I read on https://www.20minutes.fr/sante/2749451-20200328-coronavirus-traiter-masques-ffp2-reutiliser-possibilites-actuelles-limitees (mirror):

Plusieurs procédés ont déjà fait l’objet de tests, rappelle-t-il : « Les ultraviolets ont montré une efficacité. La difficulté de l’UV, c’est qu’il faut arriver à le diffuser partout. Certaines études ont montré que, selon la forme du masque, les UV vont à certains endroits, mais ils ne vont pas à d’autres.

Google Translate:

Several processes have already been tested, he recalls: "Ultraviolet rays have shown their effectiveness. The difficulty with UV is that you have to be able to distribute it everywhere. Some studies have shown that, depending on the shape of the mask, UV rays go to certain places, but they don't go to other places.

Which studies have shown that UV radiations fail to reach some part on the mask and therefore may not be suitable for sanitizing masks?

I have crossposted the question at:

  • 3
    +1 but it might be a more suitable question for Skeptics SE. Commented Mar 28, 2020 at 13:43
  • 1
    It is also known that viruses like these only have a short lifespan without a living host. So it is interesting to know how the virus loses its potency after being exposed to UV radiation over time. Although maybe they just don't recommend it or even risk to tell people about it due to different levels of UV per area, time of day, and etc.
    – Pherdindy
    Commented Apr 1, 2020 at 3:10

1 Answer 1


This may not be the exact issue alluded to in your source, as it’s not caused by the shape of the mask directly, but Fisher, Williams, & Shaffer (2010) finds that the effectiveness of UV germicidal irradiation is limited by the accumulation of soil (skin residue) on N95 FFR masks, which decreases the penetration of UVGI. See: https://www.cdc.gov/niosh/nioshtic-2/20037276.html

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