"This SAE Aerospace Recommended Practice (ARP) describes two procedures for sampling particles in dust controlled spaces. One procedure covers airborne dust above 5 ?m. The other (and newly added procedure) covers particles of 25 ?m 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 ?m 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 ?m 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 ?m 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."