In brief

One promising way to decontaminate and reuse disposable masks is by spraying them with vapourised hydrogen peroxide.

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What’s the best way to reuse an N95 mask?

24 May 2022

By identifying the best way to decontaminate N95 masks, A*STAR scientists are helping solve the environmental consequences of disposable masks.

Previously confined to hospitals and research labs, N95 masks have now become a common sight. While masks have been crucial in reducing the spread of COVID-19, some experts have raised concerns about the amount of waste generated by disposable single-use masks.

While researchers work on developing reusable masks, another potential solution is to decontaminate used masks so that they can be worn again. However, most existing studies on mask decontamination methods have focused on lab-scale or home-use decontaminators, which are too small to handle the large number of masks that places like hospitals go through.

“To be better prepared for any future emergencies, we should continue to assess and design more effective decontamination methods,” said Xian Jun Loh, Executive Director at A*STAR’s Institute of Materials Research and Engineering (IMRE).

To this end, Loh and his team of researchers sought to identify which of the existing methods were most effective and feasible across different modes of use—from small-scale home use to large-scale industrial applications.

Loh’s study focused on two popular decontamination methods: subjecting the masks to UV rays or spraying them with vapourised hydrogen peroxide (VHP). Because both UV and VHP decontamination can work on large batches of masks at once, they are promising for industrial deployment.

The researchers evaluated both methods holistically and in line with the US Food and Drug Administration’s requirements: that decontamination must safely and effectively inactivate the infectious agent without compromising the mask’s fit, liquid barrier resistance or filtering function. In their tests, the researchers exposed the masks to Mengovirus, a virus known for being notoriously hard to kill—even more so than SARS-CoV-2.

“Our study found that VHP decontamination methods showed good efficacy and were able to maintain the good fit of the masks with options for different system sizes,” Loh said, pointing out that VHP successfully reduced both viral and bacterial load on masks by at least 99.9 percent. Meanwhile, masks decontaminated with UV still showed substantial bacterial burden and some even had their wearability compromised.

The choice of which VHP machine to use boils down to practical considerations, added Loh. For instance, some machines can handle hundreds of masks at a time, making them ideal for large-scale use, while others can decontaminate only up to ten masks per batch, but do so much quicker. Nevertheless, deploying VHPs in hospitals or offices could be a step forward to tackle with the pressing problem of mask pollution.

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering (IMRE), Singapore Immunology Network (SIgN), Infectious Diseases Labs (ID Labs) and Institute of Bioengineering and Bioimaging (IBB).

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Wang, C.G., Li, Z., Liu, S., Ng, C.T., Marzuki, M. et al. N95 respirator decontamination: a study in reusability, Materials Today Advances 11:100148 (2021) | article

About the Researcher

Xian Jun Loh received his PhD in 2009 from the National University of Singapore and joined A*STAR in 2013. A polymer chemist with 20 years of experience working with biomaterials, Loh is currently Executive Director at the Institute of Materials Research and Engineering (IMRE). His research interests lie in the design of supramolecular and stimuli-responsive polymers and hydrogels for biomedical and personal care applications.

This article was made for A*STAR Research by Wildtype Media Group