The Effect of Portable Indoor Aerosol Filters on Indoor Air Quality (IAQ), Evidence from Different Sites in China

Abstract:

People spend most of their time indoors, and therefore exposure to aerosols and precursor-gasses both in the indoor environment, as well as those which may intrude into their indoor environment are of extreme concern for people’s health, well-being, working efficiency, and overall life quality. We employ portable indoor aerosol filters in combination with multiple air quality monitors, with the goal of measuring and understanding any improvement in Indoor Air Quality (IAQ), and/or mass transfer to/from the indoor environment. Since the effect of filters in real indoor environments have been inconsistent, a critical component of this study is to investigate this more robustly as a function of environmental, climatological, and dynamical phenomena.

The effect on portable indoor aerosol filters on IAQ is based on evidence from different sites including large cities, intermediate cities, and rural areas across Guangdong (Southern), Jiangsu (Eastern) and Henan (Central) China. The locations were chosen to represent a highly variable set of climate conditions and pollution levels. Indoor and outdoor measurements of PM₁, PM_2.5 and PM₁₀, as well as aerosol number concentrations over 5 size ranges from 0.3 to 10 microns were collected at 2 minute intervals over a minimum of 20 days at every location. We compared the effect of the filters under equilibrium conditions, during extreme indoor and outdoor emissions events, and under rapid changes in the weather.

Results showed that portable indoor aerosol filters improve IAQ under both equilibrium and event conditions. Comparing measurements taken without filter and with filter, the ratio of indoor to outdoor pollution level decreased during equilibrium condition. When using filters, decay time, tau and drop in magnitude of events also decreased, although the effect ranged from obvious under certain conditions to subtle under other conditions. Our study further supports the efficacy of using portable indoor aerosol filters to improve IAQ, but also introduces conditions and disclaimers under which the benefits may be enhanced or reduced. One such conclusion is that ventilation may frequently lead to an overall worsening of IAQ.