Air Pressure Requirements for OR Suite

Q: I have a small 28 bed hospital with one OR suite. Within the OR suite are sterile rooms, a soiled room, and of course the Operating Room, etc. We are rebalancing the air flows for the entire floor which is all health care occupancy. I am aware that the rooms mentioned above, all have air pressure relationship requirements to adjacent areas per the Guidelines for Design & Construction of Hospitals and ASHRAE 170. However, some are questioning the need to have a positive air pressure relationship between the OR suite and other areas. That is, they measure the pressure from the OR suite door to other side which is the in-patient corridor. Is there any pressure relationship requirement in this location?

A: None that I’m aware of. Since surgery departments may or may not be suites, the ASHRAE 170 ventilation Table 7-1 in the FGI Guidelines does not address that. You are correct that the actual operating room has to have a positive air pressure relationship to its surrounding areas. But I am not aware of any ventilation air-pressure requirement for the Surgery suite as measured at the suite entrance door.