What is the minimum air change rate per hour (ACH) generally required for a protective environment (PE) room designed for immunocompromised patients?

According to guidelines such as those outlined in ASHRAE Standard 170, Ventilation of Health Care Facilities, a Protective Environment (PE) room designed for immunocompromised patients generally requires a minimum air change rate per hour (ACH) of 12. An air change rate refers to the number of times the air in a room is completely replaced with filtered air in one hour. A PE room is a specialized hospital room designed to protect patients with weakened immune systems from airborne pathogens. In addition to the 12 ACH minimum, the air must be HEPA-filtered to remove 99.97% of particles 0.3 micrometers in size or larger, and the room must maintain a positive pressure relationship relative to surrounding areas. This positive pressure ensures that air flows out of the room when the door is opened, preventing unfiltered air from entering. The high ACH and HEPA filtration help to maintain a clean and safe environment for these vulnerable patients.