Humans spend the majority of their time indoors, where they are potentially exposed to hazardous pollutants. Within this context, over the past few years, there has been an upsurge of low-cost sensors (LCS) for the measurement of indoor air pollutants, motivated both by recent technological advances and by increased awareness of indoor air quality (IAQ) and its potential negative health impacts. Although not meeting the performance requirements for reference regulatory-equivalent monitoring indoors, LCS can provide informative measurements, offering an opportunity for high-resolution monitoring, emission source identification, exposure mitigation and managing IAQ and energy efficiency, among others. This article discusses the strengths and limitations that LCS offer for applications in the field of IAQ monitoring; it provides an overview of existing sensor technologies and gives recommendations for different indoor applications, considering their performance in the complex indoor environment and discussing future trends.

Indoor air quality (IAQ) in educational facilities is crucial due to the extended time students spend in those environments, affecting their health, academic performance, and attendance. This paper aimed to review relevant parameters (building characteristics and factors related with occupancy and activities) for assessing IAQ in educational facilities, and to identify the parameters to consider when performing an IAQ monitoring campaign in schools. It also intended to identify literature gaps and suggest future research directions. A narrative literature review was conducted, focusing on seven key parameters: building location, layout and construction materials, ventilation and air cleaning systems, finishing materials, occupant demographics, occupancy, and activities. The findings revealed that carbon dioxide (CO₂) levels were predominantly influenced by classroom occupancy and ventilation rates, while particulate matter (PM) concentrations were significantly influenced by the building's location, design, and occupant activities. Furthermore, this review highlighted the presence of other pollutants, such as trace metals, polycyclic aromatic hydrocarbons (PAHs), carbon monoxide (CO), nitrogen dioxide (NO₂), ozone (O₃), and radon, linking them to specific factors within the school environment. Different IAQ patterns, and consequently different parameters, were observed in various school areas, including classrooms, canteens, gymnasiums, computer rooms, and laboratories. While substantial literature exists on IAQ in schools, significant gaps still remain. This study highlighted the need for more studies in middle and high schools, as well as in other indoor microenvironments within educational settings beyond classrooms. Additionally, it underscored the need for comprehensive exposure assessments, long-term studies, and the impacts of new materials on IAQ including the effects of secondary reactions on surfaces. Seasonal variations and the implications of emerging technologies were also identified as requiring further investigation. Addressing those gaps through targeted research and considering the most updated standards and guidelines for IAQ, could lead to define more effective strategies for improving IAQ and safeguarding the students' health and performance.