General Laboratory Ventilation

Laboratory ventilation involves the use of supply and exhaust ventilation to control emissions, exposures, and chemical and biological hazards. A general lab ventilation system is designed to dilute and remove contaminants through general exhaust; provide make-up or replacement air, provide heating, cooling, and humidification; and provide local exhaust for specific activities. General ventilation does not eliminate exposure. Local exhaust is the preferred method for controlling exposures.

Ventilation Guidelines
Climate Controlled Spaces
Chemical Fume Hoods
Biosafety Cabinets
Local Exhaust and Containment Devices


General Ventilation

For a typical research laboratory, current ASHRAE standards recommend that there be 6-10 air changes per hour; in animal care holding areas, the National Research Council's "Guide for the Care and Use of Laboratory Animals" recommends 12-15 air changes per hour. The supply air introduced into the lab is provided by 100% fresh outdoor air. General ventilation dilutes contaminants and local exhaust (fume hoods) remove the contaminants. In the picture below, the supply and exhaust ventilation (general lab ventilation) dilutes the contaminants, while the chemical fume hood exhaust draws the contaminants out of the lab.

Labs should be pressurized so that contamination cannot escape from the lab into the hallways. A well-designed lab is under negative pressure to the hallway. In order to maintain that pressure and contain potential contaminants inside the lab, often times, the lab door must remain closed.

Fume hood sashes should be lowered when not in use.


Climate Controlled Spaces

Climate controlled spaces such as warm rooms and cold rooms usually do not have fresh air provided to them. Do not work or store hazardous materials in these spaces that could cause harmful vapors to build up. Liquid nitrogen tanks CANNOT be stored in these spaces due to the displacement of oxygen. When working in a climate controlled space, be aware of reactions or processes that may cause off-gassing of harmful vapors. These processes should be completed in a fume hood.


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