Indoor Air Quality (IAQ) research within educational institutions assumes a critical role due to its multifaceted significance (Mushtaha and Helmy, 2017; Jung and Awad, 2021a; Awad and Jung, 2021; Jung and Al Qassimi, 2022). It prioritizes students’ and staff’s health and wellbeing (Maghrabie et al., 2021; Awad and Jung, 2022). Inadequate IAQ poses detrimental consequences, particularly for vulnerable occupants like children, who exhibit heightened susceptibility to indoor pollutants (Kelly and Fussell, 2019; Jung and El Samanoudy, 2023; Jung et al., 2021a). Consequently, extensive research endeavors play a pivotal role in identifying pollutant sources and associated health risks, thereby facilitating the implementation of effective measures to safeguard the wellbeing of individuals (Becerra et al., 2020; Campagnolo et al., 2017). Secondly, IAQ research significantly contributes to academic performance and productivity (Mohamed et al., 2021; Brink et al., 2021; Jia et al., 2021). Empirical studies have unequivocally established that substandard IAQ engenders symptoms that impede concentration and cognitive function, subsequently impinging upon academic achievements (Majd et al., 2019; Asif et al., 2018). Consequently, dedicated research efforts to enhance IAQ become imperative for cultivating a conducive learning environment (Jung and Awad, 2021b). Thirdly, IAQ research is crucial in optimizing energy efficiency and augmenting building performance (Arar et al., 2022). A direct relationship exists among academic performance, energy efficiency, compliance with standards, and cost savings, as each factor reinforces the others in a well-maintained indoor environment (Makaremi et al., 2024). Improved IAQ through efficient ventilation and filtration enhances student concentration and academic outcomes by reducing symptoms of poor air quality, such as fatigue and respiratory issues (Toyinbo, 2023). When aligned with IAQ standards, energy-efficient systems can lower operational costs by reducing excessive energy usage while ensuring regulatory compliance. Adhering to IAQ standards minimizes potential health-related expenses for schools, resulting in long-term cost savings through fewer student absences, lower maintenance requirements, and optimized resource allocation. This interconnected approach fosters a healthier, more productive, and cost-effective educational environment. Achieving an optimal equilibrium entails meticulous management of ventilation rates, accurate control of pollutant sources, and the strategic implementation of efficient filtration systems, all collectively enhancing IAQ while minimizing energy consumption (Arar and Jung, 2022; Jung et al., 2021b; Jung et al., 2021c). Through research investigations, viable strategies to strike this delicate balance can be discerned, fostering energy conservation and facilitating the development of sustainable school infrastructure (Jung and Awad, 2023; Mahmoud et al., 2023). Additionally, IAQ research is invaluable in ensuring compliance with pertinent legal and regulatory standards (Ndou and Aigbavboa, 2023; Jung and Abdelaziz Mahmoud, 2023). A comprehensive understanding of these requirements proves pivotal in safeguarding the health and wellbeing of occupants while averting potential legal entanglements (Abdelaziz Mahmoud and Jung, 2023). Finally, investments in IAQ research yield substantial long-term cost savings by curbing health-related absences, amplifying productivity levels, and potentially reducing maintenance expenses (Mushtaha et al., 2021; Jung et al., 2022a). Overall, the significance of IAQ research in educational settings is indisputable, as it effectively cultivates healthier and more productive learning environments, benefitting both students and staff (Li and Yu, 2022; Jung and Mahmoud, 2022).

Between 2013 and 2014, the Public Health and Safety Department of Dubai Municipality evaluated IAQ comprehensively in 70 educational institutions, including universities, schools, nurseries, kindergartens, and healthcare centers (Mushtaha et al., 2020; Dubai Municipality, 2023; Al Qassimi and Jung, 2022). This initiative seeks to implement globally recognized benchmarks for the internal environment while ensuring their alignment with the specific local context of Dubai (Jung et al., 2021d; Jung et al., 2022b). The overarching objective is cultivating a healthy cityscape with a pollutant-free atmosphere (Jung and Arar, 2023). The study emphasizes segments of the population most vulnerable to the detrimental effects of substandard IAQ, including children of all ages, individuals with underlying health conditions, and the elderly (Hwang et al., 2018; Kelly and Fussell, 2019; Mushtaha et al., 2022). Motivated by the observations of numerous healthcare organizations, which indicate that indoor pollutant levels can surpass those found outdoors, the initiative acknowledges that a significant portion of people spend up to 90% of their time indoors (Cincinelli and Martellini, 2017; Liu et al., 2020).

The study aims to measure indoor pollution levels, identify sources of contamination, and propose effective strategies aimed at mitigating and reducing the concentration of indoor pollutants (Widder and Haselbach, 2017). This assessment served as the basis for establishing stringent IAQ regulations by Dubai Municipality (Kakoulli et al., 2022). These regulations stipulate that formaldehyde (HCHO) levels should not exceed 0.08 ppm (parts per million), Total Volatile Organic Compound (TVOC) levels should be below 300 μg/m³, and suspended particulates (PM₁₀) should not exceed 150 μg/m³ during continuous monitoring for 8 h before occupancy (Amoatey et al., 2018). Despite these rigorous IAQ standards set for childcare facilities, adherence to these standards is lacking in practice (Vardoulakis et al., 2020). Failure to meet these IAQ standards not only hampers learning efficiency among infants and children but also gives rise to significant symptoms of Sick Building Syndrome (SBS), including respiratory ailments, nausea, eye irritation, drowsiness, and potential long-term health complications (Samudro et al., 2022; Hussien et al., 2023a).

This study presents the empirical findings obtained from an investigation conducted in December 2022, focusing on the indoor environment of three school buildings in Dubai. The study aims to provide crucial measurement data about indoor air pollutants within school premises, explicitly concerning their potential impact on students during their formative years, encompassing infancy and adolescence. By offering tangible measurement data derived from assessments conducted in school buildings, this study fills an existing void in the absence of comprehensive empirical data.

Furthermore, this study aims to delineate the current IAQ standard established by the Dubai Municipality. By furnishing foundational data for subsequent investigations, this study strives to identify the prevailing contamination levels in school environments and undertake a comparative analysis vis-à-vis the IAQ standards promulgated by the World Health Organization (WHO). Such a comparative assessment contributes to a comprehensive understanding of the IAQ landscape while guiding future research endeavors.

Sick Building Syndrome (SBS), primarily from HCHO and VOCs emitted by building materials, has gained significant attention as a research area in the last decade (Ismaeel et al., 2022; Liu et al., 2022; D’Amico et al., 2020). Symptoms associated with SBS include irritation of the eyes, nose, and throat, headaches, fatigue, difficulty concentrating, and occasionally dizziness, nausea, and chest tightness (Teiri et al., 2021; Arar and Jung, 2021). Table 1 provides an overview of the effects of each hazardous substance on the human body (Hussien et al., 2023b).

Table 2 presents WHO’s IAQ standards, outlining their comprehensive regulations (Mikola et al., 2022). These standards not only adhere to the guidelines set by the WHO but also provide detailed specifications based on the duration of exposure (Parkinson et al., 2019; McArthur and Powell, 2020).

The measurement results offer significant insights into the IAQ within the surveyed classrooms of three international schools in Dubai. Specific sources of pollutants identified in this study likely include building materials, furnishings, and electronic equipment, each contributing different types of VOCs and formaldehyde. For example, furniture adhesives and synthetic materials in seating and flooring can emit VOCs continuously, while electronic equipment in computer labs contributes to higher TVOC levels during operational hours. Environmental factors such as ventilation rates, temperature, and humidity also play a crucial role in influencing these pollutant levels, with higher emissions often observed under warmer and more humid conditions or in poorly ventilated spaces. Based on these findings, several strategies can be proposed to improve IAQ in educational settings. Implementing advanced ventilation systems with real-time monitoring, selecting low-emission materials for future renovations, and maintaining consistent temperature and humidity control are essential. Additionally, adopting regular cleaning protocols with low-VOC cleaning agents and scheduling periodic IAQ assessments can further help maintain healthy indoor environments. Future studies focusing on the emission rates of specific materials in controlled environments could further inform these strategies and enhance their effectiveness.

The average values derived from the comprehensive measurements conducted in December 2022 indicate that certain pollutants, including TVOC, total airborne bacteria, and noise levels, surpassed the prescribed maintenance standards. Conversely, the measurements for other pollutants remained within acceptable limits, meeting the requisite standards. The evaluation of TVOC revealed a wide range of concentrations, with the highest recorded value reaching 1584.0 μg/m³, signifying the peak TVOC concentration observed. In contrast, the lowest recorded value was 437.2 μg/m³, representing the minimum TVOC concentration detected. The average concentration, denoted by the mean value of 780.8 μg/m³, provides a comprehensive overview of the TVOC levels across the surveyed classrooms. The standard deviation of 306.1 reflects the extent of variability in TVOC concentrations. Regarding HCHO, the maximum recorded value was 135.8 μg/m³, while the minimum was 7.8 μg/m³. The average concentration, indicated by the mean value of 40.0 μg/m³, represents the typical HCHO levels measured. The standard deviation of 38.2 signifies the extent of variability in HCHO concentrations. Analysis of the TBC revealed a maximum recorded value of 5256.0 CFU/m³, indicating the highest count of total airborne bacteria observed. Conversely, the minimum recorded value amounted to 202.0 CFU/m³, representing the lowest bacterial count detected. The mean value of 2176.4 CFU/m³ presents the average count of bacteria across the surveyed classrooms, while the standard deviation of 1995.8 reflects the variability in TBC measurements. The measurement results for CO₂ exhibited a maximum recorded value of 1712.4 ppm, whereas the minimum value recorded was 540.2 ppm. The average concentration, represented by the mean value of 811.0 ppm, signifies the typical CO₂ levels measured. The standard deviation of 278.8 indicates the degree of variability in CO₂ concentrations.

Comparing the measurement results for TVOC and HCHO across different classroom types, it is evident that TVOC levels surpassed the WHO standard of 400 μg/m³, even in buildings older than 5 years. The science lab demonstrated approximately 14% higher TVOC levels than the classroom, while the computer lab exhibited about 70% higher levels. In contrast, the concentrations of HCHO remained within the standard limit of 100 μg/m³, with higher levels detected in the science labs compared to the classrooms and computer labs. The concentrations of VOCs, such as Benzene, Toluene, Ethylbenzene, and Xylene, were significantly lower than the WHO-recommended IAQ standards. When comparing the measured values, relatively higher concentrations were observed in the computer lab compared to the classroom. Benzene was the only substance exhibiting moderately elevated levels in the science lab. Elevated benzene levels, specifically in the science lab, may be attributed to chemical reagents or lab materials containing benzene, commonly used in certain laboratory activities. Additionally, the restricted ventilation typical in lab settings can lead to localized accumulation, thus exceeding WHO standards.

Analyzing the measurements based on class sessions revealed that TVOC and HCHO measurements exhibited higher values during class sessions. This correlation among TVOC, formaldehyde, airborne bacteria, CO, and CO₂ likely stems from increased occupancy and activity during class hours, which elevate emissions from human respiration, body odors, and materials within the classroom (Nandan et al., 2021). Formaldehyde and TVOC emissions can also increase due to interactions with body heat and friction against classroom surfaces, such as desks and floors. Additionally, limited classroom ventilation may lead to localized accumulation of these substances, further explaining the observed correlation. Conversely, VOC substances like Benzene, Toluene, Ethylbenzene, and Xylene consistently demonstrated elevated measured values when classes were not in session. This pattern suggests that these pollutants may originate from continuous building materials and furnishings emissions (Poirier et al., 2021). Many construction materials, such as adhesives, sealants, synthetic resins, and certain types of paint, are known to release VOCs over extended periods through off-gassing. This process is influenced by factors such as temperature and humidity, which can enhance emissions in closed environments when windows and doors are shut, as is typical during non-class hours. Future research could focus on identifying specific materials responsible for elevated VOC levels and assessing how these emissions vary over time and with environmental conditions. Such studies would offer valuable insights into material-specific contributions to indoor air quality issues and guide the selection of low-emission materials in school environments. The elevated levels of these substances during non-class periods may be attributed to off-gassing from building materials, furnishings, and cleaning products, which continue to release VOCs even in the absence of occupants. Additionally, limited ventilation during non-class hours, as windows and doors are often kept closed, may contribute to the buildup of these substances in the indoor air (Sadrizadeh et al., 2022). NO₂ levels also tend to rise during non-class periods, likely due to reduced ventilation, allowing any residual emissions from outdoor sources or internal equipment to accumulate (Salonen et al., 2019). Airborne bacteria, CO, CO₂, and radon levels were higher during class sessions, while NO₂ levels were higher when classes were not in session. The observed increase in NO₂ levels during non-class periods likely originates from indoor sources rather than outdoor emissions. Combustion-based equipment, such as gas stoves, heating systems, or laboratory burners, may contribute to these levels. This is consistent with findings that NO₂ emissions from indoor sources can accumulate in poorly ventilated environments when windows and doors are closed. While reduced ventilation during non-class periods may limit the inflow of outdoor NO₂, it can exacerbate the accumulation of NO₂ from indoor sources due to limited air exchange. Further investigation into the presence and use of combustion-based equipment in these spaces is necessary to confirm this hypothesis.

Considering the temporal changes in the target school building, the concentrations of TVOC, HCHO, and other substances generally displayed a decreasing trend ranging from 18% to 65%. However, it is worth noting that even in buildings older than 5 years, the levels of TVOC occasionally exceeded the WHO standard of 400 μg/m³.

These findings offer valuable insights into the IAQ levels in school environments in Dubai. As this study is based on a limited sample of schools within a specific region, the results primarily serve as a case study. They may not fully capture the variability of IAQ across different geographical locations, building designs, or operational practices. Future studies should incorporate a larger, more diverse sample to allow for statistical generalization and support broader conclusions. Comparative studies across different climates, building types, and ventilation systems would provide more robust data on IAQ trends in educational environments. Additionally, longitudinal studies could help determine how IAQ evolves in response to changes in building materials, occupancy patterns, and maintenance practices. By comparing the measurements against established IAQ standards, this study contributes to a comprehensive understanding of the current IAQ landscape and guides future research endeavors. The results emphasize the significance of monitoring and maintaining proper IAQ in schools to ensure a healthy and conducive learning environment for students and teachers. Monitoring and maintaining adequate IAQ in educational institutions is crucial for fostering a healthy learning environment. Poor IAQ can negatively impact students’ health, concentration, and cognitive performance, ultimately affecting academic outcomes. Regular monitoring allows administrators to promptly identify and address IAQ issues, reducing health risks and enhancing comfort for students and staff. Implementing systematic IAQ management practices, including scheduled ventilation checks, use of low-emission materials, and periodic air quality assessments, can help ensure that educational spaces remain safe, conducive to learning, and aligned with health standards. By prioritizing IAQ, educational institutions can contribute to students’ wellbeing and academic success.

A total of 18 classrooms were measured in three international schools during winter in Dubai in December 2022. The measurement results were analyzed based on overall averages, classroom types, class presence, and the secular change of the school buildings. The summary of the measurement results is as follows:

The average air quality measurements across all classrooms revealed that TVOC and airborne bacteria exceeded the standards set by the WHO. While these findings are significant for understanding IAQ in Dubai’s educational institutions, they are limited by the study’s scope as a case study. Broader, multi-regional studies are necessary to confirm whether the observed IAQ patterns hold in diverse educational settings and climates. Such expanded research could enhance these conclusions’ applicability, offering generalizable policy insights across various contexts. Additionally, noise levels surpassed the recommended limits. Other contaminants, besides TVOC and HCHO, were detected at lower levels that did not meet the maintenance standards. However, in the science or computer labs, these contaminants were measured at least 15% and up to 70% higher than in general classrooms.

When comparing the measurement results during class and non-class periods for general classrooms (excluding science labs and computer labs), it was found that TVOC, HCHO, airborne bacteria (TBC), CO, CO₂, and other substances showed higher measured values during class sessions. On the other hand, Benzene, Toluene, Ethylbenzene, Xylene, and NO₂ exhibited higher measured values when classes were not in session.

Notably, TVOC levels were generally higher during class sessions, while Benzene, Toluene, Ethylbenzene, Xylene, and other substances exhibited higher average measurement values during non-class periods. This contrasts with the expectation that substances like Benzene and Toluene, which are components of TVOC, would also show higher levels during class sessions. It can be inferred that undetected VOCs other than Ethylbenzene and Xylene are relatively high during classes with more students.

These results suggest that pollutants from general organic chemical products, such as student clothing or school supplies, may contribute to the observed levels. Further investigation and analysis of various substances among TVOC components in future studies would provide valuable insights.

Benzene and Toluene, commonly found in building materials, may contribute to the higher levels detected during non-class periods. The increased amount of pollutants leaked from classroom building materials could be attributed to the closure of doors and external windows during non-class periods.

Comparing the pollutant measurements based on the secular changes in schools constructed less than 5 years ago and schools built more than 5 years ago, it was observed that TVOC, HCHO, Benzene, Toluene, Ethylbenzene, and Xylene displayed a tendency to decrease by an average of 18%–65% in schools older than 5 years.

It is important to note that the measurements were conducted during Dubai’s winter, which was characterized by high classroom temperatures and humidity. The results should be considered in light of the natural ventilation occurring through the opening and closing doors and windows.

The measurements of TVOC and airborne bacteria, encompassing various volatile organic compounds, exceeded the legally recommended standards and maintenance standards for indoor air quality management as outlined by the WHO.

These results indicate that despite the significant natural ventilation mentioned earlier, the indoor air quality in the measured schools during December did not maintain a favorable environment.

To enhance indoor air quality (IAQ) in educational institutions, policymakers and school administrators should focus on several key strategies. Improving ventilation systems is essential, especially in science and computer labs with elevated VOC levels. Advanced filtration and ventilation enhancements can help control pollutant levels during occupied and unoccupied hours. Regular IAQ monitoring and transparent reporting can enable prompt responses to air quality concerns, helping maintain healthy environments aligned with WHO and local standards. Prioritizing low-emission building materials and furniture, especially during renovations, will mitigate long-term VOC emissions and improve overall IAQ. Additionally, using low-emission cleaning agents and scheduling cleaning during non-peak occupancy hours can further prevent pollutant accumulation. Awareness and training programs for staff and students can foster proactive IAQ management behaviors, reinforcing a commitment to health and safety. These recommendations provide practical steps for creating healthier and more conducive learning environments that support wellbeing and academic success.

Moreover, the varying composition ratios of indoor pollutants in different classrooms within the same school, such as science labs and computer labs, indicate the need for different ventilation standards for these specialized classrooms. Further investigation is warranted to study the emission characteristics of other individual volatile organic compounds included in TVOC, apart from Ethylbenzene and Xylene, by analyzing pollutants during class and non-class periods. Specific ventilation standards should be considered for general and special-purpose classrooms like science and computer labs.