ASTM D8358-21

5.1The following is a non-exclusive list of standards to which this guide applies: Guide D6062; Test Methods D4185, D4532, D6785, D7035, D7439, D7948; and Practices D6061 and D6552.

5.2The applicability of this guide to other standards under the jurisdiction of ASTM Committee D22, but not the direct responsibility of Subcommittee D22.04, should be considered where analyte entry into the sampler is considered the sample and where analyte adherence to internal sampler surfaces (walls) is likely to scavenge analyte from the collection substrate.

5.3Aerosol samplers typically consist of a filter or other collection substrate, for example an impaction plate or foam, supported in a container or holder. The entire device typically is considered an aerosol sampler. The sampling efficiency of the aerosol sampler, that is, the ratio of the concentration collected by the collection substrate to the undisturbed concentration in the air, has three components: (5.4Part of the aerosol entering a sampler will deposit on the internal surfaces of the sampler prior to reaching the collection substrate. There are number of mechanisms by which this can occur, including bounce from the filter, inertial impaction, gravitational settling and electrostatic attraction after entry. In addition, after sample collection, if the collection substrate is transported while mounted in the sampler, it is possible that particles originally deposited on the collection substrate may dislodge during transportation. Such particles can thereby contribute to deposits on the walls, as well as on the base of any cover plate or plug. All particles found elsewhere than on or in the collection substrate are often loosely termed wall deposits. If the sample of interest entails the entire aspirated air particulate into the container or holder (sampler), it is necessary to account for these wall deposits, especially if it cannot be shown that they should be disregarded.

5.5The research underpinning the information in this guide has arisen partly from studies of inert particles (3, 4), but mostly from investigations of methods for the determination of airborne metalliferous particulates 5.6The findings of studies that have been carried out to assess wall deposits in two commonly used samplers are summarized in Table 1 and Table 2. A commonly used sampler, the 37-mm closed-face polystyrene cassette (CFC), is specified as the sampler of choice in many U.S. National Institute for Occupational Safety and Health (NIOSH) and U.S. Occupational Safety and Health Administration (OSHA) methods 5.7The Gesamtsstaubprobenhame (GSP) inhalable sampler, and similar metal or plastic versions referred to as a conical inhalable sampler (CIS), has not been the subject of similar extensive investigations of wall deposits. While the GSP met the inhalable convention in a European study without considering wall deposits for particles up to 25 m AED 5.8No pattern has been discerned that might allow for correction factors to be used in any single sampler without introducing too great an uncertainty into the result 5.9Samplers for the ISO 7708 respirable fraction of dust have filters contained in holders downstream of (after) the size-separation device, typically a cyclone. These sample holders, where not electrically conductive, have also been shown to exhibit significant proportions of wall deposits. In a study of field samples 1.1Many methods for sampling airborne particulate matter entail aerosol collection on a substrate (typically a filter) housed within a container (or holder), the whole apparatus being referred to as an aerosol sampler. In operation, the sampler allows a vacuum (pressure below ambient or room air pressure) to be applied to the rear of the substrate so that sampled air will pass through the substrate, leaving collected particles on the substrate for subsequent analysis. The sampler may also protect the substrate, while the opening (orifice) of the container may further play some role in determining what size range(s) of particles approach the collection substrate (size-selective sampling).

1.2All particles entering the container orifice are considered part of the sample, unless stated otherwise in the method, but not all particles are necessarily found on the substrate after sampling 1.3Wall deposits may also occur in multi-stage samplers (for example, cascade impactors), but this guide does not cover such samplers.

1.4The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5This 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.

1.6This 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.