1/6/2024 0 Comments Airflow system for labThe design depends upon the fume hood numbers, types, sizes, locations, diversity, etc. This is the principle around which fume hoods and laboratory air handling systems are designed. Also, if incoming CFM is too less the fume hood might starve of air to function effectively and drive out the contaminants. If the incoming CFM is more than the exhausted CFM, the lab will be under positive pressure which would mean the contaminants will remain trapped inside. Little less air, because we need the laboratory to be under negative pressure to drive out the contaminated air constantly. In any case, a little less volume rate (CFM) of air must enter the laboratory room by way of either through door/ window openings (non-AC lab) or forced flow through supply air ducts (AC labs). This is driven by system logic, the objective of which is to achieve air-conditioning cost reduction without compromising safety. For a variable air volume fume hood (VAV) the air volume rate varies, as per the sash movement. This is true for a constant air volume (CAV) fume hood. For example, if 100 feet per minute (fpm) is required and the hood has a sash opening of 7.5 square feet, then the hood’s air handling volume rate is 750 (7.5 x 100) cubic feet per minute (CFM). Air volume passing through a fume hood is generally equal to the area of the sash opening multiplied by the average velocity (face velocity) desired. It doesn’t work in isolation but depends on the overall laboratory room air availability and dynamics.Īirflow in the hood is achieved by an exhaust blower which pulls the air from the laboratory room into and through the hood and the exhaust system. The fume hood is essentially air handling equipment. A fume hood needs adequate airflow to remove, contain and safely discharge airborne chemical contaminants.
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