Hey folks,
I'm sure all of you have heard a lot of this, but I'm going to restate it anyhow, just so you can hear it firsthand from another AR-15.com-er.
The only person a gas mask sale benefits is the gasmask salesman. (Unless you're a militaria collector, then, be my guest) Military gas masks are your worse bet. First off, if you have any more than 24 hours of facial hair growth in the sealing area, your fit factor is probably nil. I am an industrial hygienist for a living and I fit-test people for respirators every day. I've never seen a passing test when someone had more than one day's growth. In fact, OSHA will cite a company if employees are wearing respirators with any facial hair in the sealing area.
Second, if you haven't had a quantitative fit-test on the piece of respiratory equipment you intend to use, chances are that it probably doesn't fit you properly.
Lastly, your first warning that you are under a Sarin or Tabun gas attack would be the guy next to you keeling over. (or maybe you'd be his first warning) in any case, a drop on your skin is more than enough to do the trick, so don't waste your money on gas masks or "biochem suits." Modern biological and chemical warfare agents are lethal in concentrations that are undetectable by the normal 5 senses. Sorry about your luck.
My advice, prepare for more likely emergencies:
I have become affiliated with a company called World Prep (www.worldprep.com). Worldprep manufactures preparedness kits that are amazingly well thought out (Designed by a Watercraft Officer, a Navy Seal and an Environmental Engineer) They sell several different sizes and types of kits for less than you can assemble the components for yourself.
These kits use premium emergency and preparedness products in custom-designed bags that are of a very high quality.
OFFICE PREPAREDNESS: The newest kit they have is for people who work in large buildings or in big cities. It's a small bag that attaches to a desk or wall and hardly takes up any space. Inside it has 2 4oz packs of emergency drinking water, a NIOSH-approved N100 paper respirator (the company I work for uses these for protecting workers against lead dust and other hazardous materials - they fit everyone I've ever tested on them so far) A 2AA aluminum flashlight (like a mag-lite) a super loud whistle, a lightstick and a mylar emergency blanket.
I highly recommend you check this stuff out, as their doesn't appear to be any end of disastrous events happening in population centers, even if we do turn afghanistan into a smoking hole.