What is the primary function of an exhaust fan in a building?

The primary function of an exhaust fan in a building is to remove indoor air contaminants. Exhaust fans are designed to expel stale or contaminated air from areas such as kitchens, bathrooms, and laundry rooms, where humidity, odors, and various pollutants can accumulate. By removing this air, exhaust fans help improve indoor air quality, reduce the risk of mold and mildew formation, and enhance overall comfort for occupants.

While other functions, like circulating air or providing combustion air, are important in specific contexts, they do not capture the main role of exhaust fans. For instance, circulating heated air typically involves other systems, such as HVAC setups or ceiling fans, rather than dedicated exhaust fans. Similarly, providing combustion air is relevant in the context of appliances that require fuel combustion, but it is not the primary function of an exhaust fan. Increasing indoor humidity, on the other hand, contradicts the intended use of exhaust fans, which aim to reduce humidity levels by venting moist air outside. Therefore, the focus on removing indoor air contaminants distinctly supports the choice that identifies the main purpose of exhaust fans.