Air sterilization
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. In rooms where microorganisms are cultured
the air may be exposed to ultraviolet light to reduce the number of
potential contaminants; ultraviolet light penetrates glass poorly,
so organisms in vessels such as shake flasks will not be killed.
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.