Supply-chain problems stemming from the COVID-19 pandemic caused limited supplies of filtering facepiece respirators such as N95 masks. Yet strategies to decontaminate personal protective equipment (PPE) remain unresolved in many hospitals with limited resources, both in the United States and abroad.

Researchers have devised a system for decontaminating N95 masks using off-the-shelf materials available at any hardware store combined with ultraviolet type C (UV-C) lights found in shuttered research laboratories. The method offers comparable decontamination to more expensive methods at an affordable cost of about $50 in materials.

UV-C light is routinely used for sterilization of various materials and equipment found in research labs. The technique was repurposed to decontaminate specialized masks for front-line workers in a low-cost, scalable way.

Ultraviolet germicidal irradiation (UVGI) has been validated as an effective method to decontaminate masks between use. UVGI systems are routinely used to decontaminate work environments and surgical suites, equipment, and ambulances but not all healthcare facilities have access to this expensive commercial sterilization equipment. Many UV-C bulbs are sitting idle in biosafety cabinets in university labs and research facilities that may be empty due to restrictions arising from the pandemic.

The system modifies common fluorescent light fixtures to hold and power the specialized UVGI light bulbs. That — in addition to specific light placement arrangements and tin foil-covered cardboard for reflectors — creates multiple decontamination arrangements. To confirm the UV-C lights were effective, the researchers performed mathematical calculations and modeling to make sure the intensity of UV radiation that the repurposed lights emit was correct and the N95 masks received the correct UV exposure to decontaminate the masks.

The research team created a sloped surface to help align masks situated along the edge of the system toward the light source for more uniform decontamination across the surface. (University of Delaware)

The team developed freely downloadable build instructions in simple, easy-to-understand language. The directions emphasize UV safety and focus on use in healthcare because of the need for specialized equipment like a UV-C intensity meter. They also include precautions to measure UV-C intensity to ensure confidence the system is delivering the correct degree of UV intensity for enough time to decontaminate.

The instructions include information on how far apart to space the masks for maximum effectiveness. This is critical because placing them too close together can create shadows that prevent comprehensive UV-C decontamination.

The system is not an at-home device. Users need proper personal protective equipment to work with UV light, which can disrupt DNA and pose safety concerns. This disruptive feature, however, is what makes the UV-C light useful for decontaminating PPE.

The researchers concede that mask reuse is not ideal but they also recognize that not all hospitals or other patient care facilities are equipped with enough PPE to meet demand in a crisis, so first responders may be required to reuse masks in emergency situations. This includes doctors, nurses, and emergency response personnel but also extends to staff who may be cleaning, disinfecting, or preparing spaces for patient care. Beyond hospitals, PPE is worn in residential facilities and rural clinics around the globe that may have limited access to resources.

For more information, contact Andrea Boyle Tippett at This email address is being protected from spambots. You need JavaScript enabled to view it.; 302-831-1421.


Tech Briefs Magazine

This article first appeared in the January, 2021 issue of Tech Briefs Magazine.

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