<u>E</u>very tried to do heavy work for more than an hour in old soviet mask? It’s rough as you over heat and start drowning in your own sweat.
If you are that worried about full environmental contamination better off practicing l with moon suit and a papr supplied air system, it is very impractical for anything but end of the world stuff. I have had many hours in one, work goes to crawl, you are more worried about a su it puncture than anything else, and no one has proper decontamination set up to extract someone from that in regular world. You can’t put it on fully by yourself and you pray they didn’t cheap out on duct tape yeah duct tape holds part of the suit together.
Easy way to see if you can use cbrn mask and difference is to play paintball in them as your face shield. There is a you tube video of how to make a mask mask from 2 L soda bottle would I trust my left to it no unless that or nothing because well then nothing left to lose.
Would tape a real filter or screw one into the threaded pour spout not just a dust mask