When used properly, air cleaners and HVAC filters can help reduce airborne contaminants including viruses in a building or small space. By itself, air cleaning or filtration is not enough to protect people from COVID-19. When used along with other best practices recommended by CDC and other public health agencies, including social distancing and mask wearing, filtration can be part of a plan to reduce the potential for airborne transmission of COVID-19 indoors.
Air cleaners and HVAC filters are designed to filter pollutants or contaminants out of the air that passes thru them. Air cleaning and filtration can help reduce airborne contaminants, including particles containing viruses. Portable air cleaners (also known as air purifiers) may be particularly helpful when additional ventilation with outdoor air is not possible without compromising indoor comfort (temperature or humidity), or when outdoor air pollution is high.
In order for an air cleaner to be effective in removing viruses from the air, it must be able to remove small airborne particles (in the size range of 0.1-1 um). Manufacturers report this capability in several ways. In some cases, they may indicate particle removal efficiency for specific particle sizes (e.g. “removes 99.9% of particles as small as 0.3 um”). Many manufacturers use the Clean Air Delivery Rate (CADR) rating system to rate air cleaner performance. Others indicate they use High Efficiency Particulate Air (HEPA) filters. In order to select an air cleaner that effectively filters viruses from the air, choose: 1) a unit that is the right size for the space you will be using it in (this is typically indicated by the manufacturer in square feet), 2) a unit that has a high CADR for smoke (vs. pollen or dust), is designated a HEPA unit, or specifically indicates that it filters particles in the 0.1-1 um size range.