Characterization of diesel-related pollutant migration in fire stations using low-cost direct-reading monitors

Fire engines and other vehicles housed within fire stations may generate diesel-related emissions that affect indoor air quality in both engine bays and adjacent occupied areas. This study characterized spatial and daily patterns of selected diesel-related indicator pollutants across three fire stations and evaluated associations between daily engine activity, relative distance from engine exhaust sources, and station characteristics. Multiple direct-reading air quality monitors were deployed at each station for seven consecutive days at fixed monitoring locations representing engine-bay and adjacent occupied spaces. Minute-level measurements of PM₁₀, PM_2.5, PM₁, NO₂, VOCs, and CO₂ were aggregated to daily means for statistical analyses. Associations were evaluated using Pearson correlations and hierarchical linear mixed-effects models with restricted maximum likelihood estimation. PM₁₀, NO₂, VOCs, and CO₂ demonstrated significant associations with selected predictors, including engine activity, source distance, and station (p < 0.05), although the direction and significance of these associations varied by pollutant. PM2.5 and PM1 were not significantly associated with these factors. Measurable pollutant concentrations were detected beyond engine bays, suggesting that pollutants or shared indoor sources may influence adjacent occupied spaces. These findings indicate that diesel-related pollutant levels in fire stations are influenced by operational and structural factors and support evaluating engineering and ventilation controls to reduce in-station exposure.