Afkastluft

Afkastluft is the portion of indoor air that is expelled from a building by a ventilation system. It removes heat, moisture, odors and pollutants from rooms and helps maintain indoor air quality. The term is commonly used in Danish and Nordic HVAC contexts and is contrasted with tilførsel, or tilførselsluft, the air that is brought into the building.

In ventilation concepts, afkastluft may be processed in different ways. In exhaust ventilation, fans pull air out from spaces such as kitchens and bathrooms and discharge it outdoors. In balanced ventilation, afkastluft is part of a paired process with tilførselluft, so that the amount of air leaving roughly equals the amount entering, helping maintain pressure balance. Systems with varmegenvinding (heat recovery) use the energy from afkastluft to pre-warm or pre-cool the incoming tilførsel, increasing energy efficiency.

The composition and rate of afkastluft depend on occupancy and activities and are used to meet indoor air quality and comfort requirements. Airflow rates are typically specified in cubic meters per hour (m3/h) or air changes per hour (ACH). Duct and filter design influence the removal of moisture, odors and contaminants from the space before the air is exhausted.

Maintenance and safety: Regular inspection of exhaust outlets, ducts and fans is important to prevent blockages, backdrafts or mold growth. Proper separation of exhaust paths from air intakes and adherence to local regulations are essential for safety and comfort.