Letter to the editor: Mask Decontamination – a review of the literature

Letter to the Editor from: Dr. Brian Kirk, Brian Kirk Sterilization Consultancy Group Ltd, 10 Harcourt Place, Castle Donington, Derby DE74 2XJ, U.K., on: I. Jullian-Desayes, L. Degruel, G. Rabatel, C. Lambert: Mask Decontamination – a review of the literature. Central Service 2021; 29(3):173–179. Read the main article here. | Login for epaper subscribers


The publication by Jullian-Desayes et al [1] is most interesting and welcome. Whilst highlighting the decontamination processes which can be used (I am loathe to call them sterilization processes because many appear not to be validated processes [2]), the paper highlights some of the additional considerations which must be made other than the choice of decontamination process itself. Within the Institute of Healthcare Engineering and Estates Management (IHEEM) the decontamination technical platform produced a guidance note [3] which considered some of the additional points which needed to be considered when discussing decontamination of single use respirator masks. The following list considers these and may inform further discussion.

  1. In the UK the competent authority, MHRA, stated that respirator masks should not be reprocessed and were not covered by any medical device regulation. They are classed as personal protective equipment covered by health and safety legislation and the directives framing national regulation should be consulted.

  2. Sterile reprocessing departments operate a decontamination cycle in which contaminated devices are introduced at the start and end clean, sterile and ready to use. Intermediate steps include manual cleaning to remove gross contamination, automated cleaning and disinfection, inspection and packaging and then sterilization in a validated process. During each step the environment and PPE used by operators has different functions. Dirty instruments are regarded as an infection risk and so operators are protected against contamination from the instrument using appropriate PPE. In the packaging and inspection room the devices are clean and disinfected having a very low bioburden. Operators wear attire designed to prevent them contaminating the instruments. Since the majority of decontamination processes discussed in the paper involved use of a sterilizer, one must assume that any single use PPE would be introduced into the inspection and packaging area so that inspection could take place to make sure the respirators remained intact before being packaged and placed in the sterilizer. Returned PPE has the potential to be highly contaminated with pathogenic microorganisms and it would be very undesirable to introduce them into the sterilization area or packaging area which is a clean, controlled environment, where disinfected devices are inspected and packaged.

  3. Material Compatibility. Materials used to manufacture respirator masks must retain their properties and not be altered by the decontamination process. Many decontamination processes described use corrosive and toxic agents in order to kill microorganisms. Others use high temperatures all of which can change material properties.

  4. Respirator fit. All respirators must fit correctly in order to be effective. If the decontamination process deforms the respirator then close fit may be lost resulting in leakage of infectious aerosols into the mask.

  5. Filtration efficiency. Respirator masks not only rely on physical filtration to exclude particles but also on surface properties such as electrostatic charges to retain particles. If these properties are lost due to the decontamination process, filtration efficacy is damaged.

  6. Physical damage. It is possible that in removing respirator masks, users can damage the material without realising. This means some form of inspection is needed to ensure integrity of the mask before decontamination. This results in operators needing to handle highly infectious devices.

  7. Process residuals. Some decontamination processes use microbicidal chemicals for their action. Residuals can remain which are toxic to humans. Clearly it is highly undesirable to have users placing a respirator mask containing process residuals over their airways.

  8. Viral inactivation. Many decontamination agents are highly effective at killing bacteria and viruses. However the introduction of bio-contamination in the form of spittle, sputum and inorganic salts from sweat can dramatically reduce process efficacy. This is why devices are cleaned before they are sterilized.

  9. Personal hygiene. Since respirator masks cannot be cleaned it would be essential to ensure a reprocessed mask is returned to its original user creating logistical complexity.

The emergence of the Covid-19 pandemic placed enormous strain on the supply chain of PPE leading to shortages. This lead to many authorities around the world seeking ways of decontaminating used single use PPE including respirator masks. In the rush to ensure front line health care workers were adequately supplied with PPE many suggestions for decontamination of PPE were published. However it is also essential to consider all factors before embarking on a process which allows continuity of supply. It goes without saying that everyone appreciates the work of front line workers in the current health crisis. However, as is often the case, solving one problem, i.e. PPE shortages, can lead to creating many others. Careful comprehensive consideration and risk assessments taking into account all factors should be carried out before embarking on a PPE decontamination approach. Hopefully as the pandemic subsides the PPE supply chain will catch up and the need to decontaminate single use respirator masks will diminish and disappear.



1 Jullian-Desayes, I et al, Mask Decontamination – a review of the literature. Zentr Steril 2021; 29(3):173–179.

2 Definition of sterilization in ISO 11139:2018, Sterilization of health care products, Vocabulary – Terms used in sterilization and related equipment and process standards, International Standards Organisation, Geneva, Switzerland

3 The Institute of Healthcare Engineering and Estate Management (IHEEM), “Reprocessing of Personal Protective Equipment (PPE) – An IHEEM Factsheet (1 – Version 1), Apr 2020, www.iheem.org.uk.


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