Characteristic of real-time airborne bacteria measurement and the response of low-cost particulate matter sensor: a pilot study

Low-cost particulate matter (PM) sensors (LCS) have increasingly gained attention for monitoring airborne particles in buildings. Although basic information about the accuracy of LCS is available, there is limited data on their response to bioaerosols. This pilot study aims to investigate the characteristics of real-time airborne bacteria measurements and the response of LCS. Four common bacterial strains (Staphylococcus epidermidis, Escherichia coli, Serratia marcescens, and Salmonella enterica) with equivalent optical diameters ranging from 0.8 to 1.5 μm were experimentally aerosolized and tested. The real-time mass and number concentrations of bioaerosols were monitored using the LCS and two reference devices: DustTrak and the Wideband Integrated Bioaerosol Sensor (WIBS-5). The results demonstrated strong linear correlations between the LCS measurements and reference data for PM_2.5 mass concentration, with high coefficients of determination (R²) ranging from 0.94 to 0.99. The regression slopes (representing the LCS-to-reference relationship) fell within a narrow range of 0.259–0.321 for PM_2.5 concentrations. Moreover, the aerosol decay rate is a common parameter used in indoor air quality studies to evaluate the effectiveness of ventilation and air-cleaning systems. The results indicated that the bioaerosol decay rates estimated from LCS data were comparable to those obtained from the WIBS-5. This study presents the first application using LCS for airborne bacteria measurement. The results establish an important reference database for LCS performance in bioaerosol monitoring, with potential applications in decay rate studies and the evaluation of air purification systems in indoor environments. © 2025 Elsevier Ltd.