There are a lot of microorganisms found the air

 Mostly microorganisms found in
air are bacteria. These are determined by
the air sampling methods . Growth of these
microbes on nutrient media helps to
identify them.
According to United States
Pharmacopoeia (USP) Chapter <1116> ,
identification of environmental isolates
must be included in environmental control
program and it is useful in investigation of
source of contamination in pharmaceutical
products. Method of identification should
be verified and automated methods
should also be qualified before their use.
Generally pharmaceutical laboratories
have reference culture s of only pathogens
and other organisms specified for
analysis. There is wide range of
microorganisms found in air and water.
Therefore, it is not possible to identify
these microorganisms using culture
media with reference cultures.