The air in hospital operating rooms is sterilized by passing it through fine filters or through membranes with tiny pores.
Air leaving vessels in which pathogenic organisms are grown is sterilized by heating.
Commonly a single light switch turns on white light before a person enters, and the ultraviolet when the person leaves. There are also ultraviolet lights mounted in flow devices for water sterilization, but quartz bulbs or enclosures are needed to circumvent the attenuation of ultraviolet wavelengths. Such devices are also plagued by turbidity in the water and by dirt forming on the transparent surfaces.