All of the above. WWI combatants used cotton pads dipped into a solution, protective mask and urine drenched cloth to safeguard from chemical warfare.The first major poison gas attack in WW1 took place on 22nd April 1915, when the Germans released 150 tons of chlorine gas near Ypres.
Explanation:
Chlorine gas attack by the German soldiers resulted in the death of thousand french soldiers. Men who had the knowledge of chemistry acknowledged it to be the chlorine gas from its unique smell and they knew the simple solutions which counter effected the poisonous gas. They dipped the cloth in the simple solutions that were available in the trenches and that seemed to neutralize the gas effect.
But it did not prove to be efficacious as the chlorine gas was released in a concentrated manner which proved to be fatal for the french soldiers. Chemicals like sodium bicarbonate and sodium hyposulphate which were used in photography were also used but there was no lasting effect. Finally, The Canadian flank came up with a remarkable observation stating that urine soaked cloth masks were effective in combating the concentrated chlorine gas.
