reported.- Also 4 measurements were
taken with operator movement and the highest peak reported.
Again with poor room conditions, poor hood performance was attained
and increasing hood control velocities did. not make it possible to
get satisfactory control.
With good room conditions, the 100 FPM velocity provided acceptable
performance when standard hoods were used and very good performance
was attained at 80 FPK when auxiliary air hood was used. In both
cases higher velocities did not appear warranted.
-------
The "ideal" tests (Table 8) again emphasize the improvement attain-
able, at 80 FPM, when outside interferences are eliminated. Although
at 100 FPM some slight improvement was noted for operator movement, no
further improvement could be shown for 150 FPM.
-------
TABLE 6
Hoo^ ??erl:onn5aca - Teat Series 4
Baaed on Tracer Gas (SF6) HsnsureEients. Eaieeion Source Located 4" in
from Plane of Hood Opening, 13" At:ova Work Surface, and Directly in Front
of Mannequin. • MeasnraKants Via da ia Breathing Zone of tfanaequin,
No.
Type of
Hood
Standard
Standard
Standard
Standard
Standard
Room
Conditions
Effect
Poor
Poor
Poor
Poor
Poor
Hake-up air dr:-.:.>zi from
next room through pzvt
tially oper. door
(3 sq. ft.)
Sair.c
Same
(
350 CFM Hood Eir5 suppl-
ied thru a coiling
diffu.ser (1 sq. ft. free
area) so as to produce a
turbulent condition
behind operator. I
Avarage
Faca Velocity
FPH
50
60
100
50
Perc-nt; I-oas
nad Comment?
Range 0.002% to 0.12%
Peak 0.16% with opera-
tor movement; minimum
pulsing on meter
Range <0.00002% to 0.092
Peak 0.16% with oper-
ator movement. Notice-
able meter pulsing.
Range <0.00002% to 0.45%
Peak 0.58% with opera-
tor movement. Meter
pulsing about same as //2
Range <0.00002% to 0.35/
Peak 0.45% with opera-
tor movement- very
erratic meter pulsing.
Range 0.24% - 0.85%
Peak 1.8% with operator
movemen t.
Performance
Rating
Not Acceptable
Not Acceptable
Not Acceptable
Not Acceptable
Not Acceptable
Standard
Poor
Same
80
Range 0.09%- 0.58%
Peak 0.73% with opera-
tor movement.
Not Acceptable
-------
V
-------
TABLE 6 (cont.)
?iood ?eT-'oTL7.".:'iVtre - Test Serisa 4
Based on Tracer Gas (3?6) Ilsasuriraants. Emission Source Located 4" in
from Plane of Hood Opening, 1B:! iuiovc Work Surface, and Directly in Front
of Mannequin. Measureiaentc Hade iti Breathing Zone of Kanaequin,
Average
Type of Room Special Face Velocity Percent loss Performance
Hood Conditions Effect: FPH and .Comments RatinR
7
Standard
Poor
B
350 CFM Hood £>ir, suppi-j
led thru a ceiling
diffus^r (1 sn. it. frat-
area) so as. to produce a
turbulent condition
behind operator.
100
Range 0.04% to 0.35%
Peak 1.3% with operator
movement. Very erratic
meter pulsing.
Not Acceptable
8
Standard
Poor
»
Same
150
!
{
Range 0.002% - 0.35%
Peak 1.3% with operator
movement. Very erratic
meter pulsing.
~
1
|
Not Acceptable
u>
¦£>
-------
-------
TAP.I.E 7
F- Test Sirica 5
Baaed on Tracer Gas (SVC) ur^nts. •Esiesi.ir. Source Located in
from Plane of Hood Opcnir^, 1Z>" Above Work Surface, and Directly in Front
of Mannequin. • MaasuraascaUe rlrde in Breathing Zona of Kanaequir.j.
Type of
Roon
opc-cif.l
Avaraga
Facs Velocif:".
Percent loss
1
Standard
Good
A-i j. w .. CI Li
! I
Make-up cir fit.-.:£o f 50
lab through Il.1 .1 cp.;n |
double door locate-;: on t
opposite X-/C.11 ("i55 3-1.f
¦ I I ^
Range 0.0035% to 0.005%
Peak ¦ 0.08% with
operator movement.
Kacinp;
Hot Acceptable
2
Standard
Good
Saci | 80
)
*
i
\
1
Range 'i-"i
.liary nlr eh'.V:.:ar. Tha '
other 30% dra;or. Lr.zz i
room through single door
(18 &o: ft.)
Range ilO-Of,.detected./
CO.00002%. Peak 0.0008%
with operator movement.
Acceptable
!
6
Auxiliary
Air Hood
Good
i 1 - ICG
1
!
1
1
!Rnn?.e iv.:nu ' detected
$.00002%. Peak ND with
operator movement.
Excellent
J
-------
Based on Tracer Cas (Sl-'if/j „ 3. 'Emission Source Located A" In
fron Plane of Hcod Opening, I":''1 A-y>v.i tfork Surface, and Directly in -Front
of Mannequin. ¦ Meaeuremar.ti -kta in £reathing Zona of Mannequin.,
Typa of
HoOEl
Svs^cJ
flfr* Y\"*
•- v ~~ O
Face Velocity
Percent; I-osa
Performance
Standard
Ideal
i
i
Room maks-i'.p • i;
unifornly dreva
1.5:x6' l'COjC- 1
ingj located ovi-r and >
to fronc of hoorZ. 5
am
!
c n i
\
\
!
1
j
Range <^0.00002% to J
0.0G12Z. Peak 0^06% J
V7iJth operator -maveraen!
pacing
Hot Acceptable
Standard
1 ——
Ideal
>
Sec ^ i
!
3D i
i
Range none detected
<0.00002%. iJeak
none detected<0.00002a
Excellent
Standard
Ideal
i
f
100.
Saiue as f;2
Excellent
Standard
Ideal
\
153
Same as -:2
Excellent
Standard
Ideal
40% of air requira,--, •
for hood, taken ii-'oia ;
roosi and pas3ad ;
through auxiliary ;;.lr 1
plenum, regaining CCS ;
also fro!?, vcoc. j
56
Range <0.00002% to
0.0009%. Peak 0.035%
with operator movement
Marginal
Standard
Ideal
1
S£ir.3 j
SO
l Range detected
<0.00002%. Peak (with
'operator movement)
! still <0.00002%.
Excellent
Standard
Ideal
Sar;-?. 1
10 D
i
\ Same as i;6
Excellent
Standard
Ideal
\
j
j
150
j
! Same as #6
i
1
Excellent
-------
Hooi
Baaed on Tracer Gas (SIrcV
from Plane of Hood Op^r.-iv.3
of Mannequin. • Heasurenan
:o.
Type of
Hood
Rooa
Conditions
Auxiliary
Air Hood
Ideal
70% of a"..- :
hood Buppli.-
source Dijr.sj
l i -i L 1 1 ci \Tj i] _
The reru:,inA:-
I'ocm. (Dcub
opposite i.x!
36 sq. Et.)
LE 8 (cont.)
a - Teat Series 6
v.3 . 'Emission Sourca Located 4" in
o Work Surface, end Diractly i:\ Front
Lraathing Zona of HiinnequinT
Avar-age
Pace Velocity Ferrari* 1-oas Performance
YPU End Comments . Fating
t • i
i , I
:::¦} £0 ! Ranse <0.00002% i Excellent
' ' Peak <0.00002% !
-------
D. Tent Series 7 - TJraaine Dye Studies - Tes Cs based on Che:
generation of a fine uranine aerosol were conducted. The samples
were collected "jn-a.l y/ed in a manner sinilcvc to the procedure
oui/.lined in tha hood performance specifications (Appendix) .
A total, of 6 ccurpic?, vc-.j:?. i'-.kaa fur i;es;; situ-itioa, the
sampling time was 10 minutes in each case, unless otherwise noted
in Table 9; A^ain the range of high and'low are reported as percent
loss. ''Iso s. ent of !:hrae, one rn.nnt:?. ^r-.~plcc v.".r: ta-'.en for each
"I 1 :.i ; • o fV:\ <".5 '.'> ^ V "j L / O ?. ? C'\ A '" • ' 3 >
/ cn not osTjaci.Ou cli-.e to u'.u; f:rva;..f.c ii*.n.i^lioc\
that e:cists. However the trend obviously correlates with the other
test results wb.era ideal conditions and 30 to 100 FPM face velocities
produce very good hood performance for both standard and auxiliary
air hoods. Good conditions follow the same pattern and poor situation
are not significantly improved at higher flows.
E. Other Individual Tests of Probable Interest
1. With the indication of excessive "top roll" within
the hood at the high (150 FPM) flow rate, a series of sraoke teats
were conducted where a 1 minute smoke bomb was set-off so the
smolce would be carried up into the upper hood section. With
-------
Hdoe X-crUoVw-a.r.i - Tect Series 7
Based on Uranine Dye Tests. Aerosol generated i'li head snd dispersed through a 21 x 5 chamber located
4 Inches in froia face of hood opening l£t3 i*;oVv. iroti, iis-fBce; 'Air Eaciplec obtained in breathing zone
of mannequin.
Mo.
Typa of
Rooa
Average
Face Velocity
Percent Lobs
Performance
1
S tandgrd
-7—7
Poor j
i
!
!
Make-up r.ir i:r.r
open door, (3 £u.) J
i
<
50 1
!
Range 0.033 to 0,14
Higheut Sftort Term
.(UST) 0.21
Kacing
Not Acceptable
2
Standard
!
Poor, j
i
1
}
S-.-i 1
£0
Range 0.02 to 0.11
tIST 0.36.
Not Acceptable
3
Standard
Poor 1
i
£ 31U& 1
100
Range 0.022 to 0.16
IIST 0.72.
Not Acceptable
4
S tandard
i
Poor
£cv.-.;
150
Range 0.025 to 0.27
HST 1.35.
Not Acceptable
5
Standard
Good
Make-up air drthru
full doul-la denr (?c. c.i.
fc.) or. orr.ariui vkLI.
SO
Range 0.002 to 0.04
IIST 0.C44.
Marginal
j
S tandard
Good
100
Range 0.0009 to 0.0064
IIST 0.018.
Acceptable
r
Standard
Good
o 3 ni £
150
Range 0.0903 to 0.0051
LIST 0.003.
Acceptable
Auxiliary
Air Hood
Good
70% air for h.od from
outside of lab thru
auxi.lia-"y air chamber.
Other 30.% dr^r?:> ^; f;a
room uhtu cin^Ia door
(18 G q . ft..)
SO
Range (none detected)
without operator move-
ment <0.00002% (45
minute tests required)
Excellent
|
-------
Based on Uranine Dye Tests. Aerosol \
A inches in from face of hood opening i6': cbov.;
of mannequin.
No.
Type of
Hoe?
9
Auxiliary
Air Hood
Good | ,:-
10
Standard
Ideal
Air c..:.:r.-
opcniiv; (i ;..
located sv;l"
of iicnd-
LI
Standard
Ideal I S '
L2
Standard
Ideal
40% .-.t- • v
roon ¦- ccd
auxiliary in.
.3
Auxiliary
Air Hood
Ideal
70% air frci; r.
source .uiru .
chamber r,:' cr
roots (double cl.
36 eu. ft,}.
!
A-n.:' 9 (c-cnr.,)
n -- Tc^r. i :.r. 7
d .-rid dispersed thresh a 2" 3; 5" chamber located
surface'. " Atv: aatnplarj obtained in breathing zona
j
OiSl
-rs
t-pif
100
SO
100
o ->
so
'Jercent Lobb
Comments
Performance
Rating
San- as i'8
Hone defected
j<0.00002% (45 minute
! teste)
I S a:r.- as H10
11-13ne del:acted
I<0.00002% (45 minute
j teste) .
SNone detected
<0.00002% (45 minuto
I tests) .
j Excellent
Excellent
Excellent
Excellent
Excellent
-------
"poor" room conditions, particularly when turbulence was caused by
make-up air from the ceiling diffuser, there was obvious excessive
mixing and drag-out that both entered the BZ of the worker and
the general lab area.
2. With the standard hood sash in the fully raised position
(so that the by-pass was effectively closed) two panels were
installed on both sides of the hood opening so as to leave the
center section clear. The open area was 50% of original full face.
Smoke and titanium swab tests were conducted at 690 CFM exhaust and
1035 CFM which represented 100 and 150 FPH control velocities
respectively. Pulsing and internal turbulence were significant at
both flows. At 100 FPM containment was generally satisfactory under
"good" room conditions but operator movement created momentary back-
flows and losses. Increasing flow to 150 did not improve condition.
3. One series of smoke tests were re-run using a biocabinet
with 10" sash opening that was totally exhausted (no interior recirc-
ulation) . The containment was very good at both 80 and 100 FPM
control velocity. The reduced vertical dimension (10" sash opening)
also minimized pedestrian traffic effect.
A copy of a previous study conducted on bio—containment cabinets
has been included in the appendix. The study notes the condition
and limitations on use of this type equipment.
-------
Conclusions:
A. General - The tests have verified the need for good laboratory
design if laboratory hoods are to provide the protection factors
desired and that there is no single control velocity that will
satisfy all conditions. Of prime interest also is that higher
velocities are not the answer.
THE OBVIOUS GOAL SHOULD BE TO PROVIDE THE MAYTMTTM OPERATOR
PROTECTION WITH THE MINIMUM QUANTITY OF AIR MOVEMENT. To accomplish
this for new facilities or a new project; the operations to be
controlled should be reviewed, the best location determined, and
then the hood or cabinet selected (based on performance).
If the review indicates that a 6 ft. long biocabinet, which is
operated with a sash height of 10" and an average face velocity of
100 FPM, will suffice then it should be used rather than a standard
fume hood. The cabinet would require approximately 500 CTM to
exhaust it while a six foot hood with a 32" sash height and 100 PPM
face velocity would require approximately 1500 CPM. Considered on
a yearly basis the energy savings would be tremendous.
B. New Laboratories - When hoods are required, location of hood
in area and make-up air systems should be selected that would create
"ideal" situation as described earlier. A face velocity of 80 FPM
should then be used as the design criteria for control. Whether
standard by-pass or auxiliary air hoods are selected should be based
on the economics of the required air conditioning equipment and
projected operating costs.
-------
C. P-ir-icting Laboratories - Where room conditions cannot be
rated "ideal" or "good", the room should be modified to up-grade
it to at least the "good" category before setting other laboratory
hood requirements. When "good" conditions are met, a face velocity
of 100 FPM should be used as the design control velocity.
The potential to up-grade existing hoods by adding a feature that
controls the pattern of air in the zone of the operator should be
considered.
D. To-^^ty of Material" and Hood Use - A good laboratory hood,
when selected, installed, and used as described, allows the worker
to handle a wide range of materials including those for which extremely
low TLV's have been developed. With extremely toxic materials for
which no lower safe limit is know, the concentration of the parent
material to be used and the operations involved should be thoroughly
reviewed by industrial hygiene personnel and others having expertise
in hazard control before containment equipment is selected. Some
operations such as weighing of concentrated mycotoxins for example
should be performed in a glove box or other total enclosure. Based
on "walk-thru" surveys of the 4 EPA sites, it was deemed that for the
operations being conducted and the materials handled, good laboratory
fume hoods would suffice in all but two areas observed.
VII. Hood Exhaust Systems;
A. General - Where possible, individual exhaust systems should be
provided for each fume hood. The combining of exhaust systems for
fume hoods located in the same laboratory where each user can see
and be aware of the other fume hood operations can be considered.
-------
Combining of systems beyond this should be strongly discouraged
because it increases the potential for many additional problems,
such as: difficulty in air balancing, loss of control at many
sites in case of fan failure, corrosive action, interference with
work of many operators during servicing or performing minor repairs
on system, reduced potential for adding effluent cleaning devices
in the future, and possible undesirable .interaction of effluents.
Supply air duct systems within the building can serve multiple
labs or hoods provided their design incorporates the necessary
damper requirements to assure hazard control ventilation is not
interfered with.
Duct material can vary but long-life-, corrosion resistance, and
accessibility for replacement are factors to be considered. Many
newer materials such as PVC are no longer price restrictive and
offer easy installation, on site welding, and experience with their
use has been good.
FANS SHOULD ALL BE AMCA RATED, AND SHOULD BE INSTALLED AT THE END
OF EACH DUCT SYSTEM SO THAI ALL DUCTS WITHIN THE BUILDING ABE
MAINTJLENED UNDER NEGATIVE PRESSURE.
Fan discharges should be angular-up into a vertical offset stack,
as shown in the ACGIH Industrial. Ventialation Manual (13th edition)
page 8-5, and the stack should extend at least 7 feet above roof level.
Fresh air inlets for the building supply systems should be displaced
as far as possible from the exhaust discharge.
-------
B. Effluent Cleaning - The dilution by hood exhaust air and
the the
the dispersion by vertical discharge foam/stack often negates/need
for effluent cleaning. This is not always true however and air
cleaning devices may be required. The type is determined by the
contaminant and degree of cleaning necessary, and can vary from
simple scrubbing and filtration units to incinerators or specially
designed units such, as a scrubber to be used for removing oxides
of nitrogen.
High efficiency particulate filters are now very common. These
units offer considerable resistance to flow even when filters are
clean and the resistance when "dirty" must also be considered as
part of system design and fan selection.
To maintain building air balance, keep laboratories under negative
pressure relative to surrounding areas, maintain proper hood control,
and extend filter life; it is recommended that a damper be installed
so that end resistance can be imposed initially and that the damper
be opened as filter gets dirty. This should be monitored by a
manometer installed across both the damper and the filter.
The filter plenum should be located on the inlet side of the fan
and be serviceable from the downstream (clean) side of the filter.
It is good practice to allow a straight run of duct prior to the
fan in order to obtain good fan performance as well as allow for
future installation of air cleaning equipment if necessary.
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VIII. Hood Surveillance and Hood Labeling Program;
A. General - To assure continued satisfactory performance, all
laboratory hoods should be inspected periodically. The initial survey
should be sufficiently extensive to properly rate the overall perform-
ance and provide a good baseline for follow-up inspections. The
frequency can be varied but all hoods should be inspected at least
once a year. If filters and dampers are involved or for any other
special applications, the inspections should be made at least once
every quarter.
B. Initial Test - This must determine "rating" of hood location
so all factors -tnri nrf-trig traffic and type of..inak&-.up air system must be
determined. Use of hood, person in charge, type of hood, fan data
including inlet and outlet static pressures, and RPM should be
recorded. Average face velocity should be determined (all readings
within 10Z of average), total flow should be determined and should
correlate with flow indicated by fan data or duct measurements.
Flow vectors should be checked using a titanium tetrachloride swab.
When satisfactory performance has been shown, the hood should be
labeled. A typical data card and labels are included in appendix.
C- Follow-up Inspections - Visual inspection should be made
to determine any changes which could effect performance and also
if hood use has changed. Face velocity and static pressure measurements
should be taken and recorded. If there is no significant change, label
date can be changed.
Any indication of change in control velocity should be investigated.
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APPENDIX
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Report of Tests Conducted on NCI Bio-Containment Cabinet (con't)
III
Test
No.
Tine of
Test Mins,
90
75
80
TABLE 1 (con't.)
Conditions of Test
Same as No. 3
Exhaust Volume Equal to
50 fpm face velocity &
recirculation on
(50 fpm)
Exhaust Volume enual to
fpm face Velocity &
Recirculation on 50 fpm
140
Result in percent of Cabinet
Concentration of Dranine
Detected
0.00122 at BZ-Operator
0.00082 at Lower Rt. Corner
0.0062 at BZ of operator
0.0012 at Lower Rt. Corner
0.0012 at BZ of Operator
0,00072 at Lower Rt. Corner
SERIES NO. 2 URANINE DYE introduced at Lower Cabinet — into inlet plenums for
recirculating fans. (Same as smoke tests discussed in introduction.) These tests
were conducted with exhaust volume set to provide 100 fpm average velocity through
sash opening with sash fully lowered to sash stops and with recirculating fan on.
Results in Table 2.
TABLE 2
Teat
No.
Time
Conditions of Test
Results in 2 Loss
85 mln.
80 rain.
100 fpm exhaust
Recirculation ON (50 fpm)
Same as #7
0.00352 at Front of Operator
0.0022 BZ Operator
0,00332 at Front of Operator
0.00172 BZ of Operator
SERIES NO. 3 — URANE DYE was Introduced into work area of Cabinet. Diffuser
pipe was a 1 inch copper pipe, 50 inches long, with a series of 1/16 inch holes on
1/2 inch centers along the entire length. The pipe was located in the upper front
of the cabinet work area, two inches down from the fcasa pad and 4 inches in from
the plane of the sash opening. Tests conducted under various conditions and results
are shown in table #3 below. The sash was fully lowered to sash stops.
TABLE 3
Test # Time (Mins.) Conditions of test Results 2 Loss
9 83 100 fpm average face ^0.00002 at front of Operator
velocity-Ho Recirculation 0.00002 at BZ of Operator
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Report of Tests Conducted on NCI iJio-Lontainment uuiuci -/
SERIES NO. A — USE OF SF6 GAS as test media. Gas Introduced through diffuser
pipe noted in series #3. The sash was fully lowered to sash stops.
TABLE A
TEST NO.
CONDITION OF TEST
RESULT IN % OF HOOD CONCENTRATION
AT POSITION NOTED
11
SF6 dispersed through
pipe —
100 fpa average face
velocity
No Recirculation
None detected (ND) Front of Operator
N,D. at Corners
N.D. at Lower arm of Operator
N.D. in General Room Air after 60 min.
run. Therefore all losses, based
on hood concentrations, were less
than 0.00002%
12
13
Sane as #11 but with
air recirculator ON
at 50 fpm down flov
50 fpm face velocity
50 fpm recirculation
velocity
Front of Operator 0.000122
Lower Arm of Operator 0,023
General Room after 72 minute run 0.0004%
Front of Operator 0.005%
Lower Arm of Operator 0,008!
General Room after 60 min. run 0.00035Z
GENERAL DISCUSSION:
All tests were conducted without external Interference and with the
mannequin in the sitting position as noted in Appendix A. The S76 samples were
of course spot samples but satisfactory agreement was obtained between long term
continuous sampling (uranine tests) and spot samples for SF6 over comparable
time intervals.
Smoke tests conducted illustrated that the recirculating air is drawn
towards the front of cabinet, and it would be subject to loss by outside
interference.
Zt was also noted that the perforated plate over the front trough has
sufficient resistance to air flow, that when removed the recirculating air flow
Increases significantly.
There are many parts of this unit that should not be exposed to
corrosive or highly flammable gasses or vapor.
There Is a need for a manometer or other device to indicate condition
of filters in recirculating system.
It should be noted that additional tests should be conducted with sash
fully opened and at varying recirculation rates. It was also noted that stops
prevented the sash from being closed, and the advantage of being able to close
the sash should be considered.
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Report of Tests Conducted on NCI Bio-Containment Cabinet (con't)
V
CONCLUSIONS;
1. This cabinet, if used in the total exhaust no recirculation mode,
could be used with toxic chemicals.
2. The use of the cabinet in the recirculation mode should be
limited to relatively non toxic particulates.
3. Use of highly corrosive liquids should be prohibited if any
spill potential exists.
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APPENDIS A
Performance Requirements for Bio-Containment Cabinets
General
A. All Bio-hazard Control Cabinets shall:
1. Be of the vertical laminar flow design*
2. Have vertical sliding sashes of 1/4" safety glass which operate
freely and provide a f«n open sash height of 24 inches.
3. Have stainless steel interiors, with work surfaces of the recessed
type.
4. Have flouresc en £ lighting capable of providing a minimum of 100
foot-candles at the work surface. Lights to be so mounted, that bolbs
are physically separated from the cabinet interiors, and lamp replacement
can be accomplished from the exterior of the unit.
5. Have a variable speed recirculating fan, with speed control device
exterior to the cabinet.
6. Have properly mounted HEPA filters (99.97Z efficient for 0.3 micron
particles) for cleaning both the air to be recirculated, and the air to
be exhausted.
7. Have aceess to fee up-stream side of the filters (for decontamination)
and the filters must be easily removed and replaced.
8. Have the recirculating fan discharge and the filter inlet within a
sealed plenum and this plenum, since it will be pressurized, must be as
small as practical.
9. Have an airflow indicating device that relates the condition of
the filters.
10; Be constructed so that all seams and joints are tight.
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5. After checking all joints for tightness, aerosol genera-
tion. will be started by turning on compressed air and
maintaining an IS" to 20" reading on the mercury manometer.
B. Air Sampling Procedure
1. Place a three-holed rubber stopper in the filter flask
and connect the vacuum pump to the aspirator leg of
the flask.
2. Place glass fiber filters in the filter holders (check
for tightness).
3. Place limiting orifices on outlet side of the filter
holders and connect them to holes in the stopper of the
filter flask. (Now all samples are manifolded and will
sample simultaneously when pump is turned on).
4. Turn pump on and check airflow through each sampler
using the rotameter. All flows must be identical.
(Actual flow not critical provided each sampler has
same flow rate).
5. Locate samplers in position for tests as described later.
6. Turn on aerosol generator.
7. Turn on sampling pump.
8. Sample for five minutes. Then shut off aerosol generator
and sampling pump.
9. Place exactly 50 ml of sodium carbonate solution in the
stoppered-shaking flasks.
10. Remove filters from the holders using tweezers, and
using caution to prevent contamination, place each
filter in a numbered shaking flask.
11. Stopper flask and shake vigorously for three minutes.
12. Filter a portion of the solution from each flask through
separate Whatman #41 filter papers and read fluorescence
in the fluorlmeter.
13. Make the necessary calculations.
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C. Check for Uniform Dispersion of Aerosol in Supply Air.
Three simultaneous air samples shall be taken at points across the
auxiliary air discharge and these samples when analyzed must indicate
that the uranine aerosol is uniformly distributed in the auxiliary air.
D. Check for Uniform Dispersion of Aerosol in Exhaust Air.
Three air samples shall then be taken in the exhaust duct at a point
as close to the hood exhaust collar as possible (not more than 4 feet
from hood). These discharge samples shall also be taken simultan-
eously with the sampler inlets located in' the same plane and at the
center of equal areas in the cross sectional area of the exhaust duct.
These samples when taken and analyzed must indicate the uniform
mixing of auxiliary air and room air.
&. Actual Test for Percent Entralxzment.
When it has been proven that the uranine is properly dispersed
throughout the auxiliary air and that the auxiliary air and room
air are thoroughly mixed at the exhaust sampling point, the performance
test shall be performed. For this test two samplers, one at the
point of discharge of auxiliary air from the supply system and one
at the centerline of ¦ the hood exhaust ¦ duct at the point previously
checked shall be taken simultaneously. These samples when analyzed
must indicate that at least 95Z of the auxiliary air supplied is
entrained and exhausted. Test to be conducted with sash in fully
raised position.
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J. With Che exhaust system off, turn on auxiliary air system
and adjust the supply air volume to 70Z of the exhaust air volume.
The supply air volume shall be measured by a calibrated flow device.
K. Under conditions as outlined in paragraph J above, measure
the air velocity along a line 3" out from the face of the hood
and at a height equal to the bottom of the sash when the sash is
in a fully raised position. The velocity should not exceed 200 FTM
along this line.
L. Turn on the exhaust system and operate as described in
paragraph B; maintain supply air operation as outlined in paragraph J.
This will provide a 70-30 ratio of auxiliary air to room air being
exhausted by the hood.
M. Again traverse the hood face (sash fully raised) with a swab
dipped in titanium tetrachloride. The smoke pattern shall show
air flowing into the hood and that no back flow exists.
N. Faint a strip of titanium tetrachloride along the sides and
working surface 6" back from the hood face. All air flow shall be
towards rear of hood with no back flow permitted.
0. Introduce a one-minute smoke bonds into the auxiliary air,
system prior to the point that air enters the plenum and observe
the air pattern. Smoke must indicate a smooth uniform air pattern
leaving the auxiliary air discharge and smoke must be efficiently
entrained and exhausted by the hood when the sash is fully raised.
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P. Repeat smoke bomb test as In paragraph 0, but with the sash
In fully closed position. Smoke must be efficiently captured by air
entering the bypass.
Q. Demonstrate that under the condition 702 auxiliary air supply
that capture of auxiliary air is at least 95Z efficient. Use the
uranlne dye test. Details of the test are described in paragraph 71.
R. Demonstrate that, under conditions wherein exhaust and supply
air volumes are equal, the loss of contaminated air from hood is less
than 0.Q5Z. Tests shall be as prescribed In paragraph VII.
S. Repeat tests in paragraphs Q and R but with auxiliary air
temperature maintained at 20°?. higher than the room air temperature.
UrarHne Dye Tes^for^^tr^^gr^-
A. Generation of Fine Uranlne Aerosol
1. Place approximately 8 cc of 5 to 10Z uranlne solution
into each of two nebulizers."
2. Set up the two nebulizers in parallel; connect air
hose from compressed air source and provide access
for the mercury manometer in the felr line (for
pressure reading).
3. Have both nebulizers discharge into the first of the
three settling flasks. Arrange for the aerosol to
leave the first flask and enter the second flask and
Chen to the third. (Flasks arranged in series). Each
Elask to be equipped with a tight fitting, two-hole
stopper having one long glass tube that extends close
co the bottom of the flask and one which is short and
extends just into the flask. The aerosol path should be
from the nebulizers Into each consecutive flask using
the long tube and exiting each flask by the short tube.
4. The exit tube of the last settling flask should be
connected by use of tubing to the point where the
aerosol is to be introduced into the supply air system.
This point must be upstream of the auxiliary air chamber
and preferably at the inlet to the supply air fan.
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I
INTRODUCTIONt-
The NCI Cabinet, as manufactured by Baker Company of Sanford,
Maine, was received early in April 1974. The cabinet was set-up in a
physically separate test area and connected to an exhaust system. This
system contains a calibrated orifice with a manometer readout for the
airflow range desired for the tests planned. However, the calibration
curve was rechecked at five (5) different airflows, using 20 noint pitot
traverses and this was done with the cabinet in place. Exhaust calibra-
tion check was satisfactory.
The recirculating fans within the cabinet were then set to
provide an average downward velocity, across the cabinet interior of
approximately 50 fpm. This was accomplished using a properly calibrated
Alnor Thermo-Anemometer and taking a total of 96 readings in a plane two
inches below the foam pad. The actual average velocity attained was 53
fpm and the high-low readings were 57 and 48 fpm respectively.
Initial testing was then instituted, with exhaust volume set to
provide an average face velocity of 100 fpm and recirculating fans set
as indicated (50 fpm downward velocity). A test gas, sulfur hexafluoride,
was then introduced into the recirculating air-flow by means of 'distribution
tube placed in the trough at the forward edge of the cabinet. The gas was
introduced at a flowrate of one liter per minute. Air samples were then
taken using a portable gas chromatograph equipped with a special column and
an electron capture detector. The unit has been calibrated and can easily
detect SF6 in concentrations of 0.5 PPB. These air samples, taken within
minutes, showed 5T6 is the Test Room air and definite leakage along the
upper airfoil particularly at the corners. At this point, gas tests were
discontinued.
A special manifold was then adapted to the lower cabinet so that
smoke could be Introduced beyond the absolute filters and Into the Inlet
plenum for each of the recirculating fans. Smoke Introduced in this
manner could be seen leaking from the cabinet in the area near the upper
corners of the air foil. This smoke test was repeated several times, and
leakage was obvious each tine. It was felt that this not only confirmed
the lntltal gas test but Indicated that these leaks were due to construc-
tion flaws. Arraneements were made throueh Mr. T.R. Wilkenson. Chief of
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Report of Tests Conducted on NCI Bio-Containment Cabinet (con't.)
Engineering & Sanitation Section, Environmental Services Branch, N.I.H., to have
a meeting in Cambridge, Mass., to demonstrate the problems encountered. This
meeting was held the last week of May and was attended by T.K. Wilkenson,
E. Barkley, F. Noble, and three representatives of the Baker Company.
Smoke tests were repeated, to visually demonstrate losses. The unit was then
partially dismantled and all agreed that several seams, particularly in the
pressurized return plenum, needed to be welded or otherwise sealed. Baker rep-
resentatives further agreed to properly seal unit so further tests could be
conducted. This was accomplished within a few davs and several smoke tests re-
vealed no visual losses from these sources. The planned series of tests were
then started.
SERIES NO. 1 — URANTNE DYE TEST, using aerosol dispersing unit located so that
the discharge was do&award and the forward edge of discharge opening was 6 Inches
in from the plane of the sash opening and at the same level, as the bottom edge of
sash, when sash was fully lowered to sash stops and located midway between the
cabinet sides.
This test was used initially since a similar test had been included as
part of a performance specification for cabinets evaluated recently. A copy of
the entire performance specification noted has been included as Appendix A for
reference purposes. The exhaust volume required for that test provided an
average velocity of 80 fpm through the face opening while 100 fpra was provided
initially for this cabinet test. Tests vere conducted with exhaust only (80 fpm)
same exhaust flow but with recirculation "on" (50 fpm average downward velocity),
exhaust volume equal to 50 fpm average face velocity with same recirculation as
noted and at exhaust to provide 140 fpm average face velocity with same recircula-
tion as noted. Results of these tests are included in Table 1 below.
TABLE 1
Test
No.
Time of
Test Wins,
60
3
75
75
Conditions of Test
100Z exh.—80 fpm face Velocity
and No Recirculation
Same as Test No. 1
Exhaust Volume equal to 80 fpm
face velocity & recirculation
on (50 fpm downward velocity)
Result In percent of
Cabinet Concentration
of Uranlne detected
None Detected»at Operator1
Breathing Zone—{0.00002%
None detected at Operator
Chest Level
None Detected—^0.00002Z
At Right Corner
None Detected ^0.00002%
None detected at same
locations ^0.00002%
0.00112 at BZ-operator
0.0008% at Lower Rt. Cornc
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9 - Beakers - Clamps
5 - Sing stands
12 - One minute smoke bombs
1 - Bottle Titanium Tetrachloride
1 - Box cotton swabs
1 — Pitot tube and inclined manometer (0-2"0)
1 - Alitor Thermoanemometer - type 8500 or equivalent with
recent calibration sheet
1 - Alnor Velometer - type 3002 or equivalent with recent
calibration sheet.
All necessary and associated glassware, rubber tubing
and miscellaneous items.
V. Performance Test Procedures:
A. Before any hood tests are conducted, or air systems for the
hood are turned on, demonstrate that no cross drafts exist in the test
area which exceed 20 FPM. Use the Alnor thermoanemometer for this
check.
B. Turn the exhaust fan on. Set the exhaust air volume to
provide an average face velocity of 100 PPM. The exhaust volume
shall be determined by using a device calibrated by proper pitot
tube traverses.
C. The uniformity of the face air velocity shall be determined
by taking velocity readings in the center of a grid made up of
three sections across the midd3 e third of the hood face across
the top third of the hood face, as well as three sections across
the lower third of the hood face. Readings shall not vary more
than plus or minus 10 FPM from average face velocity with the hood
sash fully raised.
0. Using a swab dipped in titanium tetrachloride, traverse the
hood face to show flow patterns of air entering the hood. No back
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flows shall be permitted.
E. Discharge a one-minute smoke bomb within the hood chamber
at workbench level. Proper and quick removal of smoke must be
demonstrated.
F. Lover the sash to a point six inches above the work surface.
Velocity as measured at three points across the reduced face opening
shall be at least two times but less than three times the design
face velocity when the sash was fully raised.
6. With the sash still at the lowered position, the exhaust
air volume (as indicated by the calibrated flow device) shall he
essentially the same as when the sash is fully raised. Now lower
sash to fully closed position. Total exhaust flow shall be
essentially as measured previously with different sash opening
positions.
H. Install the auxiliary air plenum and connect it to the supply
air system. The installation shall indicate relative ease of
adapting unit to the basic hood. No cutting or removal of exhaust
duct work shall be allowed.
£. Raise the hood sash and verify that the sash does not enter
the auxiliary chamber and that there is no appreciable opening
or means by which auxiliary air can enter hood either behind the
sash or through the bypass until the sash is lowered to the point
of bypass opening.
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IV. Performance Testing - General Requirements:
A. The fume hood shall be free of backdrafts along the bottom
and sides of the hood, and shall contain and carry away fumes
generated "within the hood when tested under conditions that will
simulate actual operating conditions as described herein. When
the hood is operated under the selected entrainment test conditions
as described, the hood shall capture at least 95Z of the auxiliary
air. When operated under the imbalance test conditions described,
the hood loss shall not exceed 0-052. The hood sash shall operate
smoothly and freely. Compliance to these performance requirements
shall, be demonstrated by conducting the series of tests as described
hereinafter. The owner and/or his designated representative shall
view the tests and successful compliance results are contingent
upon concurrence by the owner and/or his representative. All tests
shall be conducted prior to acceptance. Failure to meet
the performance requirements .may be cause for rejection of the
supplier.
B. A Test Room of proper design, all materials and equipment
required, as well as the actual test demonstrations shall be pro-
vided by the manufacturer at his own expense.
C. The Facilities Required shall include:
1. A typical bypass fume hood as specified (but without
auxiliary air plenum attached) shall be set up in a
test room of sufficient size so that TirtTTtTTnim of 5
feet of clear space is available in front of and on
both sides of the hood for viewing of performance tests.
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2. The test room shall have adequate heating and/or air
conditioning provided so that room air temperatures
can be maintained within ranges specified in perform-
ance specifications.
3. Room air currents and personal movement is front of
the test hood shall be properly controlled so that
air velocities shall not exceed 20 FFH in the test
viewing area.
A. A hood exhaust system, properly calibrated so that
known exhaust air volumes can be easily attained,
shall be provided.
5. An auxiliary air plenum complete with as inlet duct
stub shall be available for installation as required
in performance test procedure.
6. An auxiliary air system capable of supplying air through
the auxiliary air plenum is volumes up to 75Z of Che
hood exhaust volume shall be provided. This auxiliary
air system shall also be properly calibrated so that
airflows can be easily and accurately attained. The
auxiliary air system should have a heating unit capable
of maintaining the supply air temperature at any specified
temperature up to 95° F.
D. The materials Instrumentation and equipment required shall
include:
11 - #40 DeVilbiss Nebulizers
1 - Liter of 5% sodium carbonate solution
50 - cc of 5 to 10Z uranine in 51 sodium carbonate solution
3 - Gelman 47 mm filter holders (dosed) or equivalent
1 - Box Gelman 47 mm glass fiber filters Type A' or equivalent
3 - Glass probes (for sampling in exhaust duct)
1 - Vacuum Pump (Gelman Little Giant model or equivalent)
1 - Source of compressed air
1 - Mercury Manometer (0-25"Hg)
1 - Flowmeter (Rotameter) for flow rates of 2-10 liters/minute
3 - Settling Flasks (5 liter capacity or larger)
1 - Filter Flask (aspirator type)
3 - Limiting Orifices for sampling lines (6 liter/minute) suggested
3 - Filtering Funnels
1 - Box Whatman #41 filter paper (11 cm size)
3 - 50 cc stoppered shaking flasks
1 - Turner fluorlmeter or equivalent with proper filters and
curvettes
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L. Partial End Panels, removable, shall be provided at the
exterior ends of hoods to facilitate piping, wiring, and installation.
M. Electrical Switch(as), receptacle(s), and built in ground
fault interruptors shall be provided per schedules for the project
or as specified elsewhere.
N. Hood Working Surface shall be' 1-1/4" thick molded epoxy
resin (or other material as specified) made in the form of a water-
tight pan, not less than 3/8" deep to contain spillage. The raised
surface shall be provided all around the recessed pan area and it
shall be 2" wide across the front edge.
0. An Auxiliary Air chamber shall be located forward and above
the sash opening. The chamber shall be of modular design such that
it may be removed from the hood without dismantling the exhaust
duct or other potentially contaminated parts. The chamber, when
connected to a supply air system, shall direct a flow of auxiliary
air down the exterior front of the hood to be drawn through the
face opening (with sash open), together with the room air, by
the exhaust system. Hoods shall, provide efficient fume removal
when operating with up to 75Z of the exhaust air requirement being
auxiliary air and 25Z room air, when auxiliary air is supplied
at temperatures ranging from 70°F. to 90°?. The flow of auxiliary
air shall be confined to the area immediately in front of the hood,
and shall be entrained in the flow of air entering the hood with a
capture efficiency of at least 95Z. The hood sash shall never enter
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or travel through any portion of the auxiliary air chamber. The
interior, potentially contaminated back side of the sash shall never
enter the clean auxiliary air stream. The design of the air plenum
shall be such that it will accommodate the inlet duct to the plenum
from the top, front, or rear as indicated on drawings without
affecting the efficient performance of the unit.
P. Whan two speed exhaust fan systems are used, the micro
switch which will control both the supply air and exhausting air
fans shall be actuated by hood sash only. The micro switches shall
be so located that when the exhaust fan is on low speed, the design
volume of air is still exhausted from the room while maintaining
the design velocity.
III. Dimensions:
A. The superstructure outside dimensions, with auxiliary air
chamber, for bench-mounted fume hoods shall not exceed 78" in height,
36" in depth, 48", 60" 72", or 96" in length as selected.
B. Double wall end panel thickness shall not exceed 4".
C. Interior clear working height shall be not less than 47"
from the interior of the lintel panel to face of the baffle plenum.
D. sash opening •fwi"d*fg space below bottom air foil shall
be not less than 32" in height.
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coated cast bronze panel flange and angle serrated hose connector.
Interior fittings for steam shall consist of a cast bronze panel
flange and angle serrated hose connector with a chemical resistant
metallic bronze finish. Vertical facia shall be punched to receive
four remote control service fixtures at each side of the hood. Holes
not used for specific services shall be provided with removable plug
bottons. Cup drains will be positioned so as to allow direct water
flow from serrated waterlines.
G. A Two-Tube Fluorescent Light Fixture (bulbs not included)
of the longest practical length (up to 4 feet) shall be provided at
the top of the hoods. The light: fixture shall be hinged for relamping
and shall be shielded from the hood interior by a tempered glass panel
sealed into the hood body by an extruded vinyl channel.
H. A Vertical Sliding Sash shall be provided for the hoods
unless otherwise specified. Glass used in the sash shall be a minimum
of 7/32" thick combination sheet. The sash shall be composed of 18
gauge painted steel rolled shape, 3/4" thick x 2-1/2" wide, which is
mitered, welded and ground smooth at the corners to provide a complete
frame with no visible joints. Internal glass retaining strips shall
be rigid vinyl extrusions which interlock with the outer member to
retain the glass. Glass shall be sealed into the frame with an
extruded vinyl channel. The sash shall be counterbalanced with two
sash weights suspended one from each end of the sash by stainless
steel cables operating over ball bearing sheaves. The sash frame shall
be equipped with plastic guides, which operate in stainless steel sash
guides to insure proper operation of the sash and prevent metal-to-metal
contact.
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I. Hood'Interior Lining shall be Asbestos Cement unless
otherwise specified. The end panels, back panel, baffle and top
panels shall be not less than 1/4" thick, and shall be screwed
together with cleats or steel angles to form a completely rigid
assembly to which the exterior cold rolled steel parts can be mounted,
and to prevent open spaces or joints. The screws used to assemble
the interior end panels and mount the removable baffle shall be
stainless steel truss head screws, which are not countersunk, in
order to provide maTi-mra strength to the screwed joints. A rectangular
exhaust outlet of the size specified, constructed of type 304 stain-
less steel, extending 2" above the cement asbestos top panel, shall
be provided in the top of the hood in the plenum chamber area behind
the upper sloping baffle. The rectangular exhaust outlet shall, be
sized for approximately 1700 FPJI air velocity based upon a design
hood face velocity of 100 IPM.
J. A Sash Enclosure, shall be provided at the top of the hood
to receive the vertical'sliding sash when it Is in the UP position.
If required, the sash enclosure shall contain two removable panels -
one each on the front and rear surfaces - for access to the fluorescent
lighting fixture for relamping and cleaning. If project specifications
require Internal wiring to a central junction box, access to the
junction box shall be through the removable, gasketed panels.
K. Removable, Flush, Cement Asbestos Panels shall be provided
in both interior end panels to provide access to service piping and
valves to facilitate installation and maintenance.
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B. An airfoil, which presents a streamlined appearance similar
to the sides, shall be installed at the bottom of the hood opening.
TMg foil shall be mounted with approximately a one-inch open
space between the foil and the top front edge of the working surface
to direct an air stream across the hopd work top to prevent any
back flow of air at this point. The airfoil shall extend back
under the sash so that the sash closes on top of the foil and thus
does not close the approximate one-inch opening.
C. An Automatic Air Bypass shall be furnished for the hoods at
the top of the sash opening. This air bypass shall limit the maximum
air velocity through the face of the hood and provide a relatively
constant volume of air through the hood (regardless of sash position)
when the hood exhaust blower is in operation. The hood air bypass
shall not be dependent on mechanical or electrical linkage and shall
be completely positive in operation. The bypass shall be located
above the hood face opening, just forward of the sash when it is in
the raised position. The bypass shaU/provide an effective sight-
tight barrier between the area outside the hood and the hood interior.
The bypass shall also provide an effective barrier capable of controlling
transfer of flying debris from inside the hood. The bypass shall
control the increase in face velocity as the sash is lowered to attain
at least twice but not more than three times design face velocity.
D. A Removable Baffle, with one fixed non-adjustable opening
and two adjustable openings - one upper and one lower- shall be
furnished at the rear of the hoods. The adjustable baffle openings
-------
are to be provided to allow the flow of air through the hood to be
adjusted to compensate for types of gases, apparatus, or heat sources
used in the hoods.
E. Hood Exteriors shall be constructed of cold rolled steel
and shall have the component parts screwed together to allow the
removal of the end panels, front vertical facia pieces, bypass
grille, and airfoil to allow replacements or to afford access to
the plumbing lines and fixtures. Spacers or reinforcements shall
be welded to these main parts. After fabrication of all cold rolled
steel parts, but before final assembly, component parts shall be
given an acid, alkali,and solvent resistant finish on both exterior
and interior surfaces.
F. Hood Services shall consist of a cup drain flush with the
recessed working surface^plumbing,and electrical services as speci-
fied. Plumbing services shall consist of remote controlled valves
located within the double wall end panels, controlled by hexagonal
brass extension rods and handles projecting through the vertical
airfoils of the hood. Unless otherwise specified, the four-arm
handles shall be black add resistant, non-metallic plastic and
shall be furnished with tamper-proof and vandal resistant color
coded service indexes. Valves shall be connected to panel flanges
and angle serrated hose connectors located on the end panels within
the hood. Interior fittings for gases and water shall be integral
panel flanges and angle serrated hose connectors of acid resistant
plastic, color coded to match the service. Interior fittings for
distilled water shall consist of a tin lined, white epoxy
-------
2. Paint a strip of titanium tetrachloride along each end
and across the working surface of the hood, in a line
parallel with the hood face and 6" back into the hood
to demonstrate that no back flows of air exist at these
points. The flow of smoke shall be directly to the
rear of the hood without swirling turbulence or reverse
flows.
3. A smoke bomb (one-half minute size, as available from
E. Vernon Hill Company, San Fransico, California)
shall be discharged within the hood area to show the
exhaust capability of the hood and its design efficiency.
No reverse air flows will be permitted. Place lighted
bomb in the hood area and move it to various places,
meanwhile checking end panels and working surface to
verify that no reverse air flows exist at any point.
Lower the sash to closed position to verify that a
sufficient air volume is flowing through the hood
working area to carry away ftunes from a massive fume
source. Immediately after the smoke bomb stops dis-
charging smoke, the hood area shall be purged of smoke.
D. Lower sash to a point six inches above work surface. Velocity,
as measured at three points across the reduced face opening, shall be
at least two times but less than three times the design face velocity
when the sash was fully raised.
E. With, the sash still at the lowered position, the exhaust
air volume (as indicated by the calibrated flow device) shall be
essentially the same as when the sash was fully raised. Now lower
sash to fully closed position and measure exhaust flow. Total
exhaust flow shall be essentially as measured previously with the
different sash opening positions.
F. Check sash operation by raising and lowering sash. Sash
shall gi ^ d«» smoothly and freely and hold at any height without
creeping, assuring proper counterbalance. No metal-to-metal contact
shall be allowed between the sash and the sash track.
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AUTTT.TAgT ATR sm?PLIED LABORATORY FUHE HOOD SPECIFICATIONS
AND PERFORMANCE testing requirements
General Design:
at i fume hoods shall be of airfoil design with radiused foil
sections at the bottom and sides of the hood opening to insure
TnaT-tTmrm operating efficiency and minimum eddying of air currents.
They shall .be the "by pass" type to provide a relatively constant
exhaust air volume through, the hood (regardless of sash position).
Fume hoods shall be designed with an auxiliary air attachment
that will allow the use of up to 75Z auxiliary air. The design
of the auxiliary air attachment shall be such that all of the
auxiliary air shall enter through the hood face when Che sash
is in the open position and through the bypass into the hood
interior with the sash closed. Any design that introduces the
auxiliary air directly into the hood interior, behind the hood
face, regardless of sash position, will not be acceptable.
Construction;
A. Double Wall End Panels, not more than 4" wide, shall be
provided for *11 Fume Hood Superstructures, with the front of the
panel at the hood opening radlused, providing a streamlined section
and insuring a smooth, even flow of air into the hood. The hood
interior end panels shall be flush with the entrance shape to
prevent eddy currents and back flow of air. The area between
the double wall ends shall be closed to house the sash counter-
balance weight and remote control valves as are required.
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IV. Performance Testing - General Requlrpmpnts:
A. The fume hood when properly installed in a laboratory and
connected to an exhaust fan of the proper capacity, shall contain
and remove fumes generated within the hood. The face velocity
range shall be between 80-100 FPM as selected. The hood shall oper-
ate efficiently at any setting within this range. Hood design shall
be such that it will exhaust light or heavy gases efficiently when
the hood is used for ordinary laboratory work in a room free from
cross drafts and without high thermal loads or other special condi-
tions of this nature. No reverse flows of air will be allowed along
the sides, top, bottom, or front of the hood. All tests shall be
conducted prior to acceptance. The owner and/or his designated
representative shall view the tests and successful compliance results
are contingent upon concurrence by the owner and/or his representative.
Failure to meet the performance requirements may be cause for rejec-
tion of the supplier.
B. A test room of proper design and demonstration tests including
test materials and equipment shall be provided by the manufacturer at
his own expense.
C. The following instrumentation, equipment and supplies shall be
on hand for use in the performance tests:
1. ATnor "Velometer" or approved equal, direct reading, with
graduations from 0-350 ft./minute.
2. Pitot tube and inclined manometer with graduations no
greater than 0.02".
'3. One-half minute smoke bombs (3 dozen).
4. Titanium Tetrachloride (A ounces).
5. Supply of cotton throat swabs.
6. A variable volume exhaust system with a calibrated
flow device.
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V. Performance Test Procedures;
A. "Properly installed" means that the hood shall be installed
in an area vhere there is at least 5 feet clear space in front and
on each side for observation of the airflow pattern entering the
hood. This area shall be without cross drafts or other air currents
exceeding 20 TPM that would affect the hood performance in the area
in front and around the hood. Exhaust air volume shall be variable
to show hood operation at different face velocities within the
specification range.
B. Fume hood face velocities shall be verified as follows:
with exhaust .fan on, the quantity of air being exhausted shall be
determined by measuring the velocity of air entering the hood face
and multiplying this velocity by the square feet of hood opening.
The hood sash shall be in the fully raised position. The air
velocity shall be determined by averaging at least nine velocity
readings taken at the hood face. Readings shall be taken in the
center of a grid made up of 3 sections across the middle of the
hood face and 3 sections each across the bottom and top of the hood face.
Readings shall not vary more than + 10 FPH from the average face
velocity.
C. When the selected face velocity has been established, the
following tests shall be made:
1. Make a complete traverse of the hood face with a cotton
swab dipped in titanium tetrachloride to demonstrate a
positive flow of air is maintained into the hood over the
entire hood face. No reverse air flows or dead air
space shall be permitted.
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with an extruded vinyl* channel. The sash shall be counterbalanced
with two sash weights suspended one from each end of the sash by
*
stainless steel cables operating over ball bearing sheaves. The sash
frame shall be equipped with plastic guides, which operate in stain-
less steel sash guides to insure proper operation of the sash and
prevent metal-co-metal contact.
I. Hood Interior Lining shall be Asbestos Cement unless other-
wise specified. The end panels, back panel, baffle and top panels
shall be not less than 1/4" thick, and shall be screwed together
with cleats or steel angles to form a completely rigid assembly to
which the exterior cold rolled steel parts can be mounted and to
prevent open spaces or joints. The screws used to assemble the
interior end panels and mount the removable baffle shall be stain-
less, steel truss head screws which axe not countersunk in order to
provide maximum strength to the screwed joints. A rectangular
exhaust outlet of the size specified, constructed of type 304 stain-
less steel, extending 2" above the cement asbestos top panel, shall
be provided in the top of the hood in the plenum chamber area
behind the upper sloping baffle. The rectangular exhaust outlet
shall be sized for approximately 1700 FPU air velocity based upon
a design hood face velocity of 100 FPU.
J. A Sash Enclosure shall be provided at the top of the hood
to receive the vertical sliding sash when it is in the UP position.
K. Removable, Flush, Cement Asbestos Panels shall be provided
in both interior end panels to provide access to service piping and
valves to facilitate installation and maintenance.
-------
L. Partial End Panels, removable, shall be provided at the
exterior ends of hoods to facilitate piping, wiring and installation.
M. Electrical Svitch(es), receptacle(s), and built in ground
fault interruptors, shall be provided per schedules for the project
or as specified elsewhere.
N. Hood Working Surface shall be 1-1/4" thick molded epoxy
resin (or other material as specified) made in the form of a water-
tight pan, not less than 3/8" deep to contain spillage. The raised
surface shall be provided all around the recessed pan area, and it
shall, be 2" wide across the front edge.
HI. Dim<*nsions:
A. The supersturcture outside dimensions for bench mounted
fume hoods shall not exceed 65" in height, 36" in depth, 48",
60", 72", or 96" In length as selected.
B. Double wall end panel thickness shal1 not exceed 4".
C. Interior clear working height shall be not less than 47"
from the interior of the lintel panel to face of the baffle plenum.
D. Tftg sash opening including space below bottom air foil
shall be not less than 32" in height.
-------
D. A Removable Baffle, with one fixed non-adjustable opening
and two adjustable openings — one upper and one lover - snail be
furnished at the rear of the hoods. The adjustable baffle openings
are to be provided, to allow the flow of air through the hood to be
adjusted to compensate for types of gases, apparatus, or heat
sources used in the hoods.
E. Hood Exteriors shall be constructed of cold rolled steel
and shall have the component parts screwed together to allow the
removal of the end panels, front vertical facia pieces, by-pass
grille,and airfoil to allow replacements or to afford access to
the plumbing lines and fixtures. Spacers or reinforcements shall
be welded, to these main parts. After fabrication of all cold rolled
steel parts, but before final assembly, component parts shall be
given an acid, alkali, and solvent resistant finish on both exterior
and interior surfaces.
F. Hood Services shall consist of a cup drain flush with the
recessed working surface and plumbing and electrical services as
specified. Plumbing services shall consist of remote controlled
valves located within the double wall end panels, controlled by
hexagonal brass extension rods and handles projecting through the
vertical airfoils of the hood. Unless otherwise specified, the
four-arm handles shall be black acid resistant, non-metallic plastic
and shall be furnished with tamper-proof and vandal resistant color
coded service indexes. Valves shall be connected to panel flanges
and angle serrated hose connectors located on the end panels within
the hood. Interior fittings for gases and water shall be integral
-------
panel flanges and angle serrated hose connectors of acid resistant
plastic, color coded to match the service. Cup drains will be
positioned so as to allow direct waterflow from serrated water lines.
Interior fittings for distilled water shall consist of a tin lined,
white epoxy coated cast bronze panel flange and angle serrated hose
connector.' Interior fittings for steam shall consist of a cast
bronze panel flange and angle serrated hose connector with a chemical
resistant metallic bronze finish. Vertical facia shall be punched
to receive four remote control service fixtures at each side of
the hood. Holes not used for specific services shall be provided
with removable plug buttons.
G. A Two-Tube Fluorescent Light Fixture (bulbs not included)
of the longest practical length (up to 4 feet) shall be provided
at the top of the hoods. The light fixture shall be hinged for
relaaping and shall be shielded from the hood interior by a
tempered glass panel sealed Into the hood body by an extruded vinyl
channel.
H. A Vertical Sliding Sash shall be provided for the hoods
unless otherwise specified. Glass used in the sash shall be 7/32"
combination sheet. The sash shall be composed of a minlnnnn
of IS gauge painted steel rolled shape, 3/4" thick x 2-1/2 wide,
which is mitered, welded and ground smooth at the corners to provide
a complete frame with no visible joints. Internal glass retaining
strips shall be rigid vinyl extrusions which interlock with the outer
member to retain the glass. Glass shall be sealed into the frame
-------
STANDARD LABORATORY FUME HOOD S.ECIFICATIONS
AND PERFORMANCE TESTING REQUIREMENTS
General Design:
All fume hoods shall be of ai.rfoi.L~ design with radiused foil
sections at the bottom and sides of the hood opening to insure
¦maiHmrm operating efficiency and eddying of air currents.
They shall be the "by-pass" type to provide a relatively constant
exhaust air volume through the hood (regardless of sash position).
Fume hoods shall be so designed that, without modification, at
some future date an auxiliary air attachment can be added that
will allow the use of up to 70Z auxiliary air. Such auxiliary
air attachment to be mounted forward and above the sash opening
and designed such that all of the auxiliary air shall enter
through the hood face when the sash is in the open position and
through the by-pass into the hood interior with the sash closed.
Any design that introduces the auxiliary air directly into the
hood interior, behind the hood face, when the sash is in the
open position, will not be acceptable.
Construction:
A. Double Wall End Panels, not more than 4" wide, shall be
provided for all Fume Hood Superstructures, with the front of the
panel at the hood opening radiused, providing a streamlined section
and insuring a smooth, even flow of air into the hood. The hood
interior end panels shall be flush with the entrance shape to
prevent eddy currents and back flow of air. The area between
-------
the double wall ends shall be closed to house the sash counter-
balance weight and remote control valves as are required.
B. An airfoil - which presents a streamlined appearance similar
to the sides, shall be installed at the bottom of the hood opening.
This foil shall be mounted with approximately a one-inch open space
between the foil and the top front edge of the working surface to
direct an air stream across the hood work top to prevent any back
flow of air at this point. The airfoil shall extend back under
the sash, so that the sash closes on top of the foil, and thus
does not close the approximate one-inch opening.
C. An Automatic Air By-pas a shall be furnished for the hoods at
the top of the sash opening. This air by-pass shall limit, the
marlTmnn air velocity through the face of the hood and provide a
relatively constant volume of air through the hood (regardless of
sash position) when hood exhaust blower is in operation. The hood
air by-pass shall not be dependent on nwrhan-fcat or electrical
linkage, and shall be completely positive in operation. The by-pass
shall, be located above the hood face opening, just forward of the
sash when it is in the raised position. The by-pass shall provide
an effective sight-tight barrier between the area outside the hood
and the hood interior. The by-pass shall also"provide an~effective ~
barrier capable of controlling transfer of flying debris from inside
the hood. The by-pass shall control the increase in face velocity
as the sash is lowered to attain at least twice out not more than
three times design face velocity.
-------
-------
REPORT ON THE AERODYNAMIC PERFORMANCE OF
A CLEAN AIR SAFETY CABINET UNDER VARIOUS
MODES OF OPERATION
WORK SPONSORED BY: NATIONAL INSTITUTES
OF HEALTH
ORDER NO. PD-244674-4
DATED 2-15-74
WORK PERIOD: April 15 to August 1, 1974
DATE OF REPORT: ¦ August 12, 1974
STUDIES CONDUCTED BY:
RICHARD I. CHAMBERLIN
JOSEPH E. LEAHY
STEPHEN K. PICCOLO
Room 20-B-245 M.I.T.
77 Mass. Ave.
Cambridge, Mass., 02139
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Glossary of Terms
Air Vector
Back Baffle
By Pass
- The direction of the air flow.
- A rear partition which has two adjustable slQts
and one fixed slot.
- The opening which allows air to enter the hood
when the sash is closed.
Face Opening of Hood - The opening bounded by the two side airfoils,
countertop and the bottom of the sash.
Face Velocity
Plenum
Pulsing
Boiling Effect
- The velocity of air passing through the face
of hood.
- A pressure equalizing chamber.
- Not a steady state. Frequent movement of air
in different directions.
- The movement of air in the top section of the
hood which rolls around above the bottom of
the sash when the sash is in a raised position.
Uranine
- Sodium fluorescein
-------
-------
VII. Hood Loss Test Under Imbalance Conditions:
A. General: The imbalance test is a simulation of a possible
field condition which can be experienced when the exhaust system for
an auxiliary air hood exhausts less than the proper amount of air.
The reason for such reduced exhaust could be fan belt slippage, fan
blade corrosion, and other such commonly encountered problems. To
assure adequate and safe performance, the following test requires
that the auxiliary air hood when operated so that the exhaust air
volume has been reduced to equal the supply air volume, the loss
does not exceed 0.05Z of the hood concentration.
B. Test Procedure:
- Set auxiliary air volume.(using calibrated flow device)
to 702 of the exhaust air volume required to provide
an average face velocity of 100 FPH.
Set auxiliary air temperature so that it is essentially
equal to room air temperature.
Set exhaust air volume (using calibrated flow device)
the same as the auxiliary air volume in (1) above.
This provides condition of essentially 100Z supply.
Generate heavy concentration, of uranine aerosol within
the hood work area by setting up at least 9 of the #40
DeVilbliss Nebulizers filled with 10Z uranine and each
connected to a source of compressed air. Each of the
nebulizers should be provided with a goose-neck attach-
ment which deflects and impinges the aerosol generated
onto the bottom of an adjacent beaker. All nebulizers
and beakers should be located in a plane 6" back from
the hood sash opening, and equally space in that plane.
Using the manifolded sampling technique as *descrlbed
in 'VI^Bobtain the following three samples simultan-
eously. Sample No. 1 taken at the centerline of the
hood exhaust duct (represents hood concentration).
Samples No. 2 and 3 taken 6" in from each side of
sash opening, 12" out from plane of sash opening and
6" below level of work surface. The sampling time to
be at least sixty minutes in duration.
2.
3.
4.
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6. The samples shall Chen be extracted and fluorescence
determined as described in paragraph'71-2', steps 9
through 13.
7- Calculations must indicate that the hood loss under
imbalance conditions does not exceed 0.052 of the
hood concentration..
-------
BYPASS
Vs
SASH
SIDE AIR FOIL-r
BOTTOM
"AIR FOIL
RECESSED TOP
SASH PARTIALLY OPEN
SASH CLOSED
SFT.TinN SHOWING BYPASS-SASH AND AIR FOILS
-------
LI
PLAN VIEW
CALIBRATED OR'"*C
.CEILING OtFFUSER
PERFORATED PLATE
LOCATION
AUXILARY A)fc SUPPLY CHAfc'BCn
DUST STOP FJLTERS
STANDARD BYPASS*
HOOD
HOOD
2-3lx6' SLJD/NG D0OR5
SECTION A-A
i AYOIIT of testroom showing hood location
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402.258.25 INDUSTRIAL RELATIONS TITLE 8
(R*giif*r 7*. No. 33—
(j) Personal Protection.
(1) All employees required to work in such a manner that an? part
of their person may be wet, splashed or contaminated with liquids
other than water, shall be provided with appropriate protective
clothing and equipment as prescribed in S CAC, Article 10. Such
persons shall also be instructed as to hazards and safeguards of their
respective jobs as required in Section 5165(b), (c), and (d), and
Section 5162(c).
(2) Whenever liquids or chemicals harmful on contact to the skin
or eye tissues, or poisonous liquids or chemicals which can be ab-
sorbed through the slan, may splash or otherwise contact the em-
ployee's body, means of immediate rinse or dilution with clean water
shall be provided, as required in Section 3400, Medical Services and
First Aia and Section 5162, Corrosive Liquids, or as required in Sec-
tion 5166(b), (c), and (d), Poisons. (Title 24, T8-5I54(a), (b), (c),
(d). (e), (f). (0)
NOTB Authority cited: Section 142J. Labor Code.
History; L New section filed 7-l8»73; effective thirtieth day thereafter (Register 73,
No. 29).
Z. Amendments filed 7-16-T5; effective thirtieth day thereafter (Register 75,
No. 29).
5154.L Ventilation Requirements for Laboratory-Type ZIood Oper-
ations. (a) Definitions.
Hazardous Substance. One which by reason of being explosive,
flammable, poisonous, irritant; or otherwise harmful is likely to £ouse
injury.
Laboratory-Type Hood. A device enclosed except for necessary
exhaust purposes on three sides and top and bottom, designed to
draw air inward by means of mechanical ventilation, operated with
insertion of only the hands and arms of the user, and in which hazard-
ous substances are used.
(b) GeneraL When laboratory-type hoods are used to prevent
harmful exposure to hazardous substances, such hoods shall conform to
all applicable provisions of Article 107 and after January 1, 1978, shall
conform to provisions of this section.
(c) Ventilation Rates. Laboratory-type hood face velocities shall be
sufficient to maintain an inward flow of air at all openings into the hood
under operating conditions. The hood shall provide confinement of the
possible hazards and protection of the employees for the work which
is performed. The exhaust system shall provide an average face velocity
of at least 100 linear feet per minute with a minimum of 70 Ifm at any
point, except where more stringent special requirements are pre-
scribed in other sections of the General Industry Safety Orders, such as
Section 5209.
(d) Operation. Mechanical ventilation shall remain in operation at
all times when hoods are in use and for a sufficient time thereafter to
clear hoods of airborne hazardous substances. When mechanical venti-
lation is not in operation, hazardous substances in the hood shall be
covered or capped off.
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L_Ataur\M i wrv » ' - w "
BOTTOM AIR FOIL-
RECESSED TC'
EXHAUST DUCT
ADJUSTABLE TOP SLOT
FIXED
OPEN SLOT
-BYPASS
'/
;ide
\ FOIL
BACK BAF
PLENUM
7
ADJUSTABLE BOTTOM SLOT
-------
raised beyond the approved working height.
2« Be of the si2e and have the services as noted on Che working drawings.
Be wired and plumbed in accordance with OSIIA or other applicable codes.
*
Have a raised flange at exit of exhaust filter for accepting building duct,
erformance Testing Requirements
General:
1. The aerodynamic performance of all cabinets will be demonstrated by
esting in accordance with the test procedure outlined later in. this section or
>y an equivalent test procedure.
2. .The manufacturer will provide all necessary equipment including a
iroper test room, and will conduct the tests specified at his own expense. (Such
:ests to be conducted prior to award of contract).
3. The owner and or his representative shall view the tests and be sole
of compliance with said requirements.
Failure to meet the performance requirements as called for in the
ipecifications shall be justification for rejection of the bid and no further
.jnsideration shall be given to the bidder.
Testing Facilities
1. A typical bio-cabinet as proposed shall be set up in a test room of
sufficient size so that a minimum of 5 feet of clear space is available in front
if and on both sides of the unit for viewing of performance tests.
2. Room air currents and personal movement in front of the test hood shall
>e properly controlled so that air velocities shall not exceed 5 to 10 fpm in the
:est viewing area.
A cabinet exhaust system properly calibrated so that exhaust air volumes
:an be easily attained shall be provided.
-------
4. All of the testing equipment and materials as outlined in the
following paragraph shall be available -
10 - #40 DeVilbliss Nebulizers
1 - Liter of 5Z sodium carbonate solution
80 cc of 10Z uranine in 5Z sodium carbonate solution
3 - Gelman 47 am filter holders (closed) or equivalent
1 - Box Gelzsan 47 mm glass fiber filters Type 'A* or equivalent
1 - Vacuum pomp (Gelman Little Giant model or equivalent)
1 - Source of compressed air with pressure regulator
1 - Flowmeter (Rotameter) for flowrates of 2-10 liters /minute
1 - Aerosol generator consisting of a 10" x 10" battery jar equipped with
a cover. The cover to be adapted to accept ten impingement tubes equally
spaced about the periphery of the jar, with one outlet opening in the center
of cover. The Impingement tubes to be drawn from 1/2 inch glass and must -
project to within 1/2 inch of an impact plate placed on bottom of battery
jar. The nAtiizers shall then be attached to the Impingement tubes.
1 - Aerosol dispersing unit - consists of a 3" x 4" x 6™ high box. Top of
box fitted to accept aerosol from generator, through a 1" flexible plastic
Una. Two 24 mesh ..014" wire screens spaced 1" apart within box to dis-
tribute aerosol which then exits the box through a 1" x 4H slot, at forward
edge.
1 - Filter flask (aspirator type) with three holed stopper
3 - Limiting orifices for sampling lines (6 liter/minute) suggested
3 - Filtering funnels
1 - Box Whatman #41 filter paper (11cm size)
3 - 50 cc stoppered shaking flasks
1 - Turner fluorinetar or equivilent with proper filters and curvettes
1 - Mannequin
1 — Dozen, one minute smoke bombs
1 - Bottle titanium tetrachloride
1 - Box cotton swabs
1 - Pitot tube and Inclined manometer (0-2")
1 - Alnor thensoanemometer - type 8500 or equivilent with recent calibration sheet
1 - Alnor Velometer - type 3002 or equivilent with recent calibration sheet
ALL necessary and associated glassware, rubber tubing and miscellaneous items
-------
A. Before any tests are made demonstrate that no cross-drafts exist in
«
the test area which exc ed 10 fpm.
J. Set the sash to provide an 8" high face opening.
C. Turn the exhaust blover on. Set the exhaust air volume so as to
provide an average face velocity of 80 fpm. (Exhaust volume to be set using
a device calibrated by proper pitot tube traverses.)
D. Turn on recirculating fan. Adjust volume so that a minimum of 2-1/2
times the exhaust volume is being recirculated. Actual measurements to be made
in a plane parallel to and 15" above the work surface. (Use Alnor Thermoanemometer)
E. Using a svab dipped in titanium tetrachloride traverse the cabinet face
opening to show vector of *air entering cabinet. NO back-flows to be permitted.
F. Discharge a one-minute smoke bomb within cabinet and observe. NO leakage
allowed and quick removal of smoke must be demonstrated.
G. Demonstrate using uranine dye procedure as described in the following
Con or by any equivalent procedure that under the prescribed test conditions
the ratio of the concentration outside the cabinet is less than 2 x 10 ^ of the
concentration measured inside the cabinet (less than 0.000022! loss).
Uranine Dye Test to Measure Cabinet Containment
A. Generation of fine uranine dye aerosol.
1. Place approximately 8ce of 10Z uranine solution into each of the
10 nebulizers on uattery-jar unit (see description under aerosol
generator in list of required materials).
2. Place generator on work surface of cabinet.
The nebulizers must be connected i,n parallel to the compressed air
source.
3. Connect outlet of aerosol generator to inlet of aerosol dispersing
unit (see description in Section B.4 of materials required).
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4. Position aerosol dispersing unit so chat the discharge is downward
and the forward edge of discharge opening is 6 inches in from the plane
of the sash opening, at the same level as the bottom edge of sash (sash
open 8"), and located midway between the cabinet sides.
B Test Setup:
1. Place mannequin in position. Locate at center o£ cabinet with arms
projecting into work area.. Hands to be close to dispersing unit discharge.
2. Place a three-holed rubber stopper in the filter flask, and connect
the vacuum pump to the aspirator, leg of the flask.
3- Place glass fiber filters in the filter holders (check for tightness).
4. Place limiting orifices on outlet side of the filter holders and
connect to the holes in the filter flaske (Now all samplers are manifolded
and will sample simultaneously when pump is turned on.)
5* Turn pump on and check airflow through each sampler using the rotameter.
AU flows must be identical. (Actual flow not critical provided each sampler
has same flow rate.) Turn pump off.
6. Position Sampler 51 in hands of mannequin so that sampler inlet is
4W below bottom edge of sash, 6W in from the plane of the sash opening
and midway between the cabinet sides.
7. Position Sampler #2 directly in front of mannequin with sampler
inlet 4n below bottom edge of sash, 2" out from plane of sash opening
and midway between the sides of cabinet.
-------
8. Position Sampler #3 so Chat sampler inlet is two inches out from and
•jo inches belov the lower edge of the sash opening; and at a point two
inches in from either side of sash opening.
9. Turn on aerosol generator - (Maintain approximately 15 psi as measured
at source of compressed air).
10. Turn on Sampling Pump.
11. Sample for 90 minutes. Then shut off generaotr, sampling pump, and let
set for 5 minutes.
12. Place exactly 50 ml of sodium carbonate solution in the stoppered
shaking flasks.
13. Remove filters from the holders using tweezers; and using caution to
prevent contamination, place each filter in a numbered shaking flask.
14. Stopper flask and shake vigorously for three minutes or until filter is
thoroughly broken-up.
15. Filter a portion of the solution from each flask through seperate, pre-
washed and dried Whatman #41 filter papers, make dilutions as necessary, then
read fluorescence on Fluorimeter.
16• Hake the necessary calculations.
-------
/30
I ^
^ J/0
| *> V
3 I »
M"
V § "
^ ^
X AO
UXANINE AEROSOL DISPERSED 6" IN
FROM PLANE OF SASH & LEVEL WITH
BOTTOM OF SASH ffiDWAI BETWEEN
CABINET SIDES
FACE VELOCITY 80 F.P.H.
~ NO ~ ~
RFC/KCUl AT/CM
fi£C//?CULA T/O/
W/r/i
5~0/=./>/*7. Ool*WWA/
V&coc/ry
-------
COO
1 I
b I
I
o
\ N
0
? h
&SD
$00
J/fr
i/oo
3S0
300
250
2oo
/ro
JOO
6-0
BEAHINE AEROSOL DISPERSED 6" IN
FROM FLAKE 07 SASH I LEVEL RITE
BOTTOM OF SASH MIDWAY BETWEEN
CABINET SIDES
RECtROJLAIION AT SO FFM
DOHHHABD mOCITT
facf v/zoc/ry
-------
: .Hood No.
SUITABLE
For Work
With |
TOXIC Materials j
Ave. Vel 1 Jft./min. |
Industrial Hygiene ]
Office
Ext 2596
Date
Hood No..
For Work
With
TOXIC Materials
[ KEEP SASH BELOW
i- i i i i
t t t FT
Ave. Vei. 1 I R./min.
Industrial Hygiena
Office
Ext. 3*2596
Date
Hood No.
Air Velocity
NOT SUITABLE
For Work
With
TOXIC Materials
Ave. VeL
R./min.
industrial Hygiene
Office
Ext. 2596
Date
Hood No.,
Hood No..
REGISTERED
SUITABLE
For Worlc
With
RADIOACTIVE
Materials
Industrial Hygiene
Office
• Ext. 2596
Date
REGISTERED
For Work •
With
RADIOACTIVE
Materials
KEEP SASH BELOW
j I 1 I I
t t t t r
Ave. Vel. I 1 R./min.
Industrial Hygiene
Office
Ext. 3-2596
Date
Hood No.
NOT REGISTERED
i DO NOT USE
\ For Work
With
RADIOACTIVE
Materials
Industrial Hygiene
I Office
' Ext. 2596
Date
i
LABORATORY HOOD VENTILATION
oo wot shut ©ff
UNTIL LABORATORY SUPERVISORS
HAVE BEEN NOTIFIED AND HOODS IN
FOLLOWING ROOMS HAVE BEEN LABELED
NOTIFY E. M. S. EXT. 3-2596
J
-------
Boom Number
Department
Person i/c
Materials Used in Hood
How Operated
Switch Location
Other switches on system
Fan Location
Fan Identified
Other Hoods on this System
Dampers
Manual
Other
Filters
Type, manometer, tickled
Date:
Hood Number
Use of Room
Person Interviewed
Location of Hood in Room
Type of Hood
Fume cupboard
Sash
Vertical
Horizontal
Plenum No. of slots
By Pass
Supply Air percent
Work Surface
Material
Recessed
Interior Surface
Material
Recommended sash height
Labelled
-------
Boom Number
Department
Person i/c
Materials Used in Hood
How Operated
Switch Location
Other switches on system
Fan Location
Fan Identified
Other Hoods on this System
Dampers
Msmtta 1
Other
Filters
Type, manometer, tickled
uate:
Hood Number
Use of Room
Person Interviewed
Location of Hood in Room
Type of Hood
Fume cupboard
Sash
Vertical
Horizontal
Plenum No. of slots
By Pass
Supply Air percent
Work Surface
Material
Recessed
Interior Surface
Material
Recommended sash height
Labelled
Filter chgd:
Previous Filter chg:
Date:
Man. Rag:
_, . Name -
Filter: tvtia -
Name -
Pre Filter: Tvoe -
Damper Position:
RIM:
Man.- Rdg:
Damper Position:
Ave. Face Vel:
¦ Sash Hgt:
Ave. Face Vel:
Sash Hgt:
Sp across Filter:
inlet -
Outlet -
e .... Inlet -
Sp across Filter: o„M«r _
Date:
Man. Rdg:
Damper Position:
RIM:
Ave. Face Vel:
Sash Hgt:
Sp across Filter:
Inlet -
Date:
Man. Rde:
Damper Position:
RPM:
Ave. Face Vel:
Sash Ret:
Sp across Filter:
inlet -
Outlee -
Fan Data:
I1 "tie of Fan:
Model No.: Size:
Date:
Man. Rdg;
SL2e Motor:
RPM:
Damper Position:
RPM:
Sn: Inlet -
Outlet -
Ave. Face Vel:
Sash Hgt:
Sp across Filter:
Inlet •
Outlet -
-------
IX. Survey of Regulatory Agencies Present Standards:
ATI ten Occupation Safety and Health Adminstration (OSHA) Regional
Directors were asked for information as to standards their agency
recommends for design and operation of laboratory fume hoods and if
they have any face velocity requirements to meet OSHA Standards.
Seven answers were received and they all stated that OSHA did not
have a standard on design and operation of laboratory fume hoods
nor did they have specific face velocity requirements.
They stated the employees exposure would have to be evaluated- by
air sampling to determine OSHA compliance. For Che most part they
did make a reference to the "Ventilation Manual" published by the
American Conference of Governmental Industrial Hygienists. However
only errra stated that if an employees exposure was found excessive
by air sampling in his breathing zone then the face velocity of the
hood would be measured and if less than that recommended in the
"Ventilation Manual" they would use that to argue that engineering
controls were substandard.
A similar letter was sent to eight members of The Industrial Venti-
lation Committee of The American Conference of Governmental Industrial
Hygienists. The two answers received did not provide any useable
material.
Letters were also sent to 25 state agencies with 10 responses. Most
of these agencies would recommend the use of the Ventilation Manual
published by The American Conference of Governmental Industrial
Hygienists. The one exception was the state of California which as
of January 1, 1978'has a standard. A copy of which is is: the'appendix.
-------
SMOKE TEST - AJJX HOOD
701 SUPPLY - SHOWS CAPTURE
+ VOID FILLING
SMOKE TEST - AUX HOOD
SASH DOWN - AIR EI BY-PASS
HOOD ENTRAINMENT TEST
URANTNE
-------
HOOD LOSS TEST
IMBALANCE CONDITION
EQUIPMENT IN HOOD DURING TESTS
-------
HOOD LOSS - TRACER GAS
TEST SERIES 4-5-6
------- |