Air Samplers (active air sampling) – Air samplers draw in predetermined volumes of air. The air is drawn over a sterile media plate, which is later incubated to reveal the number of viable organisms per cubic feet or liter. Currently agar impaction is the method of choice throughout the industries. Using a specially designed, and calibrated piece of equipment which holds the media plate under a perforated lid and draws in a known amount of air one can accurately measure the amount of viable bacteria within the air.
Settling plates (passive air sampling) - Petri dishes containing sterile growth media are exposed to the environment for a specific period of time, usually between 30-60 minutes but can be exposed up to four hours before compromising the integrity of the media itself. Viable microorganisms which settle onto the media surface will grow after the plates are incubated. However, passive air sampling is tending to be phased out because it does not reflect microbial contamination with an accurately measured volume of air.
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