“…In Germany, the mean PM 4 concentrations in smoker households amounted in winter and summer, for instance, to 109 µg/m³ and 59 µg/m³ respectively, and in non smoker households they amounted during the two seasons only to 28 µg/m³ (Fromme et al, 2005). Other important influencing factors for the indoor air contents are the season, the outdoor air, the ventilation behaviour, the age and the location of the buildings and indoor activities such as cooking, the use of ovens and the burning of incense sticks (Mönkkönen et al, 2005;Martuzevicius et al, 2008;Santen et al, 2009;Rodes et al, 2010;Héroux et al, 2010;Byun et al, 2010;Raaschou-Nielsen et al, 2011).…”