I put an N95 mask into my toaster oven at 200°F/93°C. I learned that many parts of the mask are not cloth, but plastic. Those parts melted within a couple of minutes, leaving the mask unusable.
That formula is very ballpark! It’s actually 9/5C+32=F, and (F-32)*5/9=C. Yes, much harder to remember, but the 56°C example above using your formula gives 142°F, when the actual answer is 132.8℉.
I was wondering the same thing myself: If a thorough washing of hands before and after opening the package would suffice?