Prudent Practices in the Laboratory Handling and Management of Chemical Hazards, Updated Version (2011) / Chapter Skim
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9 Laboratory Facilities
9 Laboratory Facilities
Pages 211-254
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From page 211... ...
9 Laboratory Facilities 9.A INTRODUCTION 213 9.B GENERAL LABORATORY DESIGN CONSIDERATIONS 213 9.B.1 Relationship Between Wet Laboratory Spaces and Other Spaces 213 9.B.1.1 Relationship Between Laboratory and Office Spaces 213 9.B.2 Open Laboratory Design 213 9.B.2.1 Considerations for Open Laboratory Design 213 9.B.3 Closed Laboratories and Access 214 9.B.4 Equivalent Linear Feet of Workspace 215 9.B.5 Laboratory Layout and Furnishing 215 9.B.5.1 Adaptability 215 9.B.5.2 Casework, Furnishings, and Fixtures 216 9.B.5.3 Shared Spaces 216 9.B.5.4 Flooring 216 9.B.5.5 Doors, Windows, and Walls 216 9.B.6 Noise and Vibration Issues 216 9.B.7 Safety Equipment and Utilities 217 9.B.8 Americans with Disability Act: Accessibility Issues Within the Laboratory 218 9.B.9 Older Facilities 218 9.C LABORATORY VENTILATION 219 9.C.1 Risk Assessment 219 9.C.2 Laboratory Chemical Hoods 221 9.C.2.1 Laboratory Chemical Hood Face Velocity 221 9.C.2.2 Factors That Affect Laboratory Chemical Hood Performance 222 9.C.2.3 Prevention of Intentional Release of Hazardous Substances into Chemical Hoods 222 9.C.2.4 Laboratory Chemical Hood Performance Checks 222 9.C.2.5 Housekeeping 223 9.C.2.6 Sash Operation 223 9.C.2.7 Constant Operation of Laboratory Chemical Hoods 224 9.C.2.8 Testing and Verification 224 9.C.2.9 Laboratory Chemical Hood Design and Construction 228 9.C.2.10 Laboratory Chemical Hood Configurations 231 9.C.2.11 Laboratory Chemical Hood Exhaust Treatment 234 9.C.3 Other Local Exhaust Systems 236 9.C.3.1 Elephant Trunks, Snorkels, or Extractors 237 9.C.3.2 Slot Hoods 237 9.C.3.3 Canopy Hoods 237 9.C.3.4 Downdraft Hoods 237 9.C.3.5 Clean Benches or Laminar Flow Hoods 239 9.C.3.6 Ventilated Balance Enclosures 239 9.C.3.7 Gas Cabinets 239 211
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From page 212... ...
Systems 241 9.C.5 Supply Systems 241 9.C.6 Exhaust Systems 241 9.C.6.1 Individual Laboratory Chemical Hood Fans 241 9.C.6.2 Manifolded (Common Header) Systems 241 9.C.6.3 Hybrid Exhaust Systems 242 9.C.6.4 Room Purge Systems 242 9.C.6.5 Exhaust Stacks 242 9.D ROOM PRESSURE CONTROL SYSTEMS 242 9.E SPECIAL SYSTEMS 243 9.E.1 Gloveboxes 243 9.E.2 Clean Rooms 243 9.E.2.1 Clean Room Classification 243 9.E.2.2 Clean Room Protocols 244 9.E.2.3 Laboratory Chemical Hoods and Laboratory Furniture in Clean Rooms 244 9.E.3 Environmental Rooms and Special Testing Laboratories 244 9.E.3.1 Alternatives to Environmental Rooms 245 9.E.4 Biological Safety Cabinets and Biosafety Facilities 245 9.E.4.1 Biosafety Cabinets 245 9.E.4.2 Using a Biosafety Cabinet for Biological Materials 247 9.E.5 Nanoparticles and Nanomaterials 247 9.E.6 Explosion-Proof Chemical Hoods 248 9.F MAINTENANCE OF VENTILATION SYSTEMS 248 9.G VENTILATION SYSTEM MANAGEMENT PROGRAM 249 9.G.1 Design Criteria 249 9.G.2 Training Program 249 9.G.3 Inspection and Maintenance 250 9.G.4 Goals Performance Measurement 250 9.G.5 Commissioning 250 9.H SAFETY AND SUSTAINABILITY 250 9.H.1 Low-Flow or High-Performance Laboratory Chemical Hoods 251 9.H.2 Automatic Sash Closers 251 9.H.3 Variable Air Volume (VAV)
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From page 213... ...
Laboratory person Locating all offices outside the laboratory environnel need to understand the capabilities and limitations ment allows for a safer workspace where food can be of the ventilation systems, environmental controls, consumed, quiet work can be done, and more paper laboratory chemical hoods, and other exhaust devices and books can be stored. Locating the office zone very associated with such equipment and how to use them close to or adjacent to the laboratory for easy access and properly.
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From page 214... ...
Design teams should work with the research teams In another laboratory, a container of nitric acid to find solutions that accommodate the needs of the and methanol sitting in a chemical fume hood researchers as much as possible. A combination of overpressurized and burst, spraying shards of open laboratory spaces with smaller areas dedicated glass and nitric acid over every surface of the to special functions is often necessary.
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From page 215... ...
This number includes the support length of laboratory chemical hoods. Equipment ELF space outside the laboratory that is needed.
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From page 216... ...
to floor tiles, because floor tiles may loosen or degrade Where interstitial spaces are not possible, overhead over time, particularly near laboratory chemical hoods service carriers may be hung from the underside of and sinks. Rubberized materials or flooring with a the structural floor system.
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drains near the units, preferably sloped to the drain to • Locate room purge buttons at the exits in laboraprevent excessive flooding and potential slip hazards. tories with chemical hoods.
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In addition, some school systems and municipalities require a minimum number or percentage of accessible work areas in teaching laboratories. Accessible furniture, including laboratory chemical hoods, are readily available from most suppliers.
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• overabundance of laboratory chemical hoods, • l aboratory chemical hoods with large bypass 9.C.1 Risk Assessment openings, • dampers in fixed positions, For all materials, the objective is to keep airborne • overventilated laboratory spaces, concentrations below established exposure limits (see • excessive duct pressure, Chapter 4, section 4.C.2.1)
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From page 220... ...
• Laboratory 10–15 air changes/minute or 60- Flammable, toxic, or reactive materials • chemical hoods 100 fpm depending on hood type Products or mixtures with uncharacterized hazards • Unventilated 0 air changes Flammable liquids • storage cabinets Corrosives • Moderately toxic chemicals • Highly toxic, hazardous, or odiferous chemicals (if equipped with flame Ventilated storage 1–2 air changes/minute cabinets arrestors) • Recirculating A1: 75 fpm Biological materials • biosafety cabinets A2: 100 fpm Nanoparticles, as of the date of publication • B1: 100 fpm Biological materials • Nanoparticles, as of the date of publication • Minute amounts of volatile chemicals • Total exhaust B2: 100 fpm Biological materials • biosafety cabinet Nanoparticles, as of the date of publication • Minute amounts of volatile chemicals • Glovebox Varies from no change to very Positive pressure for specialty environments • high rate of change, depending Negative pressure for highly toxic materials on the glovebox and the application • Downdraft table 150–250 fpm depending on Perfusions with paraformaldehyde, work with volatile, low to moderately design hazardous materials with higher vapor density where access from more than one side is necessary • Elephant trunk 150–200 fpm at opening Local ventilation of a tabletop • Discharge from equipment such as a gas chromatograph • Canopy N/A Ventilation of heat, steam, low or nontoxic materials with low vapor density • Ductless laboratory 10–15 air changes/minute Materials that are compatible with the filtration system, in controlled quantities chemical hood and under controlled conditions • Not suitable for particularly hazardous substances • Slot hood Varies with application Local ventilation of higher density materials at the source, such as an acid bath • Ventilated balance 5–10 air changes/minute Weighing and initial dissolution of highly toxic or potent materials enclosure • Benchtop ventilated Variable per the needs of the Benchtop equipment, such as rotovaps enclosures materials Vapor pressure is usually measured in millimeters material easily forms vapors and may require use of a of mercury.
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portional to the face velocity and there is no consistent evidence that the higher face velocity results in better containment. Face velocities approaching or exceeding 9.C.2 Laboratory Chemical Hoods 150 fpm should not be used; they may cause turbulence Laboratory chemical hoods are the most important around the periphery of the sash opening and actually components used to protect laboratory personnel reduce the capture efficiency, and may reentrain settled from exposure to hazardous chemicals and agents.
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9.C.2.2 Factors That Affect Laboratory Chemical 9.C.2.3 Prevention of Intentional Release of Hood Performance Hazardous Substances into Chemical Hoods Tracer gas containment testing of chemical hoods reveals that air currents impinging on the face at a ve- Laboratory chemical hoods should be regarded as locity exceeding 30 to 50% of the face velocity reduce safety devices that can contain and exhaust toxic, ofthe containment efficiency by causing turbulence and fensive, or flammable materials that form as a result interfering with the laminar flow of the air entering of laboratory procedures. Just as you should never the chemical hood.
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From page 223... ...
Keep laboratory chemical hoods and adjacent work • If possible, position the chemical hood sash so that areas clean and free of debris at all times. Keep solid work is performed by extending the arms under or objects and materials (such as paper)
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If the only way to keep the sash in a fully raised 9.C.2.7 Constant Operation of Laboratory position requires the use of a sash stop, the Chemical Hoods laboratory personnel may get into the habit of leaving the sash in this position, potentially Although turning laboratory chemical hoods off reducing the safety and energy efficiency of the when not in use saves energy, keeping them on at all chemical hood. times is safer, especially if they are connected directly • The standard operating position for the vertical to a single fan.
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From page 225... ...
It is highly recommended If the laboratory chemical hood and the general ventithat chemical hoods be retested by trained personnel lating system are properly designed, face velocities in after installation in their final location, using ANSI/ the range of the design criteria will provide a laminar ASHRAE 110-1995 or equivalent testing. The control flow of air over the work surface and sides of the hood.
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From page 226... ...
• Ensure that the laboratory chemical hood is being 9.C.2.8.4 ace Velocity Testing F used as intended (e.g., no evidence of perchloric acid in a chemical hood not designed for it, not Visually divide the face opening of a laboratory using it as a chemical storage device)
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From page 227... ...
However, one must understand how the average standard deviation of velocities at each tra- chemical hood will be used to determine the range of WITHOUT BAFFLES WITH BAFFLES Exhaust Exhaust Duct Duct Sash Sash Top Baffle Upper Airfoil Plane Of Plane Sash Of Sash Back Baffle Velocity Velocity Profile Profile Lower Airfoil Work Surface Work Surface Effect of baffles on face velocity profile in a laboratory chemical hood. FIGURE 9.4 Figure 9.4.eps
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When specifying a laboratory chemical hood for use When baffles are installed, the velocity distribution is in a particular activity, laboratory personnel should greatly improved. Adjustable baffles can improve hood be aware of the design features.
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is constant, the face velocity varies inversely with the Many trained laboratory personnel are reluctant to sash position. The laboratory chemical hood volume close their CAV nonbypass chemical hoods because of should be adjusted to achieve the proper face veloc- the increase in air velocity and noise that occurs when ity at the desired working height of the sash, and the the sash is lowered.
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9.C.2.9.3.3 Bypass Laboratory Chemical Hoods 9.C.2.9.3.4 Variable Air Volume Laboratory Chemical Hoods A bypass chemical hood is shown in Figure 9.6. It is similar to the nonbypass design but has an open- A VAV chemical hood, also known as a constant ing above the sash through which air may pass at low velocity hood, is one that has been fitted with a face sash positions.
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From page 231... ...
For example, if the chemi- limited conditions cited above and with rigorous filter cal hood is designed to meet performance criteria at a maintenance programs. They can also be used for consash height of 18 in., but users must operate it at a sash trol of particulate material where a chemical hood or height of 24 in., the hood may not be effective at 24 in., even Class 1 or 2 biosafety cabinets provide too much creating a potentially hazardous situation.
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From page 232... ...
Chem D filter media are working, and the filter maintenance ical Fume Hoods schedule. The distillation hood is similar to the benchtop hood except that the work surface is closer to the floor to 9.C.2.10 Laboratory Chemical Hood allow more vertical space inside for tall apparatuses Configurations such as distillation columns.
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It 9.C.2.10.5 erchloric Acid Laboratory Chemical P may include respirators, chemical splash goggles, rub- Hoods ber gloves, boots, suits, and self-contained breathing The perchloric acid laboratory chemical hood, with apparatus. A typical walk-in chemical hood is shown its associated ductwork, exhaust fan, and support in Figure 9.9.
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Special treatment of the exhaust 9.C.2.11 Laboratory Chemical Hood Exhaust from radioisotope hoods may be required by govern Treatment ment regulations to prevent the release of radioactive material into the environment. This treatment usually Until recently, treatment of laboratory chemical hood involves the use of HEPA filters (see section 9.C.4.2)
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experiments involving toxic materials should be de 9.C.2.11.2 iquid Scrubbers L signed so that they are collected in traps or scrubbers rather than released. If for some reason collection is A laboratory chemical hood scrubber is a laboratoryimpossible, HEPA filters are recommended for highly scale version of a typical packed-bed liquid scrubber toxic particulates.
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underneath for a compact arrangement taking up no 9.C.2.11.4 igh-Efficiency Filters H more floor area than the hood itself. Most hoods do not require a scrubber unit, assuming the exhaust stack is Air from laboratory chemical hoods and biologidesigned properly and chemical quantities of volatile cal safety cabinets (BSCs)
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Note that unless the intake for the snorkel is placed very close to the 9.C.3 Other Local Exhaust Systems point source, it will be susceptible to inefficient capture. Many types of laboratory equipment and apparatus Newer designs mount the intake on an articulated arm, that generate vapors and gases should not be used which tends to make the systems more effective and in a conventional laboratory chemical hood.
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238 PRUDENT PRACTICES IN THE LABORATORY Fume extractor or snorkel. FIGURE 9.11 Diagrams of typical slot hoods.
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These de 9.C.3.8 Flammable-Liquid Storage Cabinets vices are installed with different specifications for face velocity than the standard laboratory chemical hood Store flammable and combustible liquids only in and are well suited for locating sensitive balances that approved flammable-liquid storage cabinets, not in might be disturbed if placed in a laboratory chemical a chemical hood, on the bench, or in an unapproved hood. The average face velocity is specified at 75 fpm storage cabinet.
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If the building has the required rate. Computational fluid dynamics moda common laboratory chemical hood exhaust system, els are often utilized to determine minimal rates when hook a flammable-liquid storage cabinet up to it for the lab is occupied and unoccupied.
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As users operate the • There is no way to dilute the laboratory chemical chemical hoods, the exhaust volume from the labora- hood effluent before release. tory changes and the supply air volume must adapt to • Providing redundancy and emergency power for maintain a volume balance and room pressure control.
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From page 242... ...
Manifolded VAV systems also allow design engineers to take advantage of diversity. Simply stated, 9.C.6.3 Hybrid Exhaust Systems diversity is an estimate of the actual expected peak Certain types of laboratory chemical hoods and airflow rate expressed as a percentage of the total ex exhaust sources, such as perchloric acid hoods, should haust capacity.
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Consult a laboratory expert in clean room operation before a clean room is designed, built, 9.E SPECIAL SYSTEMS or worked in. 9.E.1 Gloveboxes 9.E.2.1 Clean Room Classification Unlike a chemical hood, gloveboxes are fully enclosed and are under negative or positive pressure.
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Thus, it is important to ensure that Laboratory chemical hoods and laboratory furniture hazardous materials are stored in ventilated cabinets in clean rooms must be easy to clean and not subject and work with volatile hazardous materials is done to rust or chalking. Most prefer not to use materials with proper ventilation.
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They use less electricity, take up much less space, and have just as 9.E.4 Biological Safety Cabinets and much control over the environment. Biosafety Facilities A shaker box is a sealed cabinet with a pull-out work BSCs are common containment and protection surface.
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Internal supply air passes through a HEPA filter in a downward laminar 9.E.4.1 Biosafety Cabinets flow across the work surface, preventing cross A biosafety cabinet is specially designed and con- contamination. It works by drawing room air structed to offer protection to the laboratory person- around laboratory personnel through slots in the nel and clean filtered air to the materials within the work surface at the front of the cabinet, offering workspace.
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Some Class II biosafety cabinets may be connected • Delay manipulation of materials for approxito the laboratory exhaust system and may be touted mately 1 minute after placing the hands/arms as a combination biosafety cabinet and chemical hood. inside the cabinet.
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HEPA filters into the room or those that are hard Though traditional chemical hoods may be used for ducted to the outdoors may provide good containresearch on nanoscale particles and materials, some ment for nanoparticles. Class II biosafety cabinets researchers find it challenging to work with nanopar- that exhaust air through HEPA filters back into ticles in hoods operating with a 100-fpm face velocity the room or those that are hard-ducted to the outbecause of turbulent airflow.
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For each exhaust port (e.g., system management program: design criteria, training laboratory chemical hoods) , the product of the face area for laboratory personnel, system maintenance, and (in square feet)
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From page 250... ...
elements of the inspection and maintenance program, All laboratory personnel should receive training that including includes • designation of who conducts inspections and how • how to use the ventilation equipment, often; • consequences of improper use, • how inspections are recorded; • what to do in the event of system failure, • inspection criteria for laboratory chemical hoods • what to do in the event of a power outage, including • special considerations or rules for the equipment, face velocity testing -- equipment used, history, • significance of signage and postings. how recorded, how posted on the chemical hood, and Training may be one-on-one, classroom, Web-based, will maximum sash height be marked and how; or whatever format fits the culture of the institution • criteria for working on roofs and around stacks; and the needs of the laboratory.
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Cost considerations should never take precedence over ensuring that laboratory personnel are protected 9.H.1 Low-Flow or High-Performance from hazardous concentrations of airborne toxic sub Laboratory Chemical Hoods stances. That sentiment bears repeating.
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From page 252... ...
An advantage of a VAV system is that individual chemical hoods or an entire system can be adjusted to 9.H.6 Laboratory Chemical Hood a setback mode, a low flow that maintains negative Alternatives pressure but conserves energy. The laboratory chemical hood is a fabulous engineer The setback mode may be activated in a number of ing control, but it is not the only one.
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communications between the users and the installers The assessment of radiological hazards is relatively and the maintenance staff to ensure that the systems straightforward and requires standard methods for are working as intended. handheld survey meters and wipe tests for removable Remember that even if all the chemical hoods are contamination.
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Sophisticated biological decontamination Residual perchloric acid and mercury contamination technologies are available for areas where high-risk are common concerns for laboratory decommissioning. pathogens have been used.
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