Save you some time Cali..ask and you shall receive!
The TO goes over these things, but focus on a few things, if the harness looks warn, replace it. Inspect the rubber face piece for a dry or brittle cracks..if it does, return it immediately to the person you bought it from. Inspect the nose piece, make sure that the drinking tube is not cut or chewed on. When you pull off the old filter, inspect the inner inlet cover..they will look like old M17 inlet, but makes sure it is seeded correctly (laying flat). Inspect the thread where the cartridge is located, screw the old filter back on and make sure it seeds well and that is not at an angle, if it does, then the thread to the mask inlet, are worn and that means either replacing it which is not difficult, but costly...save you some time, send it back.
Me, I never buy from those Army Supply places, I know their cheap, but for me, with the line of work I've done, better to get one that is new and from a reputable source. Used ones will be okay against CS agents, but who wants to chance it for a Nuc, bio or chem threat. My take, some have different views on the subject.
Personally, you want to go cheap, wear a paper gown, some surgical gloves and a defective mask...go for it. My theory than is why did you spend all that money on some high tech piece of firearm, only to be laying on to the wayside, choking on your own blood.
Hope the T.O. helps you out.
