Assessment of PM1 number concentration with respect to traffic flow and thermal environment in a residential underground garage

Particles with aerodynamic diameters < 1 μm (PM1) damage human health more severely than do coarse particles. In this study, PM1 number concentration, traffic flow, temperature and relative humidity in both a residential underground garage and at the entrance/exit, wind velocity at the entrance/exit were measured between May and June 2012 in Harbin, China. Pearson and partial correlations were employed to quantify the relationship between PM1 number concentration, traffic flow, and the thermal environment. The results show that mean PM1 number concentration in the garage during the measurement was 21,905 particles cm−3, which was approximately 1.54 times higher than the outdoor environment. Mean traffic flow, with a value of 0.2 vehicles min−1, may be the most important factor impacting PM1 pollution levels in the garage. The effects of air temperature inside the garage and wind velocity at the entrance/exit on PM1 pollution may be stronger compared with other environmental parameters. An inverse relationship between air temperature and PM1 number concentration was observed and decrease in wind velocity at the entrance/exit resulted in increased PM1 number concentration. This study provides fundamental reference data for PM1 number concentration levels in a residential underground garage.