The occupied zone is the region within a conditioned space where people work and spend time, typically extending 0.1 to 1.8 meters (4 to 6 feet) from the floor and 0.6 meters (2 feet) from walls and permanent fixtures. Ventilation design must prioritize air quality, temperature control, and air velocity within this zone. ASHRAE standards require ventilation system design to maintain acceptable conditions specifically in occupied zones rather than entire building volumes.
Dimensional Standards
ASHRAE 62.1 defines the occupied zone as a height between 0.1 and 1.8 meters above floor level, extending 0.6 meters from exterior walls and 0.3 meters from interior partitions. This definition ensures that ventilation requirements address the actual breathing and activity areas of occupants. Different room types have specific occupied zone boundaries; for example, standing work areas extend to 1.8 meters while seated workstations may be limited to 1.1 meters.
Design Applications
Occupied zone definition guides ventilation outlet placement, return-air grille positioning, and contaminant source location. Designers ensure supply registers deliver acceptable air velocity (typically 0.15-0.3 m/s at breathing height) without creating drafts. Thermal comfort requirements specify that temperature variation within the occupied zone not exceed 3°C between ceiling and floor. Proper occupied zone consideration reduces energy consumption by 20-30% compared to systems attempting to condition entire room volumes uniformly.