Indoor air quality (IAQ) significantly impacts human health, particularly in enclosed spaces where people spend most of their time. This study evaluates the performance of low-cost IAQ sensors, focusing on their ability to measure carbon dioxide (CO₂) and particulate matter (PM) under real-world conditions. Measurements provided by these sensors were verified against calibrated reference equipment. The study utilized two commercial devices from inBiot and Kaiterra, comparing their outputs to a reference sensor across a range of CO₂ concentrations (500–1200 ppm) and environmental conditions (21–25 °C, 27–92% RH). Data were analyzed for relative error, temporal stability, and reproducibility. Results indicate strong correlation between low-cost sensors (LCSs) and the reference sensor at lower CO₂ concentrations, with minor deviations at higher levels. Environmental conditions had minimal impact on sensor performance, highlighting robustness to temperature and humidity within the tested ranges. For PM measurements, low-cost sensors effectively tracked trends, but inaccuracies increased with particle concentration. Overall, these findings support the feasibility of using low-cost sensors for non-critical IAQ monitoring, offering an affordable alternative for tracking CO₂ and PM trends. Additionally, LCSs can assess long-term exposure to contaminants, providing insights into potential health risks and useful information for non-expert users.

Indoor air quality (IAQ) is influenced by a wide range of chemical, biological and physical agents that can negatively impact physical, immunological and mental health. Adverse health effects depend on the type and concentration of pollutants, duration of exposure, and individual susceptibility. The availability of data on IAQ is limited, as are standardized approaches for evaluating its health impact. This expert review aims to describe the most important indoor air determinants affecting health, and present the IDEAL cluster, which comprises seven EU‐funded scientific projects on the topic of IAQ and human health. Across the IDEAL projects, knowledge is generated on exposure to a wide range of indoor air pollutants, including well‐known hazards and more explorative chemical and microbiological determinants. The projects will also contribute to the implementation of low‐cost and/or real‐time sensors on IAQ, as well as advanced chemical and microbiological analyses, and evaluate various interventions to improve IAQ. Several of them focus on particularly vulnerable groups. Raising public awareness and implementing measures to reduce pollutant levels are essential for safeguarding health, particularly in urban areas with elevated pollution levels.

Identifying tobacco smoke exposure in indoor environments is critical for public health, especially in vulnerable populations. In this study, we developed and validated a machine learning model to detect smoking households based on indoor air quality (IAQ) data collected using low-cost sensors. A dataset of 129 homes in Spain and Austria was analyzed, with variables including PM_2.5, PM₁, CO₂, temperature, humidity, and total VOCs. The final model, based on the XGBoost algorithm, achieved near-perfect household-level classification (100% accuracy in the test set and AUC = 0.96 in external validation). Analysis of PM_2.5 temporal profiles in representative households helped interpret model performance and highlighted cases where model predictions revealed inconsistencies in self-reported smoking status. These findings support the use of sensor-based approaches for behavioral inference and exposure assessment in residential settings. The proposed method could be extended to other indoor pollution sources and may contribute to risk communication, health-oriented interventions, and policy development, provided that ethical principles such as transparency and informed consent are upheld.

NDOOR AIR QUALITY ASSESSMENT IN A HIGHER EDUCATION LIBRARY: IMPLICATIONS FOR ENVIRONMENTAL QUALITY IN EDUCATIONAL SPACES Brisa Braga,, Ermelinda Pereira, Susana Capitão, Fabiana Tiago, Paula Baptista, Manuel Feliciano HIGH-RESOLUTION MONITORING OF HYGROTHERMAL AND INDOOR AIR QUALITY: ARE MEDITERRANEAN SCHOOLS HEALTHY? Carmen María Calama-González Jesús Llanos-Jiménez; Rocío Escandón; Rafael Suárez INTELLIGENT LOW-COST MONITORS FOR INDOOR AIR QUALITY MONITORING IN SCHOOLS Hiten Chojer ; J.P. Sá,; P.T.B.S Branco,; F.G. Martins,; S.I.V. Sousa, HIGH SCHOOL STUDENTS’ RESEARCH ON ENERGY EFFICIENCY AND ENVIRONMENTAL QUALITY IN A SECONDARY SCHOOL BUILDING Miguel Díaz Sofía Zaragoza METHODOLOGY FOR CHARACTERISING INDOOR AIR QUALITY IN EUROPEAN SCHOOLS USING CONTINUOUS MONITORING AND GO-AQS INDICATORS Jose Fermoso; Sandra Rodríguez-Sufuentes; Alicia Aguado; Artur Badyda; Adam Muszynski; Piotr Kepa, Mariusz Rogulski, Alexandra Kristian CHILDREN’S RIGHTS TO SAFE, HEALTHY AND SUSTAINABLE EDUCATIONAL BUILDINGS IN SPAIN Enrique Hernández-Diez; Margherita Mini and Claudia Ponce de León Rodríguez URBAN CLASSROOMS AS POLLUTION AMPLIFIERS: FULL-YEAR EXPERIMENTAL EVIDENCE Alberto Leal Matilla; Alicia Zaragoza Benzal; Alexandra Míguez Souto; Daniel Ferrández Vega E+V MORE VENTILATED SCHOOLS: IMPROVING THE IAQ OF EDUCATIONAL CENTERS Fabian López Plazas; Eva Crespo Sánchez; Mònica Ubalde-López; Gloria Carrasco-Turigas; Silvia Gómez Araujo; Pablo Gonzalez Ruiz ENHANCING LEARNING ENVIRONMENTS THROUGH ADDITIONAL ACOUSTIC METRICS INTEGRATING IEQ PERSPECTIVES Juan Negreira; Nicolás Bermejo-Presa; Isabel Sánchez-Camacho ASSESSMENT OF INDOOR ENVIRONMENTAL QUALITY (IEQ) UNDER EPBD 2024 IN A ZERO EMISSION BUILDING. CASE STUDY Julio San José-Alonso, ; Yolanda Arroyo, ; Francisco J. Rey-Martínez, Luis J. San José-Gallego,; Alberto Rey ; Carmen A. García-García , and Javier M. Rey-Hernández ,. CITIZEN SCIENCE TO UNDERSTAND CHILDREN’S THERMAL COMFORT AND HEAT ADAPTATION PRACTICES AT SCHOOL Mar Satorras; Joana Ortiz; Carlos Chang; Elena Domene ENVIRONMENTAL MONITORING THROUGH IOT AND DIGITAL TWINS: A FRAMEWORK FOR INTELLIGENT BUILDING MAINTENANCE STRATEGIES Carmen Gómez, Francisco Castilla, Alejandro Lucas and Antonio Adán EVALUATING NATURE-BASED SOLUTIONS IN EDUCATIONAL ENVIRONMENTS: A METHODOLOGICAL MATRIX FOR EUROPEAN CASE STUDIES Hugo Canahua LIGHT AND TRANSPARENCY AS ENVIRONMENTAL VALUE. THREE EDUCATIONAL FACILITIES DESIGNED BY TRAZA ARQUITECTURA Francisco Felipe Muñoz Carabias; Manuel Rodrigo Gutiérrez de la Cámara FROM GIANT REED WASTE TO HEALTHY CLASSROOMS: LIME BASED ARUNDO DONAX L. PANELS FOR LOW EMISSION INTERIORS Jonathan Ruiz-Jaramillo; Carmen M. Muñoz-González; Ana Morales-Guisande; Milagrosa Borrallo-Jiménez

Selecting interior wood materials requires balancing functional and aesthetic demands with indoor air quality, as wood can emit volatile organic compounds (VOCs) and very volatile organic compounds (VVOCs) that either peak shortly after installation or persist over time. This study investigated time-resolved VOC and VVOC accumulation concentrations from untreated pine, spruce, aspen, and oak, representing wood species commonly used in Norway. Concentrations of VOCs and VVOCs were monitored for 25–28 days under low-ventilation, worst-case chamber conditions using Proton Transfer Reaction–Time-of-Flight Mass Spectrometry (PTR-TOF-MS). Emission behaviour was assessed using peak concentration, decay rate, half-time, stabilised concentration, cumulative exposure (AUC₂₈), and available health-based thresholds. Clear species-dependent differences were observed. Pine was the dominant VOC source, with the highest peak concentration, stabilised concentration, and AUC₂₈, mainly due to monoterpenes, which remained above the health-based threshold throughout the test period. Oak showed the second-highest VOC burden and a distinct acetate-dominated profile, with acetic acid showing the longest predicted exceedance duration. Aspen and spruce had lower VOC burdens, but their cumulative VVOC exposure exceeded VOC exposure. VVOCs generally peaked earlier than VOCs, although persistence varied by species. Overall, the concentration of VOCs and VVOCs was controlled by species, compound chemistry, volatility, and internal transport, supporting species- and compound-specific ventilation and material-selection strategies.