Laboratory Ventilation
Laboratories (and Flammable Storage Rooms) are classified as high-hazard areas; hazardous chemicals and processes are part of normal laboratory activities. In order to minimize hazards to laboratory workers and other building occupants, laboratories are designed, constructed, and managed differently than other types of occupied spaces. Multiple regulatory agencies are closely involved in the design/construction and inspection/permitting processes.
Laboratory design takes into account the activities conducted within the lab, and the materials used and stored in the lab. There are many built-in design elements that consider the usage of the lab (sprinklers; durable, chemical resistant surfaces, layout, plumbing, ventilation), particularly in modern labs. It is very challenging to retrofit a non-laboratory space into a laboratory space, and have code-compliant design and construction.
Laboratory ventilation is very different from ventilation systems found in other settings (e.g. office, classroom, residential, performance spaces, etc.). Due to the presence and use of hazardous materials, it is important that hazardous materials vapors do not accumulate in indoor spaces, where they present physical hazards (fire, explosion, energetic chemical reactions, corrosive action) and health hazards. As in any indoor space, air is supplied and exhausted; in laboratory spaces, air is never recirculated; it is 100% fresh Outside Air (OA) at all times. Laboratories are tremendous energy drains because of this, but it is required by building codes, the National Fire Prevention Association (NFPA), FDNY and OSHA.
Chemical fume hoods are the first line of defense against worker exposure to chemical vapors. When working with hazardous chemicals, always work in a properly operating chemical fume hood. Performance checks on fume hoods are done annually by EH&S personnel. You may also contact EH&S to request additional checks.
The chemical fume hood is a ventilated space within a lab that isolates the hazard (i.e. hazardous chemical vapors) from the worker, and removes the hazard from the indoor environment. The sash of the fume hood is lowered to increase the face velocity into the hood. The hood is always exhausting the same volume of air per unit time (Volumetric Flow Rate, in cubic feet per minute (cfm)), but the velocity at the opening of the hood (Face Velocity, in feet per minute (fpm)) is increased as the sash of the hood is lowered. The same volume of air per minute is moving through the smaller fume hood opening when the sash is lowered.
Chemical fume hoods are not left on at all times; turn the fume hood on before use. Fume hood fans are located on the roof of Davis and Science Hall; the fans cannot be heard while they are operating. Determine if the fan is on by checking the velocity monitor (Science Hall, new labs in Davis) or by holding a kimwipe up to the fume hood sash. Lower the sash to about 12 – 18 inches above the bench. At this height, hood will be at proper working face velocity and the sash will be at a height to block any splashes that might happen.
