1. Scope:1.1 This test method covers determination of surface area of airborne metal and metal oxide nanoparticles in inhalation exposure chambers for inhalation toxicology studies. The test method permits the use of any modern commercial krypton adsorption instruments but strictly defines the sample collection, outgassing, and analysis procedures for metal and metal oxide nanoparticles. Instrument-reported values of surface area based on the multipoint Brunauer, Emmett, and Teller (BET) equation (Brunauer et al, 1938; Gregg and Sing, 1982; Anderson, 1975) are used to calculate surface area of airborne nanoparticles collected on a filter. 1.2 This test method uses SI units as the standard. State all numerical values in terms of SI units unless specific instrumentation software reports surface area using alternate units. 1.3 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 and health practices and determine the applicability of regulatory limitations prior to use.A tiered strategy for characterization of nanoparticle properties is necessary to draw meaningful conclusions concerning dose-response relationships observed during inhalation toxicology experiments. This tiered strategy includes characterization of nanoparticles as produced (that is, measured as the bulk material sold by the supplier) and administered (that is, measured at the point of delivery to a test subject). This test method may be used by government agencies, academic researchers, consultants, and others who perform inhalation toxicology experiments.