Oftion [23]. The worst day for particulate matter concentration was on 14 December 2020 when the maximum concentrations for PM2.five and PM10 have been 235 /m3 and 343 /m3 , respectively. These results confirm a really high particulate matter pollution issue in Poland [30]. The outdoor air quality evaluation results show that PM concentrations are characterized by seasonality in nations using a cold and temperate climate. Larger concentrations of PM were recorded in the winter and that characterization was confirmed when particulate matter decreases had been observed when the external air temperature increased. We concluded the dominant supply of pollution was low emission from heat sources made use of to heat buildings positioned close to the analyzed facilities. This confirmed results reported by other authors that indicated that particulate matter concentrations increased throughout the heating season [9,23,26,31], and the heating season will be the greatest predictor of (-)-Bicuculline methochloride Antagonist indoor particulate matter concentration [32]. In analysis from Portugal [25], the PM10 concentration was 75 /m3 inside the winter and 60 /m3 in the spring. The sources of particulate matter and its seasonality were not analyzed by the authors, but the concentrations in spring have been reduce than in winter, in contrast to investigation in Poland. This may well indicate other sources of particulate matter than heating buildings, as the climate in Portugal is warmer than in Poland. 4.3. Airing of Rooms and Its Impact on Indoor Air Quality The very good air quality within the room, which implies that there’s a superior air exchange, could be described together with the amount of carbon dioxide concentration within the area [33]. Based on the literature, CO2 concentrations that indicate excellent air exchange are 10001500 ppm [12,13]. The principle cause for the higher concentration of CO2 in rooms will be the lack of mechanical ventilation and the insufficient frequency of opening windows when the rooms are in use [12,34]. Airing the rooms various instances each day lowers the regularly rising concentration of CO2 in the area. Nursery B4, using the lowest CO2 concentration within the winter, was intensively aired (Figures 5d and 6b). Even 15 min of airing the space decreased the CO2 concentration by as much as 450 ppm. In nursery B1, with the worst levels of CO2 , airing took place sporadically (Figure 6a). Really high levels of CO2 at the end on the day in playrooms B1 and B2 had been 2400 ppm and 1800 ppm, respectively, and resulted in the lack of space ventilation. Even if the purpose for the lack of ventilation is the worry of lowering the temperature on the internal air throughout the winter, when the outdoors temperature is low (the typical outdoors temperature in winter (W) was three.two C), rooms nonetheless will need adequate ventilation. With an efficiently operating heating program, the internal air temperature will return to standard relatively promptly with a short-term supplier of cold outdoors air. In institutions where a distinct area is intended for the midday nap, the lack of airing the playroom in the course of this time is unjustified. Facility B3 will not possess a separate sleeping area, all activities take location in one area, plus the highest concentration of CO2 was recorded in the middle of your day, (nap time, 1700 ppm). Airing the room soon after a nap through lunch resulted within a CO2 concentration reduction by 500 ppm. However, airing the rooms, which lowers the CO2 concentration, involves the direct introduction of outdoors air in to the room. In nursery B4, the rooms were aired for the duration of naps, but that in.