Numerical assessment of particle dispersion and exposure risk in an underground parking lot

The transient air flow, particle dispersion, and particle exposure risk during and after transient vehicle exhaust in an underground parking lot was investigated in the present study. The Realizable k-ε model together with particle transport theory was employed and a parking space with two cars idling and emitting exhaust and four cars at rest was established. A three-dimensional model was validated by comparing the simulated results with measured data in a residential underground parking lot of Harbin, China. Particle exposure risk during and after transient vehicle exhaust was also evaluated using the index of intake fraction. The simulation results showed that the stream of vehicle exhaust and particles dispersed from the space between two opposite cars in the upward direction during the first 30 s after vehicle exhaust was emitted. A remarkable downward dispersion of particles from the roof to the ground was observed after the vehicle stopped emitting exhaust. Intake fraction of particles increased linearly with time since exhaust and grew to approximately 1.4 × 10−3 for adult and 1.2 × 10−3 for child at 300 s after the vehicle exhaust stopped, respectively.