UPDATE!
I had a bit of a brainstorming moment a few minutes ago thinking about better ways to do this as possibly an add-on pack...and I thought of some good ideas!
Basically what came across my mind was how stupid it would be to just enable a gasmask and boom you are free to breathe, while not having it on you are instantly doomed until you put one on... And that is what brings me to the idea. I said above that I would like to see safe "zones" (hopefully acts like a zonebrick in all aspects but adds a breathable atmosphere within the zonebricks), and that still stands. And at the same time I would like the gasmask to help against chemical grenades (like the one already made) HOWEVER you need to pick up filters or be able to purchase them (I have a bunch of add-ons so it's possible with VCE and the TotalRPG mod on my server no problem) and it will give you a designated time when you have the mask on for how long your filters last. Also if you don't have one on, the timer pauses? If you have the BLCurrency mod or know how it works, I'll use that as an example. When you pick up money it disappears and doesn't respawn, it clears the item in other words once received. so all-in-all what I am REALLY wanting done here, is a mask, consumable item, ui thing for the countdown on air-time, and a zonebrick that allows for breathing without the mask.