Occupancy Implications on Indoor Air Quality (IAQ) in Selected Primary School Classrooms Around Kuantan, Pahang

Authors: Hazrin AH, Maryam Z, Hizrri A, Norhidayah A, Samsuddin N, Mohd Shukri MA

Affiliations: International Islamic University Malaysia; Universiti Malaysia Pahang

Published: Malaysian Journal of Public Health Medicine, 2017, Special Volume (1): 94–105

Last reviewed: March 2026

Background and Context

Children spend a substantial proportion of their waking hours inside school buildings, making the indoor environment of classrooms a critical determinant of respiratory health and overall well-being. Research has consistently demonstrated that children are more vulnerable to indoor air pollutants than adults: their higher respiratory rates relative to body weight mean they inhale proportionately greater volumes of air, and their developing respiratory and immune systems are more susceptible to the effects of airborne contaminants. Poor indoor air quality in schools has been associated with increased rates of absenteeism, reduced cognitive performance, diminished learning productivity, and the development or exacerbation of respiratory conditions including asthma, allergic rhinitis, and upper respiratory tract infections.

The indoor air quality of school buildings is influenced by a complex interplay of factors including building design and ventilation characteristics, outdoor air quality, cleaning and maintenance practices, building materials and furnishings, and — critically — the number and activities of occupants. In naturally ventilated school buildings, which are the predominant building type in tropical Malaysian settings, the occupancy factor takes on particular significance. Each occupant contributes to the indoor pollutant load through metabolic CO₂ production, bioaerosol emission (including bacteria and fungal spores shed from skin, clothing, and the respiratory tract), and resuspension of settled particulate matter through movement and activity.

Malaysia’s tropical climate creates additional challenges for maintaining acceptable IAQ in schools. High ambient temperatures and humidity levels can promote the growth and dispersal of biological contaminants, while the prevalence of natural ventilation — through open windows and doors — means that outdoor pollutant sources, including traffic emissions and regional haze episodes, can directly impact indoor air quality. The Department of Occupational Safety and Health (DOSH) Malaysia has established the Industry Code of Practice on Indoor Air Quality (ICOP-IAQ) which sets acceptable limits for various IAQ parameters, providing a regulatory framework for assessing indoor environments.

Study Design and Methodology

This study employed a comparative design, measuring selected IAQ parameters inside primary school classrooms during two contrasting conditions: occupied periods (during regular school hours on weekdays when students were present) and non-occupied periods (during weekends when classrooms were empty). This paired comparison approach enabled the researchers to isolate the specific contribution of occupancy to indoor pollutant levels while controlling for other building and environmental factors that remained constant between the two measurement periods.

Physical and chemical IAQ parameters were assessed using a DustMate Environmental Dust Detector for particulate matter measurements (PM₁₀ and PM₂.₅) and a VelociCalc Multi-Function Ventilation Meter 9565 for carbon dioxide concentration and temperature measurements. Both instruments are established tools in IAQ assessment, capable of continuous real-time monitoring. Measurements were recorded at 30-minute intervals over 8-hour monitoring sessions at designated sampling points within the classrooms.

Biological contaminants were assessed through air sampling for airborne bacteria and fungi, with results expressed as colony forming units per cubic metre of air (CFU/m³). The sampling methodology employed culture-based techniques that capture viable airborne microorganisms, providing a measure of the biologically active component of indoor bioaerosol exposure.

Findings and Analysis

The results demonstrated a clear and consistent pattern: all measured IAQ parameters showed elevated levels during occupied periods compared to non-occupied periods. Carbon dioxide concentrations rose substantially when students were present, reflecting the cumulative metabolic output of 30 to 40 children in a confined classroom space. In naturally ventilated tropical classrooms, CO₂ levels serve as a practical proxy indicator for overall ventilation adequacy — elevated CO₂ concentrations indicate that the rate of fresh air exchange is insufficient to dilute occupant-generated pollutants.

Particulate matter concentrations were similarly elevated during occupied periods. The resuspension of settled dust through children’s movement — walking, sitting, standing, and general classroom activity — is a well-documented contributor to indoor PM levels. In Malaysian school settings, factors such as uncarpeted concrete or tile floors, chalk or whiteboard marker use, and the transport of outdoor soil and dust on footwear further contribute to the particulate matter burden.

Biological contaminant levels showed pronounced increases during occupancy, with both bacterial and fungal CFU counts rising significantly. Human occupants are a primary source of indoor bioaerosols, shedding bacteria from skin and clothing and exhaling respiratory microorganisms. In tropical environments with warm temperatures and high humidity, conditions are additionally conducive to fungal growth on building surfaces and furnishings, with occupant activity contributing to the aerosolisation of fungal spores.

IAQ Parameters: Occupied vs Non-Occupied Classrooms

Implications for School Building Design and Management

The findings carry practical implications for the design and management of primary school buildings in Malaysia. Ventilation adequacy is the primary modifiable factor for managing occupancy-related IAQ degradation. In naturally ventilated buildings, this translates to ensuring sufficient window and door openings, appropriate building orientation to capture prevailing breezes, and avoiding overcrowding that exceeds the ventilation capacity of the classroom space. Where natural ventilation is insufficient, mechanical ventilation or hybrid systems may be warranted.

Classroom occupancy management — maintaining appropriate student-to-classroom ratios — is a direct intervention point. The Malaysian Education Ministry’s guidelines on class size, combined with building design standards, should account for the IAQ implications of high-density occupancy in tropical settings. Regular cleaning protocols, particularly wet mopping to minimise dust resuspension, and the maintenance of building envelope integrity to manage moisture ingress and fungal growth, represent cost-effective measures for improving biological IAQ.

Limitations

The study was conducted at selected schools in the Kuantan area of Pahang, and findings may not be generalisable to schools in other climate zones or with different building designs within Malaysia. The measurement periods, while providing valuable comparative data, represent snapshots that may not capture the full range of temporal variation in IAQ. Seasonal factors, including the annual haze season affecting Peninsular Malaysia, were not specifically addressed. The study measured airborne microbial load through culture-based methods, which detect only viable organisms and may underestimate total bioaerosol exposure.