Fine and ultrafine particles in 20 French dwellings related to time-activity diaries

International audienceFine particles (FP ; > 0,3 μm diameter) were measured continuously over a week in the living room of 20 French occupied dwellings with an optical particle counter (OPC) in the frame of the French national survey 2003-2005 conducted by the Observatory of Indoor Air Quality (OQAI). In a subset of 10 dwellings, ultrafine particles (UFP ; > 0,01 μm) were also measured with a condensation particle counter (CPC) during one evening. Particles 1-hour median levels vary between 4.3×103 and 6×104 part/cm3 for UFP and from 23 to 323 part/cm3 for FP > 3 μm. Max/min ratios vary between dwellings from 10 to 257 for FP and up to 15 for UFP. The maximum concentration for either FP or UFP occurred between 7 and 9 pm corresponding systematically with the maximum occupation rate of the living room. Reported activities and carbon monoxide (CO) monitoring allow to determine the specific sources of particles indoors, i.e. specific activity (tobacco smoke, air freshener, cooking, etc.), occupation without activity (particle resuspension), combustion (high CO), and outdoors (windows opening). RELEVANCE: Particles are a major pollutant in the indoor environment with contributions from both outdoor and indoor sources. Crossing measurements with time-activity diaries allowed to determine the major occurrence of particle pollution in dwellings within a typical week and to identify the major sources of particles. Occupation appears clearly to be a key factor as it implies the activation of direct or indirect sources (resuspension) of particles (both UFP and FP). It is thus important to adapt any strategy to reduce indoor particle exposure to the active occupation profile. UNCERTAINTY: Outdoor concentration of particles was not assessed during the experiment. It contributes to the background particle concentration especially when the windows are opened. Two OPCs and two CPCs were used in the study. Inter-instrument variations were below the measurement uncertainty (20% for CPC and 10% for OPC). The mean completion rate of time-activity diaries was 67% (23% standard deviation)