Size Distribution of Indoor Airborne Particulates Collected by a Low-Flow Rate Cascade Impactor

A simple, low-flow rate cascade impactor operated by a battery-driven minipump was developed to collect fine airborne particulates in various environmental situa tions. Its performance in collecting size-fractionated par ticulate matter was demonstrated to be satisfactory by comparing it with a conventional TEOM particulate mon itor. The sampler was used to survey size distributions of indoor and outdoor airborne particulates in 20 homes in several Japanese cities, 10 nonsmoking and 10 in which there was at least 1 smoker. The arithmetic mean con centrations and concentration ranges of particulate mat ter of less than 2.5 μm aerodynamic diameter (PM2.5) out doors, in living rooms, kitchens and bedrooms were of similar magnitude. The minimum PM2.5/PM 10 ratio was higher in bedrooms than outdoors or in other rooms, indicating that the coarse particles precipitated possibly as a result of lower turbulence due to a shorter period of occupancy and lower activity during it. The correlations between PM10 and PM2.5 concentrations, both indoors and outdoors, were significant. The correlations be tween total suspended particulates and PM10 levels were also significant. Overall no significant correlations were found between total suspended particulates, PM10 and PM2.5 concentrations outdoors and those in living rooms or bedrooms. This supports the fact that there were indoor particulate sources including tobacco smoke.