Relationship Between the Concentrations Of PM_2.5 Indoors Obtained by Using the Optical and Gravimetric Methods: Preliminary Analysis

The paper presents preliminary analysis of measurements of the mass concentrations of PM_2.5 in the indoor environment, obtained with the use of two optical instruments: (Grimm device and low-cost sensor) and a sampler based on the gravimetric method (SKC). It was found that the measurement of PM_2.5 using an optical device with active sampling underestimates the actual mass concentration of this mode (PM_2.5), while measurement using an optical device with passive sampling of air overestimates the concentration of PM_2.5. It has been shown that the physical relationship between the mass concentrations of airborne particles obtained with an optical sensor (C_sensor ) and concentrations obtained with the gravimetric method (C_grav ) is not linear. However, for practical reasons, the correct (“true”) concentration levels of PM_2.5 in an indoor environment can be estimated by converting sensor data according to a simple linear equation, i.e., C_grav = a C_sensor . The coefficient a for the sensor used was estimated at 0.45.