What should ventilation air not be?

Ventilation air plays a crucial role in maintaining indoor air quality and ensuring that occupied spaces have sufficient fresh air. When considering what ventilation air should not be, recirculating the air can dilute the fresh air supply and potentially bring contaminants back into the space.

Recirculation implies that air is being reused without being exchanged for new air, which can lead to the buildup of indoor pollutants, odors, and moisture levels that are not sufficiently addressed. This can also compromise the efficiency of a ventilation system, especially if it's designed to introduce outdoor air to ensure proper ventilation rates.

On the other hand, exhausting ventilation air is necessary to remove stale air, filtered air is essential for protecting occupants from pollutants, and heated air can be required to maintain comfortable indoor temperatures during colder months. Thus, recirculating ventilation air is not an appropriate practice, as it undermines the very purpose of ventilation, which is to provide clean, fresh air while removing contaminants from the indoor environment.