As part of its Air Climate & Energy (ACE) research program on emerging technologies (ACE EM-3), the US EPA developed a research effort with the goals of: conducting a worldwide market survey of low cost PM sensors (<$2500), acquiring such sensors, and then conducting collocated field evaluations of these sensors in direct comparison with FEM instrumentation. A total of eight such devices were obtained and sited in the established PM sensor test platform on the US EPAs RTP, NC campus (AIRS). The collocated PM2.5 FEM instrumentation with 5-minute time resolution provided the means to investigate both short duration and daily (24-hr) comparisons between the test devices and the FEM response. Potential data confounders such as temperature and relative humidity were obtained to aid in the investigation. The relationship between FEM response and the various sensors was established in a regression. Ancillary findings related to ease of use, portability, data collection efficiency, among others, were established based upon our experiences over approximately one month of continuous operation.