A method for the sampling and analysis of soluble and insoluble inorganic tungsten (7440337) in the air of the workplace environment was tested for NIOSH validation. Samples were collected on a 37 millimeter 0.8 micron Type AA Millipore cellulose ester filter. The filter was extracted with deionized water for soluble tungsten; for insoluble tungsten, the filter was acid digested, dried, extracted with dilute hydrochloric acid to remove impurities, and redigested. Both tungsten fractions were analyzed by flame atomic absorption spectrophotometry. The protocol for establishing NIOSH validation of the method was to analyze spiked and dynamically generated samples for soluble and insoluble tungsten, test the breakthrough capacity of the cellulose ester filter, test the storage stability of 12 spiked filters and 18 generated filters for soluble and insoluble tungsten, and assess the precision and accuracy of the method. The aerosol generation and sampling system was presented. The total error for sampling and analysis was less than 25 percent at the NIOSH recommended standard 95 percent of the time. The authors conclude that this method satisfies NIOSH criteria for validation.