I don't grasp the bizarre process of percarbonate in water but masks outside the water. My spontaneous thoughts (but I'm very bad on biology) would be:
- Sterilize in an authentic autoclave. Maybe a cooking autoclave, with water - but only if no exiting vapour carries viruses.
- Wash in a washing machine, with washing powder, preferably hot if the masks survive that.
- Immerse the masks in the percarbonated water.
Percarbonate in water releases hydrogen peroxide. This isn't still oxygen in water: the peroxide must decompose first, and this reaction is hard to predict. So, no way to predict an oxygen concentration above the solution, but the probable outcome is: normal air. And I'm not sure at all that O2
destroys viruses. Peroxide is much more active.
If you achieved oxygen around the masks, for which an oxygen bottle is much simpler and predictable, it would be a BIG explosion risk, possibly with detonation. Organic fabrics burn well, in an enclosure: boom.