Field-based evaluation of the filtration performance of indigenous face coverings in stone carving work: Evidence from Dausa district, Rajasthan

Stone carving activity generates a high concentration of airborne particulate matter (PM), posing serious respiratory risks to workers operating in close proximity to emission source(s). This field study has been conducted at an active stone-carving site in the Dausa district of Rajasthan, India and evaluates real-world filtration performance of commonly used face coverings: surgical mask and dry/wet gamcha (traditional cotton cloth widely used in this occupational setting). A mannequin-based dual optical particle counter (OPC) setup has been used, enabling the simultaneous monitoring of PM concentrations inside and outside masks. Performance has been assessed as the difference in these PM concentrations and the corresponding filtration efficiency (FE). Calibrated instruments have been inter-compared prior to deployment, and correction factors have been applied to the observed concentrations. High difference in outside and inside PM concentration ranging from 6–83, 7–131.8 and 31–171 µg/m³ (PM1), 11–505, 10–365, and 45–386 µg/m³ (PM2.5), 114–7317, 623–5105, and 108–7411 µg/m³ (PM10), has been observed for surgical mask, dry gamcha, and wet gamcha, respectively. Overall, FE varies from 37.1–73.2%, 62.2–84% and 67.6–76.8% for surgical mask, dry gamcha, and wet gamcha, respectively. Gamcha filtration efficiency varies with particle size: wet gamcha performs better for PM1, with similar performance for PM2.5, and dry gamcha performs better for PM10, whereas surgical masks exhibit lower overall efficiency. Fluctuating emission intensity and leakage effect may govern the real-time performance of masks. While face coverings may offer limited protection against dust inhalation in stone carving industries, sustainable dust reduction requires engineering controls such as improved tools, vacuum shrouds, and regular housekeeping practices. Copyright © 2026 American Association for Aerosol Research