Mass Calibration and Relative Humidity Compensation Requirements for Optical Portable Particulate Matter Monitors: The IMPASHS (Impact of Smoke-free Policies in Eu Member States) Wp2 Preliminary Results

PP-30-010 Background/Aims: Better knowledge of particulate matter concentrations needs portable, reliable, user friendly, low cost, real time mass analyzers of particulate matter (PM2.5) and PM10. Optical particle counters (OPC) measuring mass have manufacturer calibration specific gravity “K” factor referred to polystyrene latex particles, which are completely different than those of the real world; therefore, they require specific calibrations. Measurements are also subject to relative humidity (RH) heavy interference. The aim of this study is to evaluate, within the Impact of Smoke-free Policies in Eu Member States WP2 Project, the performance of 4 different OPC's in environmental tobacco smoke and background urban pollution and to find the new “K” factors using 1 Model BAM-1020 with certificate number EPQM-0798-122 for comparison. Methods: All instruments have been operating in parallel measuring PM2.5 generated by cigarettes (ETS) indoor and by urban pollution outdoor, and the data were replicated 3 times. Results: “K” factors were widely different between manufacturer's model, instrument serial numbers, ETS, and urban pollution, ranging from 0.5 to 2.27. Correlation with BAM-1020 was ranging from 0.7500 to 0.9800 and Student t test from 0.3000 to 0.9500. RH interference resulted mathematically compensable up to 75% RH, but above becomes uncontrollable and sample drying becomes compulsory. Conclusion: OPCs are very reliable and accurate, but need specific calibration and special care in handling and elaboration of the measurements.