Description / Abstract:
This SAE Aerospace Recommended Practice (ARP) describes two
procedures for sampling particles in dust controlled spaces. One
procedure covers airborne dust above 5 µm. The other (and newly
added procedure) covers particles of 25 µm and larger that "fall
out" of the environment onto surfaces. In each case the particles
are sized in the longest dimension and counted. Airborne particles
are reported as particles per cubic meter (cubic foot) whereas
particles collected in fall out samples are reported as particles
per 0.1 square meter (square foot). This document includes English
units in parentheses as referenced information to the SI units
where meaningful.
These procedures may also be used for environmental analysis
where the quality of the particles by visual or chemical analysis
is intended.
Field of Application:
Airborne particle sampling (volumetric samples) - This procedure
may be used in lieu of automatic particle counters for verifying
conformance with FED-STD-209 for cleanroom classes above 10,000
unless the user or contracting agency specifies the counting of 0.5
µm particles. It may also be used for environmental analysis where
the quality of the particles by visual identification is
desirable.
This procedure can be used as a rough correlation check of
particles greater than 5 µm when calibrating automatic particle
counters.
Limitations and Errors:
This procedure is a slower alternative to the method by
automatic particle counter, but necessary when the identification
of particles is a concern.
This procedure is not appropriate when particles below 5 µm are
of concern.
The procedures herein are not recommended to evaluate the
residues that may collect on residue sensitive instruments such as
optics and sensors. These residues, sometimes called non-volatile
residue (NVR) or volatile condensable material (VCM) are best
sampled by other means.
One source of error in these procedures is a poor distribution
of particles on the membrane filter surface (see.3.8.6) while
another is from errors occurring during the microscopic
analysis.