Exhaust Air

Exhaust air is the used, moisture-laden, or contaminated air that is extracted from a building and discharged outdoors. In a balanced ventilation system, exhaust air is drawn from rooms that generate the most moisture and pollutants — kitchens, bathrooms, WCs, saunas, and utility rooms — through dedicated exhaust vents connected to the air handling unit.

Proper exhaust ventilation is essential for removing excess moisture, cooking fumes, odors, and airborne contaminants from the home. Without adequate exhaust, humidity levels rise, leading to condensation on windows and cool surfaces, mold growth, and deterioration of building materials. In kitchens, insufficient exhaust allows grease particles and cooking odors to spread throughout the home.

Exhaust air vents and grilles should be cleaned regularly — at least every few months — to maintain design airflow rates. Grease and dust accumulate on vent covers and inside the duct openings, restricting airflow. A simple test is to hold a tissue near the exhaust vent; it should be pulled firmly against the grille. If it falls away, the airflow is insufficient.

In homes with mechanical exhaust only (no supply fans), the exhaust system creates slight negative pressure that draws makeup air through wall vents or window gaps. If doors slam shut on their own or you hear whistling sounds near windows, the negative pressure may be excessive and the ventilation system needs professional adjustment.