Characterization of indoor sources of fine and ultrafine particles: a study conducted in a full-scale chamber Introduction In recent years, exposure to fine and ultrafine airborne particles has been identified as an important factor affecting human health (Alvin et al., 2000; Oberdo¨ rster et al., 1994; Schwartz et al., 1996; Seaton et al., 1995). Several researchers hypothesize that an increased mortality rate is associated with the particle levels prevailing in urban air (Dockery et al., 1993; Jamriska et al., 1999). People suffering from allergies and respiratory diseases such as asthma have been identi- fied as being especially sensitive to air pollution. The awareness of the impact of airborne particles, particularly fine and ultrafine particles (UFPs), on health is growing. Ultrafine particles can penetrate deeper into the respiratory system and can deposit there with a higher probability than larger particles because of their larger diffusion coefficient. A recent study indicates that peak concentrations may be more important for health effects than long-term concentra- tion averages (Garrett et al., 1998). Industry, heating plants and traffic are examples of important outdoor particle sources. Particles generated by these sources may enter buildings through infiltra- tion and by air supplied to the building via the ventilation system. For example, in office buildings Abstract Humans and their activities are known to generate considerable amounts of particulate matter indoors. Some of the activities are cooking, smoking and cleaning. In this study 13 different particle sources were for the first time examined in a 32 m 3 full-scale chamber with an air change rate of 1.7 ± 0.1/h. Two different instruments, a condensation particle counter (CPC) and an optical particle counter (OPC) were used to quantitatively determine ultrafine and fine particle emissions, respectively. The CPC measures particles from 0.02 lm to larger than 1.0 lm. The OPC was adjusted to measure particle concentrations in eight fractions between 0.3 and 1.0 lm. The sources were cigarette side-stream smoke, pure wax candles, scented candles, a vacuum clea- ner, an air-freshener spray, a flat iron (with and without steam) on a cotton sheet, electric radiators, an electric stove, a gas stove, and frying meat. The cigarette burning, frying meat, air freshener spray and gas stove showed a par- ticle size distribution that changed over time towards larger particles. In most of the experiments the maximum concentration was reached within a few minutes. Typically, the increase of the particle concentration immediately after activation of the source was more rapid than the decay of the concentration observed after deactivation of the source. The highest observed concentration of ultrafine particles was approximately 241,000 particles/cm 3 and originated from the combustion of pure wax candles. The weakest generation of ultrafine particles (1.17 · 10 7 particles per second) was observed when ironing without steam on a cotton sheet, which resulted in a concentration of 550 particles/cm 3 in the chamber air. The highest generation rate (1.47 · 10 10 particles per second) was observed in the radiator test. A. Afshari 1 , U. Matson 2 , L. E. Ekberg 2,3 1 Danish Building and Urban Research, Energy and Indoor Climate Division, Hørsholm, Denmark, 2 Department of Building Technology, Building Services Engineering, Chalmers University of Technology, Gçteborg, Sweden, 3 CIT Energy Management AB, Chalmers Industriteknik, Gçteborg, Sweden Key words: Indoor air quality; particle generation rate; condensation particle counter; number concentration. Alireza Afshari Danish Building and Urban Research Energy and Indoor Climate Division Dr Neergaards Vej 15 DK-2970, Hørsholm Denmark Tel.: +45 4586 5533 Fax: +45 4586 7535 e-mail: ala@dbur.dk Received for review 1 July 2004. Accepted for publication 18 January 2005. Ó Indoor Air (2005) Practical Implications Humans and their activities are known to generate substantial amounts of particulate matter indoors and potentially they can have a strong influence on short-term exposure. In this study a quantitative determination of the emissions of fine and ultrafine particles from different indoor sources was performed. The aim is a better understanding of the origin and fate of indoor particles. The results may be useful for Indoor Air Quality models. Indoor Air 2005; 15: 141–150 www.blackwellpublishing.com/ina Printed in Denmark. All rights reserved Copyright Ó Blackwell Munksgaard 2005 INDOOR AIR doi:10.1111/j.1600-0668.2005.00332.x 141