Fume Hood Performance Checks

Fume hoods and other associated protective equipment should be maintained in satisfactory operating condition at all times. Monitoring of performance and any scheduled preventive maintenance should be done in accordance with the manufacturers suggested guidance. The OSHA Laboratory Standard states that fume hoods need to have a hood velocity of 60 to 100 linear feet per minute to be considered as adequate. In order to ensure that lab fume hoods continue to meet this standard, the Safety Division performs quarterly fume hood inspections. Moreover, during each inspection fume hood velocity checked. For each hood inspected an individual inspection sheet is used and all entries resulting from the inspection must be made there. 

Periodic checks or tests of laboratory fume hood performance are important in protecting workers health. With normal use the hood s efflciency in containing or capturing contaminants may decrease for many reasons normal wear, loose component parts (e.g., fan belts), out-of-adjustment dampers, clogged air cleaners, and ductwork blocked by dust and debris. 

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. 

Caution Carry out all procedures in a well-ventilated fume-hood, wear appropriate disposable gloves, a lab-coat, and safety glasses. All vacuum-line work should be performed while standing behind a protective Perspex screen. Check all glassware for star cracks before use with any reduced pressure system. Never use flat-bottomed flasks with rotary evaporators. 

ASHRAE 110, Method of Checking Performance of Laboratory Fume Hoods, American Society of Heating, Refrigerating, and Air Conditioning Engineers, Fairfax, VA, 1995. 

Surveys for airborne activity are required for laboratories where radioiodine is used. The surveys should cover working areas and fume hood duct discharges. Check the efficiency of vapor entrainment at the fume hood face by collecting air samples from the operator s breathing zone using an activated charcoal sampling trap. Your radiation safety office can assist you or perform this service. 

It is important to keep in mind that even though the fume hood equipment might be performing up to standards it may still not provide enough protection for the user. The point is that no matter how well the unit checks or tests out, the system is not performing adequately if air samples show excessive employee exposures. One can only be sure that the hood system is providing sufficient protection if hood system tests can be correlated with air contaminant concentrations. 

Fume cupboards, slot captor or receptor hood ventilation. These must be driven by a suitable and adequate fan, and will often need water wash, dust filtration or precipitators built in. Local air pollution control requirements may require capture of vapours, which cannot simply be discharged fiom an exhaust vent. The ventilation system pressures should be checked regularly to spot obstmctions or reductions in fan performance, and the pressure figures recorded. 

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