That said, if you don't have any other mask, I fail to see how viral material can survive a soak in alcohol for a few minutes and then drying overnight in a warm spot away from flames (alcohol is flammable).
"Disposable N95 Masks Can Be Decontaminated, Researchers Confirm":
The linked NYT article points out "Of those methods, they did not recommend ethyl alcohol because although it killed the virus, it degraded the mask material."
The Times article may represent a scientific example of Johnson's exemplar.
Note that TCID and some other specialty treatment centers (TCID solely treats TB I believe) have been doing this for a while (although not necessarily with 3M masks).
Results published earlier this month showed no detectable virus on wood after two days, and additionally found non-flat surfaces, like wood, to be more resistant. It seems unlikely that the virus will last 4 days on outdoor decking as WebMD claims.
* COVID19 isn't the only threat. Other germs can multiply with time. This is not the time to go to a hospital with an infection.
* When I last looked, there was preliminary evidence COVID itself survives surprisingly long in a mask (I think days)
It's annoying to see them going to people who don't use them right (a Republican senator was wearing one upside down). Incorrectly used, they're no better than a surgical mask.