Mechanical ventilation systems must deliver outdoor airflow to which specific area within each occupiable space?

Mechanical ventilation systems are designed to ensure that the air delivered to indoor spaces meets the needs of the occupants in terms of quality and safety. The "breathing zone" refers to the area where people typically breathe, which is generally defined as being between 3 to 6 feet above the floor, where most occupational and recreational activities occur.

Delivering outdoor airflow specifically to this zone is critical because it helps to dilute indoor pollutants, maintain acceptable indoor air quality, and meet health guidelines that promote the well-being of occupants. The intention is to ensure that fresh air is effectively reaching those who are actively using the space, minimizing the risk of exposure to harmful contaminants that may accumulate closer to the ground or in stagnant air pockets.

In contrast, while common areas, storage areas, and hallways may also benefit from ventilation, they do not require the same specific focus on the breathing zone since those are not the principal areas of human activity where fresh outdoor air is most needed. Thus, the requirement to deliver outdoor air specifically to the breathing zone underscores the importance of protecting the health and comfort of individuals in any space where they might spend a significant amount of time.