Seasonal relationship between particulate matter and bacteria at typical locations of HVAC system in campus buildings—a case study

Zhao, Yu, Wang, Kangning, Wang, Yuhan, Xiong, Chang, Li, Yinqi, Luo, Zhiwen ORCID: https://orcid.org/0000-0002-2082-3958 and Zheng, Hong 2026. Seasonal relationship between particulate matter and bacteria at typical locations of HVAC system in campus buildings—a case study. Indoor Air 2026 (1) , 2851043. 10.1155/ina/2851043

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Abstract

The hygiene condition of campus HVAC systems significantly affects the health of students and faculty. In this study, field measurements were conducted in the HVAC systems of a university library and office building during summer and winter. The objectives were to investigate the seasonal distribution characteristics of particulate matter (PM) and culturable bacterial concentrations in fresh-air intakes, supply-air outlets, and return-air inlets; quantify the correlation between PM and bacterial concentrations; and establish mathematical models for predicting bacterial concentrations based on PM measurements under specific seasonal and operational conditions. These models provide theoretical guidance for the precise and dynamic operation of HVAC equipment and filtration and disinfection systems. The results showed that although all indoor air bacterial concentrations complied with standard limits, the bacterial concentrations in the HVAC systems exceeded the standards at some measurement points. Specifically, 30.00% of the measurement points in the library and 16.67% of those in the office exceeded the bacterial concentration standard in summer. In winter, 33.33% of the measurement points in the office were noncompliant, whereas bacterial concentrations in the library remained below the standard. A significant positive monotonic correlation was found between bacteria and PM of different size fractions in fresh air. A prediction model for the bacterial concentration based on PM10 in fresh air was established as follows: BCF = 490.67 × ln(1.28 × CPMF) + 98.13 T − 71.20 RH (R2 = 0.84), where BCF is the bacterial concentration in fresh air (CFU/m3), and CPMF is the PM10 concentration in fresh air (μg/m3). T and RH are the temperature (°C) and relative humidity, respectively. A prediction equation was also established for return air in summer as follows: mathematical equation+179.80 (R2 = 0.95), where BCR is the bacterial concentration in return air (CFU/m3), and CPMR is the PM10 concentration in return air (μg/m3). However, no significant correlation was found for supply air. As a case study, these findings provide a theoretical reference for the design, operation, and maintenance of HVAC systems in similar campus buildings, thereby contributing to improved indoor air quality and occupant health in such environments. Furthermore, the results highlight the critical importance of the regular maintenance of HVAC systems in indoor spaces with high occupancy similar to those investigated in this study to reduce bacterial contamination and ensure a safer and healthier indoor environment.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Schools > Architecture
Publisher:	Wiley
ISSN:	0905-6947
Date of First Compliant Deposit:	7 July 2026
Date of Acceptance:	10 June 2026
Last Modified:	07 Jul 2026 09:45
URI:	https://orca.cardiff.ac.uk/id/eprint/187992

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