Prudent Practices in the Laboratory Handling and Disposal of Chemicals (1995) / Chapter Skim
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Laboratory Facilities
Laboratory Facilities
Pages 173-196
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From page 173... ...
.7 ... : Laboratory Facitities 8.A INTRODUCTION 8.B LABORATORY INSPECTION PROGRAMS 8.B.1 Items to Include in an Inspection Program 8.B.2 Types of Inspection Programs: Who Conducts Them and What They Offer 8.C LABORATORY VENTILATION 8.C.1 Laboratory Fume Hoods 8.C.2 Fume Hood Face Velocity 8.C.3 Factors That Affect Fume Hood Performance 8.C.3.1 Adjacency to Traffic 8.C.3.2 Adjacency to Supply Air Diffusers 8.C.3.3 Adjacency to Windows and Doors 8.C.4 General Safe Operating Procedures for Fume Hoods 8.C.4.1 Prevention of Intentional Release of Hazardous Substances into Fume Hoods 8.C.4.2 Fume Hood Performance Checks 8.C.4.3 Housekeeping 8.C.4.4 Sash Operation 8.C.4.5 Constant Operation of Fume Hoods 8.C.5 Testing and Verification 8.C.6 Fume Hood Design and Construction 8.C.6.1 General Design Recommendations 8.C.6.2 Special Design Features 8.C.6.3 Fume Hood Airflow Types 8.C.6.3.1 Constant Air Volume (CAY)
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From page 174... ...
174 PRUDENT PRACTICES IN THE LABORATORY: HANDLING AND DISPOSAL OF CHEMICALS 8.C.10 Other Local Exhaust Systems 8.C.10.1 Elephant Trunks 8.C.10.2 Slot Hoods 8.C.10.3 Canopy Hoods 8.C.10.4 Flammable-Liquid Storage Cabinets 8.C.ll General Laboratory Ventilation and Environmental Control Systems 8.C.ll.1 Supply Systems 8.C.11.2 Constant Air Volume 8.C.11.3 Variable Air Volume 8.C.12 Exhaust Systems 8.C.12.1 Individual Hood Fans 8.C.12.2 Manifolded (Common Header) Systems 8.C.12.3 Hybrid Exhaust Systems 8.C.12.4 Exhaust Stacks 8.D ROOM PRESSURE CONTROL SYSTEMS 8.E SPECIAL SYSTEMS 8.E.1 Glove Boxes 8.E.2 Clean Rooms 8.E.3 Environmental Rooms and Special Testing Laboratories 8.E.4 Biological Safety Cabinets and Biosafety Facilities 8.F MAINTENANCE OF VENTILATION SYSTEMS 190 190 190 190 191 191 192 192 192 192 192 193 193 193 193 194
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From page 175... ...
The large scale of some experiments may require special laboratory configurations and hazard containment measures; thus, these factors need careful consideration during the experimental design stage. Further, enhanced measures to protect laboratory workers from exposure to potential dangers, coupled with steps to conserve energy and minimize waste, have triggered the implementation of sophisticated systems to provide a safe, comfortable, and cost-effective work environment.
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From page 176... ...
Pay special attention to devices placed in fume hoods that do not meet National Electrical Safety Code (U.S.
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From page 177... ...
Facility engineers or maintenance personnel may add considerable value to safety inspection programs. It also gives them the opportunity to gain a better perspective on the laboratory work.
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From page 178... ...
C 3.2 Adjacency to Supply Air Diffusers Air is supplied continuously to laboratories to replace the air exhausted from the fume hoods and other exhaust sources and to provide ventilation and temperature/humidity control.
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From page 179... ...
· Do not modify fume hoods in any way that adversely affects the hood performance. This includes adding, removing, or changing any of the fume hood components, such as baffles, sashes, airfoils, liners, and exhaust connections.
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From page 180... ...
C 4.3 Housekeeping Laboratory fume hoods and adjacent work areas should be kept clean and free of debris at all times.
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From page 181... ...
, which exhaust the general laboratory air at a greater rate, both waste energy and are likely to degrade hood performance by creating air turbulence at the hood face and within the hood, causing vapors to spill out into the laboratory. Because a substantial amount of energy is required to supply tempered supply air to even a small hood, the use of hoods to store bottles of toxic or corrosive chemicals is a very wasteful practice, which can also, as noted above, seriously impair the effectiveness of the hood as a local ventilation device.
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From page 182... ...
Adjustable baffles can improve hood performance and are desirable if the adjustments are made by an experienced industrial hygienist, consultant, or hood technician. 8.C.6.3 Fume Hood Airflow Types The first fume hoods were simply boxes that were open on one side and connected to an exhaust duct.
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From page 183... ...
This does not mean that these fume hoods should not be closed when
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From page 184... ...
Varieties are available for horizontal sashes, but the bypass mechanisms are complicated and may cause maintenance problems. S.C.6.3.5 Auxiliary Air Hoods Quantitative tracer gas testing of many auxiliary air fume hoods has revealed that, even when adjusted properly and with the supply air properly conditioned, significantly higher worker exposure to the materials used in the hood may occur than with conventional (non-auxiliary air)
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From page 185... ...
8.C.6.3.6 Ductless Fume Hoods Ductless fume hoods are ventilated enclosures that have their own fan, which draws air out of the hood and through filters and ultimately recirculates it into the laboratory. The filters are designed to trap vapors generated in the hood and exhaust "clean" air back into the laboratory.
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From page 186... ...
~ . OX X TOP AIRFOIL SASH SIDE AIRFOIL /OTTO M / Al RFOIL \ _ I L BAFFLES \ 1 SASH FRAME ,l^/ FIGURE 8.4 Benchtop fume hood.
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From page 187... ...
The exhaust from a perchloric acid hood should not be manifolded with that from other types of fume hoods.
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From page 188... ...
They are also produced in a top mount version, in which the packing, spray manifold, and mist eliminator sections are located on top of the hood and the sump and liquid handling portion are underneath the hood for a compact arrangement taking up no more floor area than the hood itself. 8.C.8.3 Other Gas-Phase Filters There is another basic type of gas-phase filtration available for fume hoods in addition to liquid scrubbers.
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From page 189... ...
ll ~ I ~ ~~' DRAIN , . I ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ _ _ ~ 1 1 1 1 ~ 1 1 1 1 1 1 1 l l 1 1 ~ I ~ ~ an_ __ _` VALVE _ ~ ($ ~ ~(; ' ~ 1\ 1\~ \ \ \LEVEL CONTROLLER \ \pH CONTROLLER TDS CONTROLLER 8.C.8.4 Particulate Filters MIST ELIMINATOR SPRAY MANIFOLD F r ~ F ~ ~ f r ~ F ~ F _ ~ ~ ~ ~ ~ ~ ~ '^, ~ ~ ~ ~ ~ ~ ~ ~ ~ By_ ~ ~ _~ _% _% _% _% _% ~ _% _~' + ~ ~ ~` ~ ~ ~ ~ ~ ~ ~ l~ ~ ~ ,~, '~' - ~~% ~ Liquid Flow Air Flowed Or ,.%,,.~,.%,,.~,.~,.~,.~% PACKING 1 ~ SCRUBBING LIQUOR SUMP AIR , ~ FROM - : FUME J ~ HOOD Air from fume hoods and biological safety cabinets in which radioactive or biologically active materials are used should be properly filtered to remove these agents so that they are not released into the atmosphere.
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From page 190... ...
Also, their application to fume hoods has historically been rare. When considering this method of pollution control, an expert should be called to assist.
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From page 191... ...
Fires occur most frequently in fume hoods. Fire from a fume hood may propagate into a flammable-liquid storage cabinet directly vented into the hood.
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From page 192... ...
As the users operate the fume hoods, the exhaust volume from the laboratory changes and the supply air volume must adapt to maintain a volume balance and room pressure control. An experienced laboratory ventilation engineer must be consulted to design these systems, because the systems and controls are complex and must be designed, sized, and matched so they operate effectively together.
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From page 193... ...
C 1 2.3 Hybrid Exhaust Systems Certain types of fume hoods and exhaust sources, such as perchloric acid hoods, should not be manifolded with other types of fume hood exhausts.
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From page 194... ...
BSCs and other facilities in which viable organisms are handled require special construction and operating procedures to protect workers and the environment. Conventional laboratory fume hoods should never be used to contain biological hazards.
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From page 195... ...
Convenient sources of smoke for this purpose are the commercial smoke tubes available from local safety and laboratory supply companies. If the general laboratory ventilation is satisfactory, the movement of supply air from corridors and other diffusers into the laboratory and out through hoods and/or other exhaust sources should be relatively uniform.
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