Well, one of my additional duties was NBC NCO, but I didn't try to get my tanker's mask home. That would be ideal with the canister mounted in the center of your back and a connector for an outside air source. Especially since the M-17 was so clumsy.
The best ones I've found lately, other than the throwaways, are Israeli surplus. Tried the Russian model and they s<>k. The Israeli models are cheap, new filters are readily available, they have a lot better vision, and are a lot more comfortable.
But they still don't protect you against fumes. Best bet for that is over-pressure, just like in a tank.
