Where should return air not be sourced from according to the mechanical code?

Return air should not be sourced from hazardous or insanitary locations due to the potential health risks associated with contaminated air. The mechanical code emphasizes the importance of maintaining good indoor air quality, which can be severely impacted if return air is taken from areas that may contain pollutants, toxins, or biological contaminants. These hazardous locations can include areas with chemical storage, sewage systems, or any environment that may harbor harmful substances.

By disallowing return air from such locations, the code helps ensure that the air circulated throughout a building does not carry harmful particles or pathogens, thus protecting the health and safety of occupants. This regulation is foundational to promoting a safe and comfortable indoor environment, contributing to the overall effectiveness of the HVAC system in maintaining air quality.