[YoungKentuckyConservative]

I've done a little bit of research, nothing too serious, but I've concluded the following:

1. Buy new, by American, if possible. You can't trust a used mask. It's a simple setup, but why take the risk when your life depends on it.

2. The most important feature is that canister you are questioning. It MUST be able to protec you against the appropriate agents, in my case all known NBC, and it MUST be in reasonable condition. You can identify the age of most cannisters by the serial/production number. If it's a 3M cannister you'll find many websites that help you identify the production age.

Also, make sure you have the Tyvek suits to go along with it, or you might be surviving long enough to watch your skin melt.

[King_of_Hindsight]

One issue with the M14 is the cannister is obviously OEM, but un,marked. I know from my days in the corps, late 70's, early 80's, we used the M17A1, with unmarked filters.