37.1 Introduction
The ability of air to contain and transport liquids, solids and living substances is
frequently overlooked or forgotten. After becoming airborne, organisms are able
to contaminate products through air as long as they stay viable, which depends
on a number of different parameters.
The conditions of sampling and analysis should be considered prior to the
choice of the sampler (Ambroiseet al., 1999). Microbes are notoriously difficult
to assess accurately under variable conditions and no single sampling or assay
method is suitable for all applications; rather the method needs to be tailored to
the application of interest (Griffiths & Stewart, 1999). Understanding the
airborne behaviour of microbes over a range of environmental conditions is vital
for recommendation of the handling, sampling and assessment of bioaerosols
(Griffiths & Stewart, 1999).
In order to effectively monitor air quality, the nature of bioaerosols as well as
the parameters affecting air sampling and assaying techniques have to be
understood. Aerosols exhibit complex aerodynamic behaviour resulting from a
combination of physical influences that affect success of the air sampling. The
bioaerosol sampling parameters and the choice of the sampler must be con-
sidered according to the process and aim of sampling. Generally, air samplers
must collect a representative sample of the required air fraction with a minimum
of stress caused to the microbes to maintain viability. Bioaerosol sampling
techniques consist of passive and active methods. The traditional passive air
sampling method is the use of sedimentation plates. Active sampling methods
are based on different mechanisms such as impaction, centrifugation, filtering
and electrostatic precipitation. In addition to bioaerosol sampling there are
37 Improvingair sampling
H. Miettinen, VTT Biotechnology, Finland