Characteristics of particle number and mass concentrations in residential houses in Brisbane, Australia

Diurnal variation of indoor submicrometer (0.007-0.808 mum) particle number and particle mass (approximation of PM2.5) concentrations was investigated in 15 houses in a residential suburb of Brisbane during winter in 1999. Continuous monitoring for more than 48 h was conducted using a condensation particle counter (CPC) and a photometer (DustTrak) in the kitchen of each house, and the residents kept diaries of the activities conducted. In addition, data from a central monitoring station was used to investigate indoor/outdoor relationships. The results show that there were clear diurnal variations in both particle number and approximation of PM2.5 concentrations, for all the investigated houses. The pattern of diurnal variations varied from house to house, however, there was always a close relationship between the concentration and human indoor activities. The average number and mass concentrations during indoor activities were (18.2 +/-3.9) x 10(3) particles cm(-3) and (15.5+/-7.9) mug m(-3), respectively, and under non-activity conditions, (12.4+/-2.7) x 10(3) particles cm(-3) (11.1+/-2.6) +/- mug m(-3), respectively. In general, there was a poor correlation between mass and number concentrations and the correlation coefficients were highly variable from day to day and from house to house. This implies that conclusions cannot be drawn about either one of the number or mass concentration characteristics of indoor particles, based on measurement of the other. The study also showed that it is unlikely that particle concentrations indoors could be represented by measurements conducted at a fixed monitoring station due to the large impact of indoor and local sources. (C) 2003 Elsevier Ltd. All rights reserved.