What question did this study set out to answer?

This research aims to predict key indoor air quality parameters based on spatial factors, occupant behaviors, and external conditions in urban residences.

June 6, 2026Open Access

Predicting multiple indoor air quality parameters from spatial factors, occupant behaviours, and external conditions in single-zone urban residential units: a case study in Bangkok

TKThanyatorn KhumpairojTokyo Metropolitan University MIMasayuki IchinoseTokyo Metropolitan University KCKittiwoot ChaloeytoyChulalongkorn University

Key Points

This research aims to predict key indoor air quality parameters based on spatial factors, occupant behaviors, and external conditions in urban residences.
Field data were collected from 30 single-zone studio apartments through continuous IAQ monitoring and occupant behavior logs.
Tracer gas decay tests were conducted to assess ventilation efficiency.
Models analyzed to classify high- and low-risk scenarios for indoor air quality parameters.
Keeping windows closed while using air conditioning maintains acceptable temperature and PM 2.5 levels, but CO₂ accumulates during higher occupancy periods.
Opening windows reduces CO₂ levels but raises risks of overheating and humidity, especially in winter due to high outdoor PM 2.5.
Nighttime during the rainy season is identified as a favorable period for safe and energy-efficient natural ventilation.

Abstract

Indoor Air Quality (IAQ) plays a crucial role in safeguarding occupant health and comfort, particularly in compact urban residences that lack dedicated mechanical ventilation systems and rely instead on occupant-driven ventilation practices and outdoor environmental conditions. In large tropical cities such as Bangkok, this challenge is further intensified by deteriorating outdoor air pollution, rising temperatures, and shifting indoor activity patterns in the post-pandemic era. This study introduces an integrated diagnostic framework to predict the risk of exceedance of four key IAQ parameters—temperature, relative humidity (RH), carbon dioxide (CO₂), and fine particulate matter (PM 2.5 )—based on spatial factors, real-life occupant behaviors and external climatic conditions. Field data were collected from 30 single-zone studio apartments through continuous IAQ monitoring, tracer gas decay tests, and occupant behavior logs. Analyzed models were applied to quantify the influence of different factors and classify high- and low-risk scenarios. The results indicate that keeping windows closed while operating air conditioners and air purifiers effectively maintains acceptable indoor temperature and PM 2.5 levels; however, CO₂ accumulates during periods of higher occupancy, highlighting the need for supplemental outdoor air intake. Conversely, window opening helps reduce CO₂ concentration but elevates risks of overheating, excessive humidity, and PM 2.5 exposure—particularly during the winter season when outdoor PM 2.5 levels are high. Nonetheless, nighttime during the rainy season emerges as the most favorable period for safe and energy-efficient natural ventilation. These findings provide essential empirical evidence to inform building design and operational practices, guide policy interventions, and establish a data foundation for developing adaptive ventilation strategies to sustainably improve IAQ in tropical urban environments.

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