Figure 2. Concentrations of fine particles (PM2.5), and particulate matter (PM10) and indoor (I) and outdoor (O) levels in different study locations during the summer period

From

Variation of Indoor/Outdoor Particulates in Tallinn, Estonia – the Role of Ventilation, Heating Systems and Lifestyle

Hans Orru, Alo Mikola, Madis Upan, Teet-Andrus Koiv

Journal of Environment Pollution and Human Health. 2014, 2(2), 52-57 doi:10.12691/jephh-2-2-3