[Jimbee (OP)]

When I was in HS chemistry class, our teacher once told us a story. He fought in WWII and he often told us war stories. He said one time he and his fellow soldiers were in a battle. And their sergeant turned them and said, listen this is a gas attack. We don't have time to go back and get our gas masks. So urinate in to your hankies, cover your faces and run fast. Also, when I was still in HS, the Dow Chemical Bhopal gas tragedy occurred. I still remember, the government in India told people there, if your are still in an area with poisonous gas, saturate a large bath towel with water. Then lay on the floor and cover your whole head with it until it is safe.

Why is a cloth saturated with water considered a good filter and impromptu gas mask against some pretty dangerous airborne chemicals sometimes? Just water is involved, not even charcoal. Chemically, how would a gas mask like that even work?

[alancalverd]

I'm surprised that soldiers advanced without taking all their PPE with them.

Aviators have a saying:

"These things will not save your life: the sky above you, the runway behind you, the fuel you left in the truck, and anything that happened yesterday."

[vhfpmr]

It intrigues me that something as seemingly mundane as 'activated charcoal' appears to be a universal barrier against all poisons. I would have expected a fresh race to find a new high-tech protection against each new poison.

Aviators have a saying:

"These things will not save your life: the sky above you, the runway behind you, the fuel you left in the truck, and anything that happened yesterday."

"It's better to be down here wishing you were up there, than up there wishing you were down here." (Good for fellwalking, too)
"There are old pilots, and there are bold pilots, but there are very few old bold pilots."

[alancalverd]

Charcoal, and to some extent water, are just very good at absorbing large or reactive molecules, with the remarkable and happy exception of cold oxygen. Problem with "protection against each new poison"  is guessing what a sophisticated scumbag like Putin is going to throw at you next (though Porton does try to keep up with fashionable nerve agents) , and in the case of an unsophisticated mass murderer like Assad, swimming-pool chorine is a reasonable guess anyway.

[paul cotter]

With regard to Jimbee's original question regarding wet cloth the answer is simple. Many toxic substances such as methyl isocyanate(Bhopal) or phosgene(ww1) are hydrolytically unstable and passage through sufficient water will effectively neutralise them- what constitutes sufficient water depends on kinetics of the hydrolysis. As far as I know no gas was used in ww2.   

[vhfpmr]

As far as I know no gas was used in ww2.

That's what I thought too, but Google is telling me phosgene (apart from Zyklon B, of course).