Continuous monitors were employed for one year in an occupied townhouse to measure ultrafine, fine and coarse particles, air change rates, wind speed and direction, temperature and relative humidity. A main objective was to document long-term variation in indoor air concentrations due to (1) diurnal and seasonal variation of outdoor air concentrations and meteorological variables, (2) indoor sources such as cooking and using candles, and (3) activities affecting air change rates such as opening windows and using fans. A second objective was to test and compare available instruments for their suitability in providing real-time estimates of particle levels and ancillary variables. Despite different measuring principles, the four instruments employed in this study agreed reasonably well. The Aerodynamic Particle Size (APS), Climet, and MIE personal data RAM instruments agreed to within 10 % to 30 % in their overall estimates of fine and coarse particle volumes. The Scanning Mobility Particle Size (SMPS) also agreed well with the other three instruments in the overlap region (0.3 υm to 0.5 υm) when one inlet was employed, but appeared to overestimate the values in the larger overlap region (0.3 υm to 1 υm) when a larger inlet was employed. Indoor sources such as cooking with natural gas and simple physical activities such as walking accounted for a majority of the ultrafine and coarse particle concentrations, whereas outdoor sources were more important for particles between 0.1 υm and 1 υm in diameter. Indoor sources affected ultrafine particle concentrations 22 % of the time, and fine coarse particle concentrations between 12 % and 15 % of the time. Averaged for the entire year, the number distribution was bimodal, with peaks at about 10 nm (possibly smaller) and around 40 nm to 46 nm. The volume distribution was also bimodal, with apeak at about 209 nm to 217 nm, a minimum at about 1 υm to 1.2 υm, and then an upward slope again through the remaining size fractions (up to 20 υm). A database was created on a 5 min averaging time basis and contains more than 90,000 measurements by the APS and SMPS, and about 30,000 by the Climet and MIE. About 4500 hour long average air change rates were also recorded.
Citation: Air and Waste Management Association and the Environmental Protection Agency
Pub Type: Journals
indoor air quality, infiltration, occupant behavior, particle instruments, particulate matter