Thermal-optical coupling and germicidal assessment of in-duct UV-C systems
*Correspondence to:
Hui An, Engineering Cluster, Singapore Institute of Technology, Singapore 828608, Singapore.
E-mail: hui.an@singaporetech.edu.sg
J Build Des Environ. 2026;4:202619. 10.70401/jbde.2026.0043
Received: April 28, 2026Accepted: August 12, 2026Published: August 12, 2026
This manuscript is made available in its unedited form to allow early access to the
reported findings. Further editing will be completed before final publication. As
such,
the content may include errors, and standard legal disclaimers are applicable.
Abstract
Ultraviolet germicidal irradiation (UVGI) is widely applied in heating, ventilation, and air-conditioning systems to reduce airborne pathogen transmission, yet its effectiveness depends on airflow-driven changes in lamp thermal condition and particle residence time. This study experimentally characterises the coupled thermal and optical performance of 95 W and 60 W low-pressure mercury UV-C lamps and uses the measured irradiance fields for comparative germicidal assessment. Air velocities of 1.1-2.5 m/s and ambient temperatures of 14-22 °C were varied to quantify their effects on lamp-surface temperature and 254 nm output. The 95 W lamp maintained near-maximum output over a broader operating range, whereas the 60 W lamp was more sensitive to convective cooling. Reynolds and Rayleigh numbers ranged from approximately to and to, respectively, while the convection-to-radiation heat-loss ratio increased with airflow velocity. Mean modelled UV dose increased with lamp count and decreased with airflow velocity. At 1.1 m/s, six-lamp arrays delivered mean modelled doses of approximately 191 J/m² for the 95 W lamps and 146 J/m² for the 60 W lamps. Published UV susceptibility constants produced calculated reductions exceeding 6 log for susceptible viral and bacterial species, whereas the calculated reductions for Aspergillus spores ranged from below 0.05 to approximately 0.4 log. These microbial reductions were calculated from the measured irradiance fields and published susceptibility constants and were not experimentally validated using bioaerosols. The results provide a measurement-informed basis for comparing lamp power, airflow condition, and lamp arrangement in in-duct UVGI systems.
Keywords
UVGIM, HVAC, irradiance, lamp thermal performance, lagrangian dose, airborne disinfection
References
-
1. Rajput TS, Thomas A. Analyzing the effects of passive design strategies on building ventilation performance and thermal comfort using simulation-based approach. E3S Web Conf. 2023;396:02023.[DOI]
-
2. Oladokun MO, Ali M, Osman SB, Samsuddin N, Hamzah HA. Experimental investigation of ventilation efficiency in a dentistry surgical room. MATEC Web Conf. 2016;66:00115.[DOI]
-
4. Abbaspour A, Seraj H, Bahadori-Jahromi A, Janbey A. Performance of ventilation, filtration, and upper-room UVGI in mitigating PM2.5 and SARS-CoV-2 levels. Clean Technol. 2025;7(3):53.[DOI]
-
5. Tellier R, Li Y, Cowling BJ, Tang JW. Recognition of aerosol transmission of infectious agents: A commentary. BMC Infect Dis. 2019;19(1):101.[DOI]
-
9. Shamim JA, Hsu WL, Daiguji H. Review of component designs for post-COVID-19 HVAC systems: Possibilities and challenges. Heliyon. 2022;8(3):e09001.[DOI]
-
10. Bei W, Mortazavi R, Haghighat F. Evaluation of modeling and measurement techniques of ultraviolet germicidal irradiation effectiveness: Towards the design of immune buildings. Indoor Built Environ. 2009;18(2):101-112.[DOI]
-
11. Ye J, Wargocki P, Ai Z. Modelling of radiation and flow fields in in-duct ultraviolet germicidal irradiation systems with and without ribs. Indoor Built Environ. 2025;34(2):302-318.[DOI]
-
13. Tseng CC, Li CS. Inactivation of virus-containing aerosols by ultraviolet germicidal irradiation. Aerosol Sci Technol. 2005;39(12):1136-1142.[DOI]
-
15. American Society of Heating, Refrigerating and Air-Conditioning Engineers. Germicidal ultraviolet lamp systems. In: 2024 ASHRAE handbook-HVAC systems and equipment. Peachtree Corner: American Society of Heating, Refrigerating and Air-Conditioning Engineers. 2024. Available from: https://www.ashrae.org/technical-resources/ashrae-handbook/description-ashrae-handbook-hvac-systems-and-equipment?utm_source=chatgpt.com
-
17. Commission Internationale de l'Éclairage. Ultraviolet air disinfection. Vienna: Commission Internationale de l'Éclairage. 2003. Available from: https://www.cie.co.at/publications/ultraviolet-air-disinfection?utm_source=chatgpt.com
-
18. VanOsdell D, Foarde K. Defining the effectiveness of UV lamps installed in circulating air ductwork. Arlington (VA): Air-Conditioning and Refrigeration Technology Institute; 2002.[DOI]
-
19. Li Z, Ma X, Liao Y. Combined performance of upper-room UVGI and ceiling-mounted air cleaners for removing active bioaerosol. Build Environ. 2025;267:112230.[DOI]
-
20. McDonagh A, Noakes CJ, Fletcher LA. Experimentally evaluating the effectiveness of an upper-room UVGI system. In: Proceeding of the 11th REHVA World Congress CLIMA 2013-Energy Efficient, Smart and Healthy Buildings; 2013 Jun 16-19; Prague, Czech Republic. Prague: REHV; 2013. Available from: https://eprints.whiterose.ac.uk/id/eprint/79035/
-
21. Noakes CJ, Sleigh PA, Fletcher LA, Beggs CB. Use of CFD modelling to optimise the design of upper-room UVGI disinfection systems for ventilated rooms. Indoor Built Environ. 2006;15(4):347-356.[DOI]
-
22. Yang Y, Lai ACK, Wu C. Study on the disinfection efficiency of multiple upper-room ultraviolet germicidal fixtures system on airborne microorganisms. Build Environ. 2016;103:99-110.[DOI]
-
25. Kowalski W. Ultraviolet germicidal irradiation handbook: UVGI for air and surface disinfection. 1st ed. Heidelberg: Springer;2009:[DOI]
-
26. Lau J, Bahnfleth W, Freihaut J. Estimating the effects of ambient conditions on the performance of UVGI air cleaners. Build Environ. 2009;44(7):1362-1370.[DOI]
-
27. Cattai F, D’Orazio A, Sbardella G. A systematic review on the application of ultraviolet germicidal irradiation to HVAC systems. Energies. 2023;16(22):7569.[DOI]
-
29. Li Y, Chen X, Wang Y, Zhang Y. Effects of environmental factors, measurement and modeling for germicidal efficiency of in-duct ultraviolet germicidal irradiation system. Energy Built Environ. 2025;6(5):826-833.[DOI]
-
30. Schmalwieser AW, Hirschmann G, Cabaj A, Sommer R. Method to determine the power efficiency of UV disinfection plants and its application to low pressure plants for drinking water. Water Supply. 2017;17(4):947-957.[DOI]
-
31. Bolton J, Santelli M. Method for measurement of the output of monochromatic (254 nm) low pressure UV lamps. IUVA News. 2008;19(1). Avauilable from:https://violegen.com/media/Method-for-the-Measurement.pdf
-
32. Lee B, Bahnfleth WP. Effects of installation location on performance and economics of in-duct ultraviolet germicidal irradiation systems for air disinfection. Build Environ. 2013;67:193-201.[DOI]
-
33. Scheir R, Fencl FB. Using UVC technology to enhance IAQ. Heat Piping Air Cond. 1996;68:109. Available from: https://www.semanticscholar.org/paper/Using-UVC-technology-to-enhance-IAQ-Scheir-Fencl/69f7f267e7ca42cb432c207b92f6cdcca761e10a
-
34. Bolton JR, Linden KG. Standardization of methods for fluence (UV dose) determination in bench-scale UV experiments. J Environ Eng. 2003;129(3):209-215.[DOI]
-
35. Bolton J, Santelli M. Method for the measurement of the output of monochromatic (254 nm). IUVA News.2008;19(1):9-16. Available from: https://violegen.com/media/Method-for-the-Measurement.pdf
-
36. Spectrecology. Maya2000Pro spectrometer: data sheet. 2020. Available from: https://spectrecology.com/wp-content/uploads/2020/11/Maya2000Pro-Data-Sheet.pdf?utm_source=chatgpt.com
-
37. National Institute of Standards and Technology (NIST). Strong lines of mercury (Hg). In: Handbook of basic atomic spectroscopic data. Gaithersburg (MD): National Institute of Standards and Technology; 2025. Available from: https://physics.nist.gov/PhysRefData/Handbook/Tables/mercurytable2.htm?utm_source=chatgpt.com
-
38. Babaee H, Perdikaris P, Chryssostomidis C, Karniadakis GE. Multi-fidelity modelling of mixed convection based on experimental correlations and numerical simulations. J Fluid Mech. 2016;809:895-917.[DOI]
-
39. Balaji C, Hölling M, Herwig H. A general methodology for treating mixed convection problems using asymptotic computational fluid dynamics (ACFD). Int Commun Heat Mass Transf. 2007;34(6):682-691.[DOI]
-
40. Churchill SW, Usagi R. A general expression for the correlation of rates of transfer and other phenomena. AIChE J. 1972;18(6):1121-1128.[DOI]
-
41. McKay MD, Beckman RJ, Conover WJ. Comparison of three methods for selecting values of input variables in the analysis of output from a computer code. Technometrics. 1979;21(2):239-245.[DOI]
-
46. Huang PY, Shi ZY, Chen CH, Den W, Huang HM, Tsai JJ. Airborne and surface-bound microbial contamination in two intensive care units of a medical center in central Taiwan. Aerosol Air Qual Res. 2013;13(3):1060-1069.[DOI]
-
48. Baltussen TJH, Zoll J, Verweij PE, Melchers WJG. Molecular mechanisms of conidial germination in Aspergillus spp. Microbiol Mol Biol Rev. 2020;84(1):e00049-e00019.[DOI]
-
49. Blachowicz A, Raffa N, Bok JW, Choera T, Knox B, Lim FY, et al. Contributions of spore secondary metabolites to UV-C protection and virulence vary in different aspergillus fumigatus strains. mBio. 2020;11(1):e03415-e03419.[DOI]
-
51. Firrantello J, Bahnfleth W. Field measurement and modeling of UVC cooling coil irradiation for heating, ventilating, and air conditioning energy use reduction (RP-1738)—Part 2: Energy, indoor air quality, and economic modeling. Sci Technol Built Environ. 2018;24(6):600-611.[DOI]
Copyright
© The Author(s) 2026. This is an Open Access article licensed under a Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, sharing, adaptation, distribution and reproduction in any medium or format, for any purpose, even commercially, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Publisher’s Note
Science Exploration remains a neutral stance on jurisdictional claims in published
maps
and institutional affiliations. The views expressed in this article are solely those
of
the author(s) and do not reflect the opinions of the Editors or the publisher.
Share And Cite
Science Exploration Style
Kanagalingam S, An H, Fong YM, Soh CB, Chien SC, Wang PC, et al. Thermal-optical coupling and germicidal assessment of in-duct UV-C systems. J Build Des Environ. 2026;4:202619. https://doi.org/10.70401/jbde.2026.0043
Tips
Copy completed.
Submit a Manuscript
Author Instructions
Cite this Article
Article Metrics
0
View
0
Download
Cited
Article Updates
Get citation
Science Exploration Style
Kanagalingam S, An H, Fong YM, Soh CB, Chien SC, Wang PC, et al. Thermal-optical coupling and germicidal assessment of in-duct UV-C systems. J Build Des Environ. 2026;4:202619. https://doi.org/10.70401/jbde.2026.0043
copy
Share Link
copy