ASTM F312-97

1.1 These methods cover the determination of the size distribution and quantity of particulate matter contamination from aerospace fluids isolated on a membrane filter. The microscopical techniques described may also be applied to other properly prepared samples of small particles. Two methods are described for sizing particles as follows:

1.1.1 Method A -Particle sizes are measured as the diameter of a circle whose area is equal to the projected area of the particle.

1.1.2 Method B -Particle sizes are measured by their longest dimension.

1.2 The test methods are intended for application to particle contamination determination of aerospace fluids, gases, surfaces, and environments.

1.3 These methods do not provide for sizing particles smaller than 5 [mu]m.

Note 1-Results of these methods are subject to variables inherent in any statistical method. The use of these methods as a standard for initially establishing limits should be avoided unless ample tolerances are permissible.