Q: How frequently air should be changed in negative pressure rooms in ICU?
Answer: 6 to 12 air changes per hour
Infected particles from respiratory secretions less than 5 microns can stay suspended in the air for a considerable period of time and may get inhaled by people in the surroundings. Airborne precautions are advised for infections like tuberculosis, measles, varicella, smallpox, and SARS viruses (including COVID-19).
In ICUs airborne isolation is usually done in 'negative pressure rooms'. These rooms should have changed air for at least 6 to 12 times per hour. The door of the room needs to stay closed and caretakers should ideally be wearing N-95 masks. All healthcare workers should be tested for fitting their N-95 masks for a tight seal.
Said that, controversy does exist about negative pressure rooms' efficacy in protecting healthcare workers (see reference # 4).
Reference:1. Jensen PA, Lambert LA, Iademarco MF, et al. Guidelines for preventing the transmission of Mycobacterium tuberculosis in health-care settings, 2005. MMWR Recomm Rep 2005; 54:1.