Upper

CDC recommends a layered strategy to reduce exposures to SARS-CoV-2, the virus that causes COVID-19. A layered strategy combines multiple prevention strategies such as consistent and correct use of masks, ventilation, physical distancing, cleaning and disinfection, and hand hygiene.

Ventilation interventions can help reduce the number of infectious viral particles (e.g., SARS-CoV-2) in the air. Ventilation interventions include opening windows, using fans, adding high-efficiency particulate air (HEPA) fan/filter systems, and adding upper-room ultraviolet germicidal irradiation (UVGI). This factsheet presents information on upper-room UVGI, which can be effective at reducing exposures to SARS-CoV-2 in some group settings.

Ultraviolet germicidal irradiation, or UVGI, is the use of ultraviolet (UV) energy to kill viral, bacterial, and fungal organisms. UVGI fixtures produce UV-C energy, which has shorter wavelengths than more penetrating UV-A and UV-B rays and pose less risk to human health. Upper-room UVGI refers to a disinfection zone of UV energy that is located above people in the rooms they occupy. This kills airborne pathogens in the room where they are released. Fixtures are installed to prevent direct UV exposures to people in the room.

Note: For airborne viral particles, upper-room UVGI systems provide air changes per hour that are similar to the introduction of clean air into the space.

Upper-room UVGI has been used for over 70 years to eliminate airborne pathogens. Since 1950, the bulk of the research on upper-room UVGI systems focused on controlling the spread of tuberculosis (TB). Current guidance [6 MB, 87 pages] from CDC and National Institute for Occupational Safety and Health (NIOSH) on the design, installation, testing, and safe operation of upper-room UVGI systems is based on science and practice-based evidence to control tuberculosis (TB).