Indoor air quality is an important factor in maintaining a healthy living environment. In this study, indoor particulate matter concentrations (PM₁, PM₂.₅ and PM₁₀) were monitored in a residential living room in Bengaluru, India which is naturally ventilated, using a low-cost SmileDrive air quality sensor. Measurements were taken at hourly intervals over three consecutive days from 18 to 20 March 2025, along with temperature and relative humidity. The results showed that particulate matter concentrations varied throughout the day, with PM₁₀ recording higher values than PM₂.₅ and PM₁. The daily mean concentrations ranged from 10.47–12.24 µg m⁻³ for PM₁, 14.26–16.76 µg m⁻³ for PM₂.₅, and 16.21–19.24 µg m⁻³ for PM₁₀. Overall, the measured concentrations indicated relatively good indoor air quality during the monitoring period. Temperature and relative humidity also showed normal daily fluctuations. An analysis of the relationship between relative humidity and particulate matter concentrations revealed that the strength of the correlation varied across the three days, with stronger associations observed on 19 and 20 March 2025. The study demonstrates that low-cost sensors can be effectively used for short-term indoor air quality monitoring and can give useful information on the behaviour of particulate matter in residential environments.

Keywords: Indoor Air Quality, Low-Cost Sensors, Particulate Matter, Relative Humidity (RH), Correlation, Temperature, PM Concentration, Naturally Ventilated, Monitoring, Residential Environment.

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Source of Funding:

This study did not receive any grant from funding agencies in the public, commercial, or not–for–profit sectors.

Competing Interests Statement:

The authors declare no competing interests.

Consent for publication:

The authors declare that they consented to the publication of this study.

Authors' contributions:

Both the authors conceptualized the study, performed data analysis, and prepared the manuscript.

Availability of data and materials:

Authors are willing to share data and material on request.

Ethical Approval:

Not applicable for this study.

Institutional Review Board Statement:

Not applicable for this study.