Where should return air not be taken from according to mechanical code standards?

Return air should not be taken from a hazardous or insanitary location because these areas can contain harmful contaminants, impurities, or pathogens that could compromise the indoor air quality of the building. The mechanical systems are designed to maintain a safe and healthy environment for occupants, and drawing air from areas that are unsafe or possess health risks goes against code standards meant to protect health and safety.

Places such as bathrooms, garages, kitchens, basements, boiler rooms, and attics may also have issues related to air quality or contaminants; however, the key distinction lies in the level of risk associated with those areas. For example, while air from a bathroom may contain moisture and odors, it typically does not present the same level of hazard as air from a hazardous or insanitary location. It's essential to ensure that the air being circulated through a building's HVAC system is as clean and safe as possible, focusing primarily on avoiding areas that inherently pose health risks.