Disinfecting and re-using medical masks and N95 respirator masks

Personal protective equipment, including face masks, are an essential piece of equipment for healthcare workers, since the spread of respiratory viruses, such as the novel coronavirus (SARS-CoV-2), occurs primarily via droplets that are dispersed by infected individuals through coughing and sneezing. However, due to the current pandemic and subsequent surge in use of personal protective equipment, there has been a significant shortage of masks, making it difficult for healthcare workers to remain protected.

In an effort to conserve current supplies, many healthcare workers re-use masks that are typically on single-use items. In addition, many have resorted to attempting to decontaminate their masks in an effort to further extend their use.

Can masks be disinfected and re-used?

In an effort to conserve masks, healthcare workers are currently extending the use of masks to more than one patient encounter even though these are ‘single-use’ items.^1,2 This practice may significantly increase risk of infection due to the continuous touching of the mask, which may become contaminated after extended use. Repeated use increases the chances that the surfaces of the mask could be contaminated with virus particles, which can cause infection if the wearer touches these surfaces and then touches their face.

The possibility of decontaminating and reusing masks as a method of prolonging their use has recently been explored. Systematic scientific research will be necessary to clearly define the best possible methods that have sufficiently decontaminate, while maintaining the integrity of the masks to ensure they remain effective.

Decontamination using steam and heat

A recent study reported that wrapping N95 masks in protective peel pouches and then steam sterilizing them may be a successful method of decontamination.³ Another study tested a relatively simple method of sterilizing masks, where medical masks and N95 respirator masks were placed in plastic bags and steamed on a pot of boiling water for five minutes. In this way, the masks remained dry, ensuring they remained effective, while the researchers found a complete inactivation of avian coronaviruses that were used to simulate contamination.⁴ Similarly, researchers investigated whether a rice cooker could be used to steam-sterilize masks, comparing this with dry-heat decontamination.⁵ The steam treatment took a maximum of 15 minutes, which included five minutes of active steaming. Dry heat contamination was performed in an oven, which consisted of exposing the masks to 100-degree heat for 15 minutes. The researchers found the steam treatment to be a superior method of decontaminating the masks compared to the dry heat; they also reported that the steaming method was more effective than UV light decontamination. This study did not, however, assess the effectiveness of the masks following decontamination.

Disinfection using UV irradiation has previously been used for drinking water and air. A recent study reported that using a UV-C disinfection cabinet was effective at decontaminating N95 masks when using a 31-minute decontamination cycle.⁶

In another study using a UV-C germicidal lamp, researchers found that this method was able to achieve decontamination of masks contaminated with SARS-CoV-2. The researchers reported that the decontamination of masks took a longer amount of time compared with hard surfaces, and may also be dependent on how contaminated the masks are to begin with.⁷

References:

1. Strategies for Optimizing the Supply of N95 Respirators: Crisis/Alternate Strategies. Center for Disease Control website https://www.cdc.gov/coronavirus/2019- ncov/hcp/respirators-strategy/crisis-alternate-strategies.html
2. Centers for Disease Control and Prevention. Cloth masks and mask sterilisation as options in case of shortage of surgical masks and respirators. Available at: https://www.ecdc.europa.eu/sites/default/files/documents/Cloth-face-masks-incase-shortage-surgical-masks-respirators2020-03-26.pdf.
3. Carrillo, I., Floyd, A., Valverde, C., Tingle, T., & Zabaneh, F. (2020). Immediate Use Steam Sterilization (IUSS) Sterilizes N95 Masks Without Mask Damage. Infection Control & Hospital Epidemiology, 1-5. doi:10.1017/ice.2020.145  
4. Ma, Q.‐X., Shan, H., Zhang, C.‐M., Zhang, H.‐L., Li, G.‐M., Yang, R.‐M. and Chen, J.‐M. (2020), Decontamination of face masks with steam for mask reuse in fighting the pandemic COVID‐19: experimental supports. J Med Virol. Accepted Author Manuscript. doi:10.1002/jmv.25921
5. Li, DF., Cadnum, JL., Redmond., SN, Jones, LD., Donskey, CJ. (2020). It’s Not the Heat, It’s the Humidity: Effectiveness of a Rice Cooker-Steamer for Decontamination of Cloth and Surgical Face Masks and N95 Respirators, AJIC: American Journal of Infection Control. doi: https://doi.org/10.1016/j.ajic.2020.04.012
6. Cadnum JL, Li DF, Redmond SN, John AR, Pearlmutter B, Donskey CJ. Effectiveness of Ultraviolet-C Light and a High-Level Disinfection Cabinet for Decontamination of N95 Respirators. Pathog Immun. 2020;5(1):52‐67. Published 2020 Apr 20. doi:10.20411/pai.v5i1.372
7. Fischer, R, Morris, DH, van Doremalen, N, Sarchette, S, Matson, J, Bushmaker, T, Yinda, CK, Seifert, S, Gamble, A, Williamson, B, Judson, S, de Wit, E, Lloyd-Smith, J, Munster, V. Assessment of N95 respirator decontamination and re-use for SARS-CoV-2. medRxiv 2020.04.11.20062018; doi: https://doi.org/10.1101/2020.04.11.20062018

Image by Engin Akyurt from Pixabay