An outdoor air ventilation system consisting of a mechanical exhaust system, supply system or combination thereof shall be installed for _____ dwelling unit.

The requirement for an outdoor air ventilation system to be installed for each dwelling unit emphasizes the importance of ensuring that the indoor air quality is maintained at a safe and healthy level for occupants. Each dwelling unit functions independently and has its own unique air quality needs based on factors like occupancy, size, and usage. By mandating this system for every individual unit, it ensures adequate ventilation, proper moisture control, and the introduction of fresh air, which is crucial in preventing the buildup of harmful pollutants and maintaining comfort levels.

This specification aligns with established ventilation guidelines and codes that seek to promote occupant health and safety in residential environments. It differentiates from broader definitions or ambiguous wording that may imply a ventilation system might serve multiple units or select units, potentially compromising air quality standards in residential living spaces.