Characterization of indoor diesel exhaust emissions from the parking garage of a school

Abstract

Diesel exhaust (DE) emissions from a parking garage located in the basement of a school were characterized during spring and winter using direct reading devices and integrated sampling methods. Concentrations of CO and NO₂ were evaluated using electrochemical sensors and passive colorimetric tubes, respectively. Elemental and total carbon concentrations were measured using the NIOSH 5040 method. Particle number concentrations (PNCs), respirable particulate matter (PM_resp) mass concentrations, and size distributions were evaluated using direct reading devices. Indoor concentrations of elemental carbon, PNC, CO, and NO₂ showed significant seasonal variation; concentrations were much higher during winter (p < 0.01). Concentrations of the PM_resp and total carbon did not show significant seasonal variation. Pearson correlation coefficients were 0.9 (p < 0.01) and 0.94 (p < 0.01) between the parking garage and ground floor average daily PNCs, and between the parking garage and first floor average daily PNCs, respectively. Since DE is the main identified source of fine and ultrafine particles in the school, these results suggest that DE emissions migrate from the parking garage into the school. Our results highlight the relevance of direct reading instruments in identifying migration of contaminants and suggest that monitoring PNC is a more specific way of assessing exposure to DE than monitoring the common PM_resp fraction.

Keywords: Diesel; Elemental carbon; Exposure; Number concentration; School bus; Ultrafine particles.