TVOCs and PM 2.5 in Naturally Ventilated Homes: Three Case Studies in a Mild Climate

Abstract

In southern Europe, the present stock of social housing is ventilated naturally, with practice varying in the different seasons of the year. In winter, windows are kept closed most of the day with the exception of short periods for ventilation, whereas the rest of the year the windows are almost permanently open. In cold weather, air changes depend primarily on the air infiltrating across the envelope and when the temperature is warm, on the air flowing in through open windows. CO2, PM2.5, and TVOC concentration patterns were gathered over a year’s time in three social housing developments in southern Europe with different airtightness conditions and analyzed to determine possible relationships between environmental parameters and occupants’ use profiles. Correlations were found between TVOC and CO2 concentrations, for human activity was identified as the primary source of indoor contaminants: peak TVOC concentrations were related to specific household activities such as cooking or leisure. Indoor and outdoor PM2.5 concentrations were likewise observed to be correlated, although not linearly due to the presence of indoor sources. Ventilation as presently practiced in winter appears to be insufficient to dilute indoor contaminants in all three buildings, nor does summertime behavior guarantee air quality.

Bad Air Can Also Kill: Residential Indoor Air Quality and Pollutant Exposure Risk during the COVID-19 Crisis

“…Since relatively high extreme values were found in all dwellings, although only occasionally, the value of the median was more appropriate than the average for representing the behavior of the indoor environment, as the latter is more affected by the presence of extreme values. Excluding CS 1, the medians, both prior to and during confinement, were within the typical findings of similar contemporary dwellings [ 42 ], although these were higher than desirable and far from healthy environments. The representative values were within the acceptable label atmospheres, but their high variability, with a variation coefficient of 38.5% to 93.89% for the pre-COVID period and 58.95% to 109.88% for the confinement, indicates periods with high or very high levels of contaminant concentration that became more frequent during confinement.…”

“…In general, the dwellings started with an acceptable air renewal situation as the CO 2 profiles indicate, except for CS2. Typical values are usually below the threshold of 1000 ppm for those found in dwellings of a similar type [ 42 ]. Median values ranged from 696.1 (single-occupant) to 844.3 ppm (five-occupant).…”

“…The at-home confinement situation produced evident alterations in the environmental quality of the dwellings. Starting from typical stock conditions for this type of home [ 42 , 114 ], the confinement increased the exposure conditions, in most of the cases, and, when abnormal starting conditions were present (as in CS1), they worsened. Although this situation was expected, the results should arouse concern in most cases, with the identification of multi-factorial risk factors: VOC and PM concentrations, ventilation strategies and effectiveness, continuous inhabitant presence, and a lack of inhabitant awareness of IAQ as well as other aspects not yet identified but linked with ineffective ventilation.…”

“…Detailed information on the characteristics of the measurement equipment is in Appendix A . Thermal ambient monitoring was conducted in accordance with ISO7726:1998 specifications (ISO/TC 159/SC 5, 1998), both in terms of the instrumentation and methods [ 42 ]. The system was in continuous operation during both time periods.…”

“…There are numerous studies on indoor quality and sick building syndromes, especially in cold countries [ 36 , 37 , 38 , 39 , 40 , 41 ], but studies in temperate areas of Southern Europe are limited, with some studies in operational housing conditions [ 42 , 43 , 44 , 45 , 46 , 47 ]. Studies of the indoor air quality in homes during the COVID 19 lockdown are also limited, although some studies point to household cleaning products as a particularly relevant source of indoor pollution.…”