Air Pressure Requirements

Q: This question concerns isolation room negative pressure parameters. Our ICU isolation rooms have two sensors for air pressure; one located inside the room and the other located outside the room, of course. Could you tell me what the maximum and minimum negative pressure standard is supposed to be? Is there even such a standard? The CDC website says that if a room is negative then it’s fine. That seems too ambiguous for me. I’d like to see something more specific if possible. I want to be sure that our negative pressure monitors are configured correctly.

A: The ASHRAE standard 170-2013, which is incorporated into the 2014 FGI Guidelines, calls for 0.01 inches of water column (wc) of air pressure, when the air pressure relationship to surrounding areas is required to be positive or negative. This number is referenced in many sections inside ASHRAE 170-2013, such as: 7.2.1(e), 7.2.1(f), 7.2.2(a), 7.4.1, 7.5.1(c), 7.5.2(a). This seems to be the standard value for positive/negative air pressure. But I suggest you check with your state and local authorities to determine if they have additional requirements.