The OR requires specialized criteria for the ventilation system as well. The surgical
area must be replenished with fresh air at regular time intervals time to maintain a safe
and sterile environment. A minimum of three air changes per hour of outdoor air, and 15
total air changes per hour, is required (AIA, 1996). A positive pressure must exist between
the operating room and adjacent areas, to prevent the inflow of contaminated air. The ventilation
system also should be designed so that there is no recirculation of air from room
to room.