Taken as a whole, the indoor environmental quality (IEQ) is a concept that deals not only with thermal conditions, but it also goes much further, because it includes indoor air quality (IAQ), illuminance or acoustic comfort. Among the different categories of buildings, schools are one of the most important in society especially because future generations are spending more than 6 h/day and ensuring them a healthy and comfortable environment must be top priority. The purposes of this research were to better understand school children’s IEQ preferences and needs in classrooms and to compare these among rural versus urban respondents. To reach this goal, a simple yet complete survey was proposed and, along with measurements, multiple conclusions were made. The methodology proposed was to reach a large sample of respondents to give more credibility and precision to the analysis. The results are based on the responses of 790 occupants both from urban and rural environments. Lack of ventilation, cooling, low or too high temperatures during winter/summer periods and a misappropriate sizing or piloting of the heating system are some of the issues found during the survey. The paper tackles several issues at once, helping to paint a more holistic image of the problems encountered in school classrooms. Optimal thermal comfort is not met during the cold season in any of the schools under investigation. The old rural schools were found to be the worst performing buildings compared to urban schools where due to recent investments in refurbishment the winter thermal comfort was enhanced. During the study, it was observed that one of the major IAQ problems consisted in elevated levels of CO₂ or particulate matter especially for the schools situated in the city. Noise was reported as an issue only for the schools situated next to national roads while visual comfort was found to be acceptable for more than 94% of respondents from all regions.

Air pollution risk factor on human health was surpassed only by high blood pressure, tobacco use and poor diet. Total number of deaths due to air pollution worldwide was estimated to 6.67 million people in 2019. In the European Union, 97% of the urban population is exposed to levels of fine particulate matter above the latest guideline levels set by the World Health Organization. Air pollution accounts for 20% of newborn deaths worldwide, most related to complications of low birth weight and preterm birth. Low birth weight and preterm birth are responsible for 1.8 million deaths worldwide. Bucharest is the capital city of Romania and one of the most polluted cities in Europe, ranking in the 9th position out of 96 of the top cities from Europe and in the 4th position out of 32 of the top cities in Eastern Europe, data from June 2022. The aim of this study was to measure the real time level of indoor particulate pollution levels in different indoor environments from Bucharest, during the pandemic period. The PM_2.5/PM₁₀ ratio and its rate of change were also determined for the measured data. The PM_2.5/PM₁₀ ratio and its rate of change were also calculated based on the measurement data. The PM_2.5/PM₁₀ ratio showed an upward trend on weekends compared to weekdays, suggesting a relationship with outdoor PM where leisure activities and traffic infiltrated the indoors. The fluctuation range of the PM_2.5/PM₁₀ ratio was 0.44~0.95, and low measured values were detected on weekdays. Of the seasons, the proportion of particulate in autumn and its rate of change tended to be higher than in summer. It was suggested that outdoor air may have permeated the room. In addition, the relationship was considered, such as it is a holiday period, there are few rainy days, the concentration of coarse particles is high, and the number of residents in the city decreases. When it comes to indoor air quality, the higher this ratio, the more serious the air pollution. PM₁₀ concentrations decreased by 29.1% in the absence of human activity and increased by 35.1% in the presence of humans. PM_2.5 concentration decreased by 30.3% without human activity and increased by 3.1% with the presence of humans. Certain trends were suggested for the resumption of human activity and an increase in PM_2.5 concentrations. The average relative difference between October 2021, a pandemic period, and October 2022, a post pandemic period, was 64% for PM₁₀ and 47% for PM_2.5. The pandemic period brought a significantly better indoor air quality from the particulate pollution point of view.

The purpose of this article is the assessment of energy efficiency and indoor air quality for a single-family house located in Cluj-Napoca County, Romania. The studied house is meant to be an energy-efficient building with thermal insulation, low U-value windows, and a high efficiency boiler. Increasing the energy efficiency of the house leads to lower indoor air quality, due to lack of natural ventilation. As the experimental campaign regarding indoor air quality revealed, there is a need to find a balance between energy consumption and the quality of the indoor air. To achieve superior indoor air quality, the proposed mitigation systems (decentralized mechanical ventilation with heat recovery combined with a minimally invasive active sub-slab depressurization) have been installed to reduce the high radon level in the dwelling, achieving an energy reduction loss of up to 86%, compared to the traditional natural ventilation of the house. The sub-slab depressurization system was installed in the room with the highest radon level, while the local ventilation system with heat recovery has been installed in the exterior walls of the house. The results have shown significant improvement in the level of radon decreasing the average concentration from 425 to 70 Bq/m³, respectively the carbon dioxide average of the measurements being around 760 ppm. The thermal comfort improves significantly also, by stabilizing the indoor temperature at 21 °C, without any important fluctuations. The installation of this system has led to higher indoor air quality, with low energy costs and significant energy savings compared to conventional ventilation (by opening windows).

Air quality in school environments is of particular interest due to the significant amount of time children spend in these settings. Children, being a particularly sensitive demographic, are exposed to various pollutants at school or kindergarten. In this regard, our studies have focused on monitoring the concentrations of three main categories of pollutants: VOCs (volatile organic compounds), VICs and PM (particulate matter). We conducted two experimental campaigns in seven classrooms within public educational institutions. The average concentration values of TVOC (total volatile organic compounds) ranged from 554 µg/m³ to 2518 µg/m³, of CO₂ from 1055 ppm to 2050 ppm, of NH₃ (Ammonia) from 843.2 µg/m³ to 1403.4 µg/m³, of PM2.5 from 25.1 µg/m³ to 89.9 µg/m³, and of PM10 from 63.7 µg/m³ to 307.4 µg/m³. In most instances, the registered values exceeded the limit values set by national or international regulations. Furthermore, this study highlights the significant impact of a heat recovery ventilation system in improving indoor air quality by substantially reducing the levels of CO₂ and PM. However, it also underscores the need for further measures to more efficiently reduce TVOC concentrations. The aim of our paper was to enhance the understanding of pollution levels in school environments, increase awareness of the importance of indoor air quality, and highlight the adverse effects of polluted air on the health of occupants.