Determining the infiltration of outdoor particles in the indoor environment using a dynamic model

摘要

As people spend a significant portion of their time indoors,it is desirable to determine the fraction of outdoor particles that reach the indoor environment and the associated inter-and intra-home variability.This fraction depends on particle penetration efficiency and deposition rate.An alternative method for calculating the dynamic infiltration factor using time-dependent concentrations and air-exchange measurements is presented.We discuss the limitations of calculating the penetration rate and deposition velocity independently and find that the indoor/outdoor ratio often overestimates penetration efficiency.The dynamic infiltration factors are calculated for seven houses,for generally seven nights per house,for 17 particle size fractions.For the smallest particle size fraction (0.02-0.03 mu m),the mean infiltration factor across homes was 0.49,increasing up to 0.76 for the 0.2-0.3 mu m size fraction,and then decreasing steadily to.0.32 for the largest size fraction (4-6 mu m).The coefficients of variation between nights and homes were determined and are comparable,ranging between 0.07 and 0.18 for all the size fractions up to 1 mu m,with values up to 0.48 for larger size fractions.