Which space is prohibited from being the source of return air?

The prohibition of using a bathroom as a source for return air in HVAC systems is based on several important considerations related to air quality and comfort. Bathrooms typically contain higher levels of moisture, odors, and contaminants from personal hygiene products. If the return air system pulls air from bathrooms, it might not only carry these unpleasant odors and moisture throughout the home, but it can also affect the overall indoor air quality.

Additionally, using a bathroom as a return air source might lead to the entry of excess humidity into the HVAC system, potentially causing issues such as mold growth or deterioration of the ductwork.

In contrast, living rooms, dining rooms, and bedrooms are typically designed to be comfortable living spaces where the air quality is prioritized. They are more suitable for return air sources because they do not generally harbor the same level of moisture or unpleasant odors found in bathrooms, ensuring a healthier environment and better performance of the HVAC system.