Assessment of Indoor Air Quality in Selected Residential Buildings of Kathmandu Using Low-Cost PM2.5 Monitoring and Occupant Perception Survey

Abstract

Indoor air quality (IAQ) has become a critical environmental health concern, particularly in rapidly urbanizing cities where outdoor pollution infiltrates residential environments. This study assessed indoor air quality in selected residential buildings in the Gyaneshwor area of Kathmandu Valley using a low-cost PM2.5 sensor combined with an occupant questionnaire survey. Real-time measurements of PM2.5 concentration, temperature, and relative humidity were conducted in kitchens and living rooms of four residential houses over seven consecutive days during winter. A structured questionnaire survey involving 15 occupants were conducted to examine awareness of air quality, ventilation practices, and health symptoms related to indoor exposure. The results showed that indoor PM2.5 concentrations frequently exceeded the health-based guideline value of 15 µg/m³ recommended by the World Health Organization, with levels often exceeding 100 µg/m³. Higher concentrations were consistently observed in kitchens compared to living rooms, indicating the influence of indoor activities such as cooking. Survey findings revealed low awareness of the Air Quality Index (AQI) and limited preventive practices, despite a high prevalence of symptoms such as headache, cough, and fatigue among occupants. The study highlights that residential indoor environments in Kathmandu may not provide adequate protection from particulate pollution and emphasizes the need for improved ventilation strategies, public awareness, and policy attention to indoor air quality.