Industrial Ventilation - Dilution Ventilation

Dilution ventilation is usually accomplished with the use of large exhaust fans in the walls or roof of a building or room. Opening doors or windows can be used as dilution ventilation, but this is not always a reliable method since air movement is not controlled. Cooling fans (floor fans) are also sometimes used as a method of ventilation, but these fans usually just blow the contaminant around the work area without effectively controlling it.

Dilution ventilation can be more effective if the exhaust fan is located close to exposed workers and the makeup air is located behind the worker so that contaminated air is drawn away from the worker's breathing zone. See Figure 1 for examples of best locations for exhaust fans and air inlets.



In cases where the source of contamination is widely scattered or is from a mobile source, like carbon monoxide from a forklift, large wall or roof exhaust fans can be effective. Makeup air to replace the air exhausted is necessary for the best control. Simple openings in walls or doors can be sources of makeup air, or a second fan can draw makeup air into the building or room. However, makeup air may require heating in the winter resulting in increased heating bills.