||This report presents a region-wide summary of air monitoring sites which are part of the National Air Sampling Network (NASN). The network in Region VIII consists of fifteen sites, all of which contain one high volume sampler to measure total suspended particulate, and seven of which have, in addition, gas bubblers to measure ambient concentrations of SO2 and NO2. Since January 1974, the EPA Regional Office in Denver has been responsible for network operation, maintenance, and calibration of equipment. The operators of the sites are volunteers from the Forest Service, National Park Service, or State or local air pollution agencies. All necessary supplies, including filters and bubblers, are sent to the operators by the EPA Regional Laboratory and samples are returned to the Laboratory after sampling has occurred. Samples are run from midnight to midnight (24-hours) on the days indicated by the 6-day sampling schedule (see Appendix B). The Laboratory analyzes the samples according to standard methods and reports concentrations in micrograms per cubic meter of air (microgram/cu m). Twice each year, EPA personnel inspect the sites, replace worn equipment and calibrate the instruments. Further analyses are done on every other filter from each site by EPA. Filters are analyzed for nitrates, sulfates, ammonia, and organics. Data obtained is contained in this report.