5.1 Reported particle size measurement is a function of both the actual particle dimension and shape factor, as well as the particular physical or chemical properties of the particle being measured. Caution is required when comparing data from instruments operating on different physical or chemical parameters or with different particle size measurement ranges. Sample acquisition, handling, and preparation can also affect the reported particle size results.

1.1 These test 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 test methods are described for sizing particles as follows:

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

1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.4 These test methods do not provide for sizing particles smaller than 5 μm.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.