Fans, ducts, air cleaners, inlet and outlet grilles, sensors, and controllers are all components of a ventilation system. Exhaust ducts from hoods must not contain any fire dampers.
Negative pressure allows air to flow from the surrounding areas into the laboratory.
This prevents odors and contaminants from exiting the laboratory. Other than clean rooms air pressure in laboratories shall be negative with respect to corridors and non-laboratory areas. Exhaust air from the laboratory should not be recycled, but rather discharged to the outside. The exhaust stack must extend 10 feet from the highest point on the roof and be placed far from the fresh air intake vents for the comfort ventilation systems to ensure there will no entrainment of fume hood exhaust into building. Ventilation plays an important part in the proper performance of laboratory hoods, in particular the location of room ventilation systems in relation to the fume hoods.