What defines the breathing zone?

What defines the breathing zone?

• A. The space within 1 foot of the ceiling
• B. The zone immediately around the air supply diffuser
• C. The region 3 to 72 inches above floor and more than 2 feet from walls or fixed equipment
• D. The entire occupied space

Answer: (C)

The breathing zone is the air region where people actually inhale the air in a space. In ASHRAE 62.1 it’s defined as a vertical band extending from 3 inches above the floor up to 72 inches (6 feet) and located more than 2 feet away from walls or fixed equipment. This zone is used to assess the air people are exposed to, so measurements and ventilation performance should represent the air occupants breathe, not air that’s near ceilings, near direct supply jets, or air that’s heavily influenced by walls and obstructions. Near a diffuser, for example, the supply jet can create local flows that don’t reflect typical inhaled air, and the region within 1 foot of the ceiling is often stratified and not representative of breathing air. The entire occupied space includes areas outside the breathing zone where occupants don’t inhale air, so it isn’t the right focus for exposure.

The breathing zone is the air region where people actually inhale the air in a space. In ASHRAE 62.1 it’s defined as a vertical band extending from 3 inches above the floor up to 72 inches (6 feet) and located more than 2 feet away from walls or fixed equipment. This zone is used to assess the air people are exposed to, so measurements and ventilation performance should represent the air occupants breathe, not air that’s near ceilings, near direct supply jets, or air that’s heavily influenced by walls and obstructions. Near a diffuser, for example, the supply jet can create local flows that don’t reflect typical inhaled air, and the region within 1 foot of the ceiling is often stratified and not representative of breathing air. The entire occupied space includes areas outside the breathing zone where occupants don’t inhale air, so it isn’t the right focus for exposure.