What is prohibited regarding return air between dwelling units?

The prohibition regarding return air between dwelling units is based on the need to maintain indoor air quality and prevent cross-contamination between individual living spaces. When return air is discharged into another dwelling unit, it poses several risks, including the transfer of odors, allergens, or pollutants from one unit to another, which can lead to unhealthy living conditions. This practice can compromise the effectiveness of ventilation systems designed to provide clean, conditioned air and neutralize airborne contaminants.

Maintaining separate air pathways helps ensure that each dwelling unit maintains its own ambient air quality and regulations surrounding safety and health standards are met. In multi-family dwellings, systems are designed to respect the boundaries between units, and allowing return air to be shared can violate these standards. Ideally, the returned air should be re-circulated back to the same unit from which it originated, ensuring that any potential contaminants remain within that space, preserving the integrity of the air quality in each individual living area.