Half-mask protection devices are interesting replacement options allowing the protection of workers during the COVID-19 pandemic. When used properly, these masks offer a superior protection to workers when compared with disposable filtering face masks. They also offer a solution to a potential shortage of disposable masks. An independent study report has shown that routine use of masks in health care environments is a viable option.


One key to safely using reusable masks as breathing protection against the coronavirus SARS-CoV-2 is a good maintenance, cleaning and storage program for the masks 
[1]. 

You will find below two procedures: one simplified procedure for non-medical environments presenting less risks and the other for medical environments (You can adapt these procedures to your specific situation). The procedure for medical environments takes into account the risks posed by the coronavirus SARS-CoV-2 and is inspired from methods presented by Lawrence et al. (2017)[2], Bessesen et al. (2015)[3], the CDC's Guideline for Disinfection and Sterilization in Healthcare Facilities[4] and technical notes from company 3M in relation with cleaning and disinfecting masks following potential exposure to Coronaviruses[5][6].

I - Simplified cleaning procedure in non-medical environments

  1. Remove the P3 filter case and set aside on disposable absorbent paper or tissue.
  2. Clean the mask with warm water not exceeding 43°C (109°F) and brush with a soft brush until clean. If necessary, add neutral detergent. 
    Do not use cleaning products containing lanolin or other oil and do not use a metallic brush.
  3. Rinse parts with flowing warm water. It is important to rinse well. Soap and disinfecting products left drying on the mask can irritate the skin and cause dermatitis. They may also damage rubber components.
  4. Dry with a soft clean cloth or an absorbent paper or let dry.
  5. Disinfect with a disposable absorbent paper, wipe or tissue and a hydroalcoholic solution (especially the silicon part in contact with the face).
  6. Wait 5 minutes before wearing.
  7. For the filter case: disinfect the filter case using a disposable absorbent paper or wipe and a hydroalcoholic solution and brush gently. Wait 5 minutes before wearing.
    Warning: exposure of filtering media inside the case to liquids could impede filtration efficacy.
  8. Dispose of paper, wipe or tissue...
  9. Wash your hands.

If you must remove your mask several times during your duty, we recommend the following:

  1. Wash your hands or use hydroalcoholic gel before touching your mask.
  2. Clean the silicon part in contact with your face with disinfecting absorbent paper, wipe or tissue and hydroalcoholic gel.
  3. Replace and fix your mask.
  4. Using the same paper, wipe or tissue with hydroalcoholic gel, wipe gently your mask and the case, then dispose of the paper, wipe or tissue.
  5. Wash your hands or use hydroalcoholic gel.

Choice of disinfectant: Hydralcoholic gel or commercial disinfecting wipes can make the mask unusable because of a strong residual smell. Too many fragrances penetrate the mask. Select carefully your disinfectant and test if beforehand.

II - Cleaning procedure in a medical environment exposed to coronavirus SARS-CoV-2

A) Cleaning procedure proposal for cleaning breathing apparatus used with COVID-19

  1. Remove the P3 filter case and set aside on disposable absorbent paper or tissue.
  2. Clean the mask with warm water not exceeding 43°C (109°F) and brush with a soft brush for at least one minute. 
    Do not use cleaning products containing lanolin or other oil and do not use a metallic brush.
  3. Disinfect the mask by immersing it for one minute in Sodium hypochlorite solution (5000 ppm, see below). Immerse face down to avoid the formation of air bubbles in the mask. Rotate to free residual air bubbles.

    Hypochlorite solution (5000 ppm chlorine) can be made by adding 100 ml of bleach (5%) in 900 ml of warm water. Commercial and industrial products have varying bleach content. It is recommended to use this chlorine dilution calculator to validate the volumes needed to make the solution.
    Note: 1% is equivalent to 10 000 ppm

  4. Rinse the mask thoroughly with flowing warm water for at least 2 minutes. Remove excess water. It is important to rinse well. Soap and disinfecting products left drying on the mask can irritate the skin and cause dermatitis. They may also damage rubber components.
  5. The mask must be dried with a clean cloth, absorbent paper or let dry in a clean place.
  6. Store your mask in a clean non-hermetic container to avoid humidity. 
  7. Check air-proofing at every use.

    Note: Bleach can cause a premature use of elastic straps. However, it is not recommended to remove them so as to wear the mask faster in times of pandemic.

B) Cleaning procedure proposal for particulate filter case of reusable elastomer masks.

Consider the following for the selection and maintenance of particulate filters

  • Encapsulated particulate filters in rigid shells (cases) are highly recommended if you plan to reuse the filters. The shell is easier to clean because of its smooth surfaces. Although reuse is not normally recommended for infectious agents, this solution is proposed in times of pandemic and to avoid shortages.
  • It is unlikely that filters get clogged in healthcare environments. The frequency of replacement of filters must be decided based on infection prevention considerations. The mask is used to filter air. Contaminants will thus collect on the filter. The final user takes responsibility for the reuse of the filter against SARS CoV-2.

Procedure:

  1. Take the particulate filter (case) left on a humid wipe while cleaning the half-mask.
  2. Gently brush the external surfaces of the case with a cloth or wipe and disinfectant (see NOTE below). Choose a disinfectant that is listed as effective against the SARS-CoV-2 virus as recommended by the EPA. Ensure that contact times are followed (For example, one minute minimum for the sodium hypochlorite solution at 5,000 ppm chlorine. The surface to disinfect must therefore stay in contact, or be brushed, for one minute).
  3. Rinse by brushing gently with a clean cloth and water.
  4. Warning: exposure of filtering media inside the case to liquids could impede filtration efficacy.
  5. Dry with a dry cloth or let dry in a clean space.
  6. Always keep the case in a non-hermetic container (new, clean and well maintained) separated from the mask.
  7. Always check for air-proofing.



[1] Lara, J. and Vennes, M. Guide pratique de protection respiratoire Canadien, 2e édition. Commission de la santé et sécurité du travail et Institut de recherche Robert-Sauvé en santé et en sécurité du travail. 

[2] Lawrence, C., Harnish, D. A., Sandoval-Powers, M., Mills, D., Bergman, M. and Heimbuch, B. K. (2017). Assessment of half-mask elastomeric respirator and powered air-purifying respirator reprocessing for an influenza pandemic. American journal of infection control, 45(12), 1324-1330.

[3] Bessesen, M. T., Adams, J. C., Radonovich, L. and Anderson, J. (2015). Disinfection of reusable elastomeric respirators by health care workers: a feasibility study and development of standard operating procedures. American journal of infection control, 43(6), 629-634.

[4] Rutala, W.A., Weber, D.J. and the Healthcare Infection Control Practices Advisory Committee. (2008). Guideline for Disinfection and Sterilization in Healthcare Facilities; updated 2009. https://www.cdc.gov/infectioncontrol/pdf/guidelines/disinfection-guidelines-H.pdf

[5] 3M. (2020). Personal Safety Division Cleaning and Disinfecting 3M Reusable Elastomeric Half and Full Facepiece Respirators following Potential Exposure to Coronaviruses. https://multimedia.3m.com/mws/media/1793959O/cleaning-and-disinfecting-3m-reusable-respirators-following-potential-exposure-to-coronaviruses.pdf

[6] 3M. (2020). Cleaning and Disinfecting 3M Powered Air Purifying Respirators. https://multimedia.3m.com/mws/media/1793956O/cleaning-and-disinfecting-3m-paprs-following-potential-exposure-to-coronaviruses.pdf