The interest and use of immersive UV-C technologies has increased dramatically as a response to the SARS-CoV-2 pandemic1,2. Immersive UV-C technologies use germicidal light to disinfect shared spaces or high-touch objects to reduce transmission of communicable illnesses. The SARS-CoV-2 pandemic exposed the need for safer shared spaces and the need for effective tools for reducing the viral load on high touch surfaces 3–6. UV-C disinfection is well understood in the water industry for biological control and in healthcare settings for upper airway germicidal irradiation7. UV-C disinfection is considered an adjunct cleaning method to reduce the instance of hospital acquired infections (HAIs) via drug resistant organisms 8,9. Donning and doffing of personal protective equipment (PPE) in healthcare settings has been identified as a viral vector in several studies 10,11. UV-C disinfection of pathogen bearing clothing has the potential to reduce the instance of hospital acquired infections and can have uses for high traffic settings such as office buildings, stadiums, and university campuses 4,12.
The dynamics of non-porous materials are well understood from a UV-C perspective whereas there exists a knowledge gap in applying immersive UV-C technologies to porous materials. One study investigated the efficacy of chemical disinfectants on porous and non-porous surfaces and demonstrated that textiles, such as cotton, were less efficient for disinfection by 2-log when compared to disinfection glass surfaces 13. Understanding both the micro and macro-geometry of porous materials have significant implications for the efficacy of UV-C disinfection and must be considered when disinfecting complex surfaces 6,14−16. For example, immersive UV-C technologies were used for emergency front facing respirator (FFR) reuse, where studies have shown FFR material type is instrumental in UV-C disinfection efficacy and governs the upper limit of achievable disinfection 1,6,16,17. To the authors knowledge, there is no published study that investigates the efficacy of immersive UV-C disinfection on common, porous materials such as cotton. The importance of this knowledge gap is magnified when considering the growing interest to disinfect shared spaces, which consist of a mixture of porous and non-porous materials.
Disinfection cabinets are an immersive UV-C technology, which have been brought to market for several niche applications, such as clothing retailers, locker rooms, and laboratories. Disinfection cabinets provide 360o of UV-C exposure, which maximizes the illuminated area on porous objects and reduces the impact of shadowing. Another important factor to consider for these technologies is light distribution. Improper distribution of UV-C light can lead to inadequate disinfection of targeted objects. There are several tools that can be used to characterize the fluence delivered by immersive UV-C light sources such as UV-C dosimeter cards, biodosimetry, and spectroradiometry. Given the novelty of immersive UV-C devices, no standard exists for quantifying 360o fluences. This paper addresses this issue by characterizing a UV-C disinfection cabinet using common challenge microorganisms and radiometric techniques. Biodosimetry, chemical dosimetry (via dosimeter cards), and spectroradiometry were all used to characterize fluence using cotton T-shirts as the challenge garment. Cotton fabric is commonly found in clothing, furniture, and across all settings for UV-C applications and serves as a surrogate for porous materials. The outcomes of this study inform both the healthcare and UV-C industry regarding best practices when considering the disinfection of porous materials.