Comparative assessment of a real-time particle monitor against the reference gravimetric method for PM ₁₀ and PM _2.5 in indoor air

Accurate monitoring of indoor mass concentrations of particulate matter is very important for health risk assessment as people in developed countries spend approximately 90% of their time indoors. The direct reading, aerosol monitoring device, Turnkey, OSIRIS Particle Monitor (Model 2315) and the European reference low volume sampler, LVS3 (Sven/Leckel LVS3) with size-selective inlets for PM ₁₀ and PM _2.5 fractions were used to assess the comparability of available optical and gravimetric methods for particulate matter characterization in indoor air. Simultaneous 24-hour samples were collected in an indoor environment for 60 sampling periods in the town of Bor, Serbia. The 24-hour mean PM ₁₀ levels from the OSIRIS monitor were well correlated with the LVS3 levels (R ²=0.87) and did not show statistically significant bias. The 24-hour mean PM _2.5 levels from the OSIRIS monitor were moderately correlated with the LVS3 levels (R ²=0.71), but show statistically significant bias. The results suggest that the OSIRIS monitor provides sufficiently accurate measurements for PM ₁₀. The OSIRIS monitor underestimated the indoor PM ₁₀ concentrations by approximately 12%, relative to the reference LVS3 sampler. The accuracy of PM ₁₀ measurements could be further improved through empirical adjustment. For the fine fraction of particulate matter, PM _2.5, it was found that the OSIRIS monitor underestimated indoor concentrations by approximately 63%, relative to the reference LVS3 sampler. This could lead to exposure misclassification in health effects studies relying on PM _2.5 measurements collected with this instrument in indoor environments.