Filtration in buildings can be a part of an overall risk mitigation approach but is not generally regarded as a solution by itself. There is no direct scientific evidence of benefit, but some reduced exposure can reasonably be inferred based on the ability of some filters to remove particles that contain a SARS-CoV-2 virus. More importantly, in most buildings and in most situations, filters may be considerably less effective than other infection control measures including social distancing, isolation of known cases, and hand-washing.