Environmental Health and Safety
Laboratory Ventilation
Local ventilation consists of systems designed to remove the toxicant or contaminant from the point of generation, such as a chemical fume hood. General ventilation serves an entire work area supplying and removing air through diffusers or vents strategically located throughout a room. Many standards exist for proper design, maintenance, and operation of ventilation systems.
The OSHA’s Technical Guide recommends a face velocity of 80-120 feet per minute at a sash height of 18 inches for chemical fume hoods. Face velocity indicates the speed with which air moves into the hood interior. Fume hoods should be used for one of two purposes; either procedural use or storage, not both. Hood interiors should be kept free of objects that may impede airflow. Disruption of airflow may reduce the hood's ability to protect personnel. Face velocity is measured with an instrument called an anemometer or thermal anemometer. Face velocity measurements are the responsibility of EH&S and will be verified annually. In addition, smoke-inducing tubes should be used to verify proper airflow. Working sash height should be as low as practical. Biological safety cabinets are the subject of specific design and operating standards (National Sanitation Foundation Standard 49).
The Guide also recommends that air be supplied to laboratory rooms at a rate of 4 to 12 room changes per hour. General ventilation is important in maintaining employee comfort in the room and for removing low levels of contaminants that would be difficult to contain within a local exhaust hood. Contact EH&S if you suspect the general exhaust ventilation is insufficient.
Environmental Health and Safety can offer assistance with ventilation-related questions and concerns.
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