Indoor air quality in schools of a highly polluted south Mediterranean area

Abstract

This study aimed at surveying lower secondary schools in southern Italy, in a highly polluted area. A community close to an industrial area and three villages in rural areas was investigated. Indoor temperature, relative humidity (RH), gaseous pollutants (CO2 and NO2), selected biological pollutants in indoor dust, and the indoor/outdoor mass concentration and elemental composition of PM2.5 were ascertained. Temperature and RH were within, or close to, the comfort range, while CO2 frequently exceeded the threshold of 1000 ppm, indicating inadequate air exchange rate. In all the classrooms, median NO2 levels were above the WHO threshold value. Dermatophagoides p. allergen concentration was below the sensitizing threshold, while high endotoxin levels were detected in the classrooms, suggesting schools may produce significant risks of endotoxin exposure. Concentration and solubility of PM2.5 elements were used to identify the sources of indoor particles. Indoor concentration of most elements was higher than outdoors. Resuspension was responsible for the indoor increase in soil components. For elements from industrial emission (Cd, Co, Ni, Pb, Sb, Tl, V), the indoor concentration depended on penetration from the outside. For these elements, differences in rural vs industrial concentrations were found, suggesting industrial sources may influence indoor air quality nearby schools.

The Effect of Ventilation Strategies on Indoor Air Quality and Energy Consumptions in Classrooms

“…The experimental analyses (tests FRV 1, FRV 2, FRV 3, FRV 4, FRV 5, MA 1, MA 2, MA 3; Section 2.3.1) and the simulations (tests NV, MA EN 1, MV EN 1; Section 2.3.2) adopted to investigate the different ventilation scenarios in the test-classroom were carried out considering the actual crowding index of the classroom, i.e., a living area per student of 2.2 m 2 person −1 . Such crowding index is quite high with respect to the typical values recognized and/or imposed in classrooms [43]. Therefore, in order to analyze the possible effect of the crowding index on the air quality and the energy need, further analyses of the CO 2 concentration trends and required air exchange rate in the classroom were performed considering higher occupant densities: 2 m 2 person −1 (crowding index indicated by the European Committee for Standardization [19]), 1.8 m 2 person −1 (crowding index imposed by the current Italian legislation for primary schools [44]), 1.6 m 2 person −1 (here considered as representative of overcrowded classrooms).…”

“…Nonetheless, such improvement of the indoor air quality related to CO 2 levels lead to higher energy consumptions (as hereinafter reported) and not predictable effects on other pollutants typically present in schools (e.g., ultrafine particles, PM 10 , PM 2.5 , NO x , radon, VOCs, etc.) [24][25][26][27][28]30,43,[70][71][72][73]. In Figure 5 the CO2 concentrations trends estimated through a mass balance equation for the following ventilation scenarios are also reported: i) natural ventilation (n = 0.22 h −1 ; NV), ii) mechanical ventilation with n = 2.76 h −1 (MV EN 1), iii) manual airing with n = 2.76 h −1 (MA EN 1).…”

“…Indeed, the energy need of schools is mostly related to the heating during cold seasons (besides the hot water production) [39], and it was detected that 85% of the Italian school buildings are high energy-demanding buildings as they fall within the three lowest energy performance classes [40]. Nonetheless, even if the air-tightness of the Italian schools is not always adequate, high indoor CO 2 concentrations were detected in classrooms, then showing not sufficient air exchange rates with respect to the CO 2 emission sources (i.e., children) [29,[41][42][43]. This is mainly due to the ventilation strategy typically used in schools, in fact, less than 2% of the Italian schools are equipped with ventilation systems (mechanical ventilation systems or "all-air" heating systems) able to guarantee the minimum ventilation rates required by the standards (http://dati.istruzione.it/opendata/approfondimenti/statistiche).…”

“…This is mainly due to the ventilation strategy typically used in schools, in fact, less than 2% of the Italian schools are equipped with ventilation systems (mechanical ventilation systems or "all-air" heating systems) able to guarantee the minimum ventilation rates required by the standards (http://dati.istruzione.it/opendata/approfondimenti/statistiche). This issue is even more important in overcrowded classrooms characterized by occupant densities [43] higher than those imposed by European standards and national regulations [19,44]. Nonetheless, even though the ventilation methods adopted in schools can play a significant role to handle simultaneously the energy consumption and indoor air quality issues [45], few data on the combined effect of the ventilation approach on both indoor air quality and energy saving are available so far.…”

Carbon Dioxide Human Gains—A New Approach of the Estimation

“…As underlined by Lu et al, [6], the concentration of CO 2 in office buildings is primarily dependent on occupant density and ventilation rates. It is worth noting that CO 2 concentration is often found above recommendations in buildings with high people density and insufficient ventilation, especially schools [10][11][12][13][14][15][16][17]. Problems with CO 2 concentration in residential buildings were discussed by Mainka et al, [18].Nowadays, the ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers) standard [19] recommends indoor CO 2 concentrations less than 700 ppm above the outdoor concentration, giving also a guideline of 1000 ppm.…”