Survey on indoor airborne particle and PM _2.5 in office buildings

Characterization and emission of indoor sub-micron aerosols have been of great interest. This study aimed at investigating for characteristics of particle concentrations for size distribution in office buildings. The number of size distributions, PM _2.5 and SPM (less than 10 μm) mass concentrations were measured in 15 large office buildings that were over 3,000m ² of total floor areas and had central HVAC systems. As a result, the mass concentration shows a bimodal distribution at around 0.2-0.3 μm and 4 μm, while the number concentration has a smaller peak at 0.02 to 0.05 μm. The results of other buildings have the same trend of particle size-distributions. Every mass concentration was relatively low, except for the building, which had smoking area inside. PM _2.5 ratios (PM _2.5/SPM conc.) were around 0.8, and therefore SPM forms the greater part of PM _2.5. The peak of mass concentration distribution around 0.2 μm has a great effect on PM _2.5 concentrations. The sub-micron particles might penetrate through filter media in HVAC systems from outdoor air.