Fume hoods exhaust systems

The ventilation system in a laboratory using mercury or mercury compounds should conform to the general recommendation that wet chemistry laboratories involving any hazardous material be provided with 100% fresh air instead of having a portion of the air recirculated. Local ventilation systems, such as the exhausts of mechanical pumps servicing mercury diffusion pumps, should be collected with a local exhaust system and discharged into the fume hood exhaust system in the room or to a separate exhaust duct provided to service such units. The mercury vapor is much heavier than air so it is important that the room exhausts be placed near the floor or at the back of the workbench to collect as much of the vapors as possible. 

If a special-flammable storage cabinet ventilation system is installed, it should employ an AMCA-C type spark-resistant fan and an explosion-proof motor. Most fractional horsepower fans commonly used for this purpose do not meet this criterion and should not be used. If the building has a common fume hood exhaust system, then it is appropriate to hook a flammable-storage cabinet up to it if it must be ventilated. 

Paint and varnish manufacturing Resin manufacturing closed reaction vessel Varnish cooldng-open or closed vessels Solvent thinning Acrolein, other aldehydes and fatty acids (odors), phthalic anhydride (sublimed) Ketones, fatty acids, formic acids, acetic acid, glycerine, acrolein, other aldehydes, phenols and terpenes from tall oils, hydrogen sulfide, alkyl sulfide, butyl mercaptan, and thiofen (odors) Olefins, branched-chain aromatics and ketones (odors), solvents Exhaust systems with scrubbers and fume burners Exhaust system with scrubbers and fume burners close-fitting hoods required for open kettles Exhaust system with fume burners... 

Make sure that all highly toxic or offensive vapors are scrubbed or adsorbed before the exit gases are released into the hood exhaust system (see section 8.C.8.1 on fume hood scrubbers). 

Certain types of fume hoods and exhaust sources, such as perchloric acid hoods, should not be manifolded with other types of fume hood exhausts. In large buildings where the designer wishes to take advantage of the benefits of manifolded exhaust systems but wishes to isolate a few exhaust streams, a combination, or hybrid, of these two types of systems is usually the most prudent and cost-effective alternative. 

There must be enough air exchanges in the laboratory area, and laboratory air must not be recirculated to the supply system as makeup air that is, laboratory exhaust air must not be recirculated back into either the containment area or the rest of the building, even if the exhaust air is HEPA-filtered. Some regulations may require HEPA filtration of exhaust air from the facility regardless of the fact that it will not be recirculated. It is also necessary to determine the location and direction of the building s air and fume-hood exhaust dischai e to ascertain that the air intake will... 

Diazomethane. CA UTION. Diazomethane is highly toxic its pre paration should be carried out only in a fume cupboard (hood) provided with a powerful exhaust system. The use of a screen of safely glass is recommended. 

This latter equation can also be used for systems without a local exhaust hood by setting the capture efficiency to zero. It could also be used to show the result of recirculation from, e.g., a laboratory fume hood with immediate recirculation. In such a hood all contaminants are generated within the hood and usually also all generated contaminants are captured, so the capture efficiency is 1. The equation demonstrates that if the... 

Fume hoods must be of a type suitable for the service they are intended to perform. For many applications, minimum face velocity is specified by regulations. An installer should always check the velocity when a new hood is placed in operation. It should be rechecked whenever any modification is made to the exhaust system. It is up to the laboratory operator to make certain that a hood is not put to new uses for which it was not designed. 

Laboratory aisles must be no less than 5 feet wide and benches should have sufficient unobstructed width to accommodate modern analytical instrumentation. An overhead (filtered) exhaust system would permit small canopy hoods to be connected as necessary to scavenge fumes from areas near injection and exhaust ports of analyzers not located in hoods. Each room should have its own supply... 

Safety glasses must be worn in the laboratory at all times. Material safety and data sheets should be read prior to the start of the experiment. All chemicals should be considered hazardous from a standpoint of flammability and toxicity. Appropriate safety gloves must be worn when using organic solvents so that no skin contact is permitted. Care must be taken to use organic solvents either in a well-ventilated area or in a hood. Avoid breathing the fumes or sources of electrical sparks. The GPC instrument, including solvent reservoir and waste container, should be vented to a fume hood or other exhaust system. 

CAUTION For safety, the hydrogenation process should be carried out in a chemical fume hood, and the exit line should be placed so as to ensure that the waste gas is expelled through the hood s exhaust system. 

All exhaust from a mechanical pump should be vented to a fume hood regardless of the room s ventilation quality or the type of pumped gases. Each time you bring new samples into vacuum conditions, your system is pumping at atmospheric pressured Because pump oils have low vapor pressures, and pump oils themselves are considered nontoxic, there is little concern for breathing pump oil mist. However, there may be dangers from trapped vapors within the pump oils. Regardless, there is little reason to breathe the pump oil mist if it can be avoided. Check with the manufacturer or distributor of your pump for an oil mist filter for your pump. If you use a condensate trap, be sure you position your exhaust line so that material does not drain back into the pump (see Fig. 7.14). 

Caution The digestion should be conducted in a fume hood, or the digestion apparatus should be equipped with a fume exhaust system. 

PERSONAL PROTECTION wear NIOSH/MSHA-approved respirator, chemical-resistant gloves and other protective clothing use only in chemical fume hood avoid prolonged or repeated exposure wash thoroughly after each exposure use dust-proof safety goggles a system of local exhaust ventilation is recommended to control emissions at the source and to prevent dispersion into general work area use positive pressure self-contained breathing apparatus maintain eyewash fountains and quick-drench facilities in work area. 

This area also serves as the preliminary sample processing facility. It may contain muffle furnaces, drying ovens, grinding mills, evaporation bays, and fume hoods with dedicated exhaust lines. All exhaust from this area must be treated by pre-filters, HERA filters, and wet scrubbing prior to discharge to the environment. Each muffle furnace and drying oven must be covered with a canopy exhaust system to remove the heat and fumes generated from the heated samples. 

The laboratory shall be equipped with a fume hood. The fume hood should meet any specific safety requirements mandated by the nature of the research program. A discussion of hood design parameters will be found in a later section, but for high hazard use the interior of the hood and the exhaust duct should be chosen for maximum resistance to the reagents used the blower should either be explosion-proof or, as a minimum, have non-sparking fan blades the hood should be equipped with a velocity sensor and alarm should the face velocity fall below a safe limit the interior hghts should be explosion-proof, and all electrical outlets and controls should be external to the unit. It may be desirable to equip the unit with an internal automatic fire suppression system. 

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