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 O
2 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.