Low-cost sensors for indoor air quality monitoring: A systematic review of accuracy, applications, and limitations

Indoor air quality significantly influences public health, especially due to prolonged indoor time. Low-cost sensors (LCSes) have emerged as promising tools for indoor air quality (IAQ) monitoring in real-life environments. This systematic review evaluates the accuracy, applications, and limitations of LCSes for monitoring indoor pollutants, focusing on particulate matter and carbon dioxide. Following the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020 guidelines, a systematic search was conducted in PubMed, Scopus, and ScienceDirect databases for studies published up to March 15, 2025. Eligible studies included original peer-reviewed research evaluating the accuracy, performance, and applicability of low-cost sensors for indoor air quality monitoring in real-world settings. The focus was on studies measuring carbon dioxide and/or particulate matter and comparing the performance of low-cost sensors against reference-grade instruments. The quality and risk of bias of included studies were assessed using the Critical Review Form for Quantitative Studies. Of the 2,736 articles initially identified, 24 studies met the inclusion and quality criteria. These studies evaluate a wide range of low-cost sensor technologies for indoor air quality monitoring, particularly for particule matter and carbon dioxide. The majority of sensors used optical particle counters or nondispersive infrared technology and were validated against reference-grade instruments. Results demonstrate that several low-cost sensors achieved strong correlations with reference monitors, particularly under controlled or semicontrolled conditions. However, performance varied significantly based on environmental factors such as humidity, temperature, and pollutant source. Limitations include methodological heterogeneity, limited interdevice validation, regional bias, insufficient legal compliance assessment, and unaddressed confounding factors such as sensor aging and environmental cross-sensitivity. Low-cost sensors offer a valuable, scalable approach for IAQ monitoring in diverse environments. Despite variability in performance, with appropriate calibration and environmental compensation, many LCSes can provide reliable data. Yet, standardization in validation procedures and sensor regulation is crucial for their integration into legal and health-related frameworks.<i>Implications</i>: This systematic review demonstrates that low-cost sensors hold significant potential to enhance indoor air quality monitoring in schools, workplaces, health care facilities, and homes. However, the majority of currently available devices do not yet meet government standards or legal compliance requirements, and their data must therefore be interpreted with caution. While some models show promise and can provide reliable results under controlled conditions or with appropriate calibration, their broader adoption for public health purposes will require standardized validation protocols and stronger regulatory frameworks. Aligning technological performance with legal and health standards is essential to ensure trustworthy data, equitable access to air quality information, and meaningful reductions in indoor pollutant exposure.