There are a few variables when dealing with tavor gas face. The biggest is probably the type of suppressor you're running and the next is the ammo you are feeding it. I know with mine (I run a socom 556 mini and standard and a 762rc) the IWI ammo that I used to buy in bulk was way dirtier than anything else I've fed it. I never noticed it until I put a can on it then the whole gun got nasty. Also you can try and seal it with silicon if you want, I didn't but I've heard of those that have.