Operating Instructions MD8 Airport
9
Device Description
3.1.3 Air Inlet
The air inlet opening holds the adapter for the filter holder or culture media plate .
Fig . 2: Air inlet (with adapter and filter holder, and with adapter and culture media plate)
Pos. Designation
Description
1
Adapter and filter holder
Required for air sampling using the
filtration method .
2
Adapter and culture media plate
Required for air sampling using the
impaction method .
3.2 Air Sampling
3.2.1 Filtration Method
In the filtration method, a defined volume of air is sucked in through gelatin
membrane filters . Microorganisms and viruses are trapped on the filters . Since
the filters contain
no
substances on which cultures can grow, they need to be
transferred to a suitable culture medium and incubated once the air sampling is
complete . Following incubation, the number of culture-forming units per cubic
meter of air (cfu / m
3
) can be calculated from the number of colonies growing on
the culture medium in relation to the volume of air sampled .
3.2.2 Impaction Method
In the Andersen Principle impaction method, a defined volume of air is sucked
through a strainer, accelerated and passed across a culture media plate . Due to
inertia, the microorganisms present in the air
cannot
follow the diverted air flow
and are thrown onto the culture media plate . Following incubation of the culture
media plate, the colonies that have grown on the culture medium are counted in
terms of culture-forming units (cfu / m
3
) .
3.3 Controlling the Air Flow Rate
The air flow rate is constantly measured by means of a fan wheel anemometer with
opto-electronic scanning, and is digitally controlled .
1
2
