Evaluation of the microbiological indoor air quality at a commercial building in Muscat, Oman, utilizing an all-air multi-zone HVAC system

Muthuraman Subbiah; Sivaraj Murugan; Kumar Ayyappan

doi:10.59400/be2478

Evaluation of the microbiological indoor air quality at a commercial building in Muscat, Oman, utilizing an all-air multi-zone HVAC system

Muthuraman Subbiah
Department of Engineering, University of Technology and Applied Sciences, Muscat 133, Oman
Sivaraj Murugan
Department of Mechanical Engineering, Cochin University of Science and Technology, Kochi 682022, India
Kumar Ayyappan
Department of Applied Sciences, Amrita College of Engineering and Technology, Erachakulam 629902, India

Article ID: 2478

DOI: https://doi.org/10.59400/be2478

Keywords: bacteria, fungi, indoor air quality, HVAC device, commercial building

Abstract

This study evaluates the microbiological indoor air quality (IAQ) of a commercial office building in Muscat, Oman, equipped with an all-air multi-zone heating, ventilation, and air-conditioning (HVAC) system operating under hot-arid climatic conditions. Active air sampling was conducted at multiple locations, including open-plan offices, outdoor air intake, supply air diffusers, fan coil units, and the humidification water tank of the air handling unit (AHU), across different seasons. Airborne bacteria were analyzed using incubation at 22 ℃ and 37 ℃ to distinguish environmental and human-associated microbial populations, while fungal concentrations were assessed at 25 ℃, with results expressed as colony-forming units per cubic meter (CFU/m³). For analytical consistency, data from the three office spaces investigated were aggregated and evaluated as seasonal averages. Bacterial concentrations in indoor air generally ranged from 32 to 496 CFU/m³ at 37 ℃ and 4 to 500 CFU/m³ at 22 ℃, indicating low to moderate contamination levels under normal operating conditions. In contrast, a pronounced increase in fungal concentrations was observed during the initial winter sampling, exceeding 2000 CFU/m³, which was attributed to an exceptional flooding event. Comparative analysis of outdoor air, AHU-treated air, and indoor air demonstrated that the HVAC system effectively reduced microbial loads during standard climatic conditions. The findings provide region-specific baseline data on microbiological IAQ and highlight the influence of HVAC operation, seasonal variation, and extreme environmental events on indoor bioaerosol levels in commercial buildings located in hot-arid climates.

Published

2025-07-13

How to Cite

Subbiah, M., Murugan, S., & Ayyappan, K. (2025). Evaluation of the microbiological indoor air quality at a commercial building in Muscat, Oman, utilizing an all-air multi-zone HVAC system. Building Engineering, 3(3). https://doi.org/10.59400/be2478

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Vol. 3 No. 3 (2025)

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Article

This work is licensed under a Creative Commons Attribution 4.0 International License.

References

[1]Zhao R, Guo L, Qi J, et al. Indoor and outdoor bioaerosol distributions and concentration profiles during different seasons and pollution events in Qingdao city. Building and Environment. 2025; 279: 113056.

[2]Kauch K, Brągoszewska E, Mainka A. Microbiological air quality in healthcare environments: A review of selected facilities. Applied Sciences. 2025; 15(16): 8976.

[3]Kumar P, Singh R. Microbial indoor air pollution in Delhi Metropolitan City and associated health effects. Frontiers in Public Health. 2025; 13: 1626827.

[4]Yusof SK. Bioaerosol concentration and health implications for children in indoor environments. Aerobiologia. 2025; 41: 643–665.

[5]Chamseddine A, Elzein IM, Hassan N. Indoor air quality in critical indoor environments: A review. Water, Air, & Soil Pollution. 2025; 236: 885.

[6]Correia G, Calheiros D, Rosa N, et al. Indoor air quality and airborne transmission under the One Health Lens: A scoping review. One Health. 2025; 21: 101160.

[7]Mannan M, Al-Ghamdi SG. Indoor air quality in buildings: A comprehensive review on the factors influencing air pollution in residential and commercial structure. International Journal of Environmental Research and Public Health. 2021; 18(6): 3276. doi: 10.3390/ijerph18063276

[8]Mata TM, Felgueiras F, Martins AA, et al. Indoor air quality in elderly centers: pollutants emission and health effects. Environments. 2022; 9(7): 86. doi: 10.3390/environments9070086

[9]Niza IL, de Souza MP, da Luz IM, et al. Sick building syndrome and its impacts on health, well-being and productivity: A systematic literature review. Indoor and Built Environment. 2024; 33(2): 218–236. doi: 10.1177/1420326X231191079

[10]Saad SM, Shakaff AYM, Saad ARM, et al. Development of indoor environmental index: Air quality index and thermal comfort index. AIP Conference Proceedings. 2017; 1808(1): 020043.

[11]Sadrizadeh S, Yao R, Yuan F, et al. Indoor air quality and health in schools: A critical review for developing the roadmap for the future school environment. Journal of Building Engineering. 2022; 57: 104908. doi: 10.1016/j.jobe.2022.104908

[12]Saffell J, Nehr S. Improving indoor air quality through standardization. Standards. 2023; 3(3): 240–267. doi: 10.3390/standards3030019

[13]Singh MK, Ooka R, Rijal HB, et al. Progress in thermal comfort studies in classrooms over last 50 years and way forward. Energy and Buildings. 2019; 188–189: 149–174. doi: 10.1016/j.enbuild.2019.01.051

[14]Technical assistance document for the reporting of daily air quality—The Air Quality Index (AQI). Available online: https://www.airnow.gov/sites/default/files/2020-05/aqi-technical-assistance-document-sept2018.pdf (accessed on 18 December 2024).

[15]Air quality guidelines global update 2005: Particulate matter, ozone, nitrogen dioxide and sulfur dioxide. Available online: https://www.who.int/publications/i/item/WHO-SDE-PHE-OEH-06.02 (accessed on 15 October 2024).

[16]9 out of 10 people worldwide breathe polluted air, but more countries are taking action. Available online: https://www.who.int/ar/news/item/16-08-1439-9-out-of-10-people-worldwide-breathe-polluted-air-but-more-countries-are-taking-action (accessed on 15 October 2024).

[17]Zhang D, Ortiz MA, Bluyssen PM. Clustering of Dutch school children based on their preferences and needs of the indoor environmental quality in classrooms. Building and Environment. 2019; 147: 258–266. doi: 10.1016/j.buildenv.2018.10.014

[18]Law AKY, Chau CK, Chan GYS. Characteristics of bioaerosol profile in office buildings in Hong Kong. Building and Environment. 2001; 36: 527–541. doi: 10.1016/S0360-1323(00)00020-2

[19]Pasanen AL, Niininen M, Kalliokoski P, et al. Airborne Cladosporium and other fungi in damp versus reference residences. Atmospheric Environment. 1992; 26: 121–124.

[20]Pastuszka JS, Paw UKT, Lis DO, et al. Bacterial and fungal aerosol in indoor environment in Upper Silesia, Poland. Atmospheric Environment. 2000; 34: 3833–3842. doi: 10.1016/S1352-2310(99)00527-0

[21]Ali WAAI, Ibrahim A. The problem of air pollution in the cities of Sixth of October and Obour. Arab Geographical Journal. 2023; 54(176): 1–92. (in Arabic)

[22]Ventilation and acceptable indoor air quality. Available online: https://www.ashrae.org/file%20library/technical%20resources/standards%20and%20guidelines/standards%20addenda/62_1_2022_x_20221108.pdf (accessed on 15 December 2024).

[23]Bluyssen PM, Zhang D, Kurvers S, et al. Self-reported health and comfort of school children in 54 classrooms of 21 Dutch school buildings. Building and Environment. 2018; 138: 106–123. doi: 10.1016/j.buildenv.2018.04.032

[24]Dubey S, Rohra H, Taneja A. Assessing effectiveness of air purifiers (HEPA) for controlling indoor particulate pollution. Heliyon. 2021; 7(9): e07976. doi: 10.1016/j.heliyon.2021.e07976

[25]Ebbini GW. Transforming health: The WELL Building Standard’s role in sustainable development. Cell Reports Sustainability. 2024; 1(5): 100100. doi: 10.1016/j.crsus.2024.100100

[26]Law No. 4 of 1994 promulgating the law on the environment, as amended by Law No. 9 of 2009 and the executive regulations. Available online: https://www.eeaa.gov.eg/Laws/55/index (accessed on 15 October 2024). (in Arabic)

[27]Fikry A, Elsayed A. Improving the indoor air quality (IAQ) in naturally ventilated lecture hall with a single facade by solar chimneys. Journal of Engineering and Applied Science. 2021; 68: 18–29. doi: 10.1186/s44147-021-00027-7

[28]Goyal R, Khare M. Indoor–outdoor concentrations of respirable suspended particulate matter in classroom of a naturally ventilated school building near an urban traffic roadway. Atmospheric Environment. 2009; 43(38): 6026–6038. doi: 10.1016/j.atmosenv.2009.08.031

[29]Gul H, Das BK. The impacts of air pollution on human health and well-being: A comprehensive review. Journal of Environmental Impact Management and Policy. 2023; 3(6): 1–11. doi: 10.55529/jeimp.36.1.11

[30]Liu X. ASTM and ASHRAE standards for the assessment of indoor air quality. In: Handbook of Indoor Air Quality. Springer; 2022. pp. 1511–1545.

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