WWI Chemical Weapons History
While chemical weapons were nothing new to
war, World War I was the first time that they figured prominently in battle
strategy. They were used by both sides,
to varying degrees.
The
[The] vapor settled to the ground like
a swamp mist and drifted toward the French trenches on a brisk wind. Its effect
on the French was a violent nausea and faintness, followed by an utter
collapse. It is believed that the Germans, who charged in behind the vapor, met no resistance at all, the French at their front
being virtually paralyzed.
The crippling effects of gas warfare on individual soldiers in WWI inspired unprecedented artistic expression of the harsher side of war, from poetry to painting. John Singer Sargent portrays the aftermath of a gas attack in his painting Gassed. Many lie dead from the gas attack, but even the survivors are terribly woundedbandages cover their eyes; mucous membranes were particularly vulnerable to poison gas.

Gassed by John Singer Sargent
Source: http://www.worldwar1.com/arm006.htm
Sources:
http://www.worldwar1.com/arm006.htm
http://my.webmd.com/content/article/61/67268.htm