The Clean Air Act of 1970 created the National Ambient Air Quality Standards (NAAQS), which regulated Total Suspended Particulates. In 1987 the EPA revised the NAAQS to regulate PM 10 and again in 1997 to include PM 2.5. As a result of a court case the 1997 revision has been remanded back to the EPA because of constitutional questions about EPA's ability to arbitrarily set the NAAQS. The EPA has filed to have the case overturned and the issue is currently in the court system. The outcome is uncertain, but it is evident that a PM 2.5 standard will be implemented. Therefore, it is necessary to determine the PM 2.5 concentrations in the ambient air and from specific sources for both scientific and regulatory purposes. To do this an accurate measure of PM 2.5 is necessary. The existing Federal Reference Method (FRM) sampler has a number of problems that make its usefulness questionable. Most of these problems stem from its low flow rate of 1 m³/hr (0.6 ft³/min). This low flow rate brings up questions of how representative the sample is of the ambient air and problems with accurately measuring mass of particulate matter on the filter. There are a number of studies showing that small cyclones can be used to obtain a cutpoint of 2.5 microns at a significantly higher flow rate (68 m³/hr, 40 ft³/min) than the existing FRM sampler and other PM 2.5 samplers. Research is in progress to develop and test a cyclone-based sampler at this higher flow rate.