Editing Chemical weapons in World War I (section)

==Countermeasures==
None of the First World War's combatants were prepared for the introduction of poison gas as a weapon. Once gas was introduced, development of gas protection began and the process continued for much of the war, producing a series of increasingly effective gas masks.<ref name="Gross" />

Even at Second Ypres, Germany, still unsure of the weapon's effectiveness, only issued breathing masks to the engineers handling the gas. At Ypres a Canadian medical officer, who was also a chemist, quickly identified the gas as chlorine and recommended that the troops urinate on a cloth and hold it over their mouth and nose. Urine would be left to sit for a period so that the ammonia would activate; this would neutralize some of the chemicals in the chlorine gas, which allowed them to delay the German advance at Ypres, giving the allies time to reinforce the area when French and other colonial troops had retreated.<ref>{{cite web | url=https://thisiscanadiana.com/blogposts/2018/11/8/canadians-amp-the-poison-gas-of-flanders | title=Canadians & the Poison Gas of Flanders | date=8 November 2018 }}</ref> The first official equipment issued was similarly crude: a pad of material, usually impregnated with a chemical, tied over the lower face. To protect the eyes from tear gas, soldiers were issued gas goggles.

The next advance was the introduction of the gas helmet, which was basically a bag placed over the head. The fabric of the bag was impregnated with a chemical to neutralize the gas; the chemical would wash out into the soldier's eyes whenever it rained. Eye-pieces, which were prone to fog up, were initially made from [[talc]]. When going into combat, gas helmets were typically worn rolled up on top of the head, to be pulled down and secured about the neck when the gas alarm was given. The first British version was the [[hypo helmet]], the fabric of which was soaked in [[Sodium thiosulfate|sodium hyposulfite]] (commonly known as "hypo"). The British P gas helmet, partially effective against phosgene and with which all infantry were equipped with at [[Battle of Loos|Loos]], was impregnated with [[Sodium phenoxide|sodium phenolate]]. A mouthpiece was added through which the wearer would breathe out to prevent [[carbon dioxide]] build-up. The [[adjutant]] of the 1/23rd Battalion, [[London Regiment (1908–1938)|The London Regiment]], recalled his experience of the P helmet at Loos:

{{Blockquote|The goggles rapidly dimmed over, and the air came through in such suffocatingly small quantities as to demand a continuous exercise of will-power on the part of the wearers.<ref>{{Cite book
 | author=Warner, Philip
 | year=2000
 | title=The Battle of Loos
 | publisher=Wordsworth Editions
 | page=103 | isbn=1-84022-229-8 }}</ref>}}

A modified version of the P helmet, called the PH helmet, was issued in January 1916, and was impregnated with [[hexamethylenetetramine]] to improve protection against phosgene.<ref name="cbwinfo" />

Self-contained box respirators represented the culmination of gas mask development during the First World War. Box respirators used a two-piece design; a mouthpiece connected via a hose to a box [[filter (air)|filter]]. The box filter contained granules of chemicals that neutralised the gas, delivering clean air to the wearer. Separating the filter from the mask enabled a bulky but efficient filter to be supplied. Nevertheless, the first version, known as the [[large box respirator]] (LBR) or "Harrison's Tower", was deemed too bulky—the box canister needed to be carried on the back. The LBR had no mask, just a mouthpiece and nose clip; separate gas goggles had to be worn. It continued to be issued to the artillery gun crews but the infantry were supplied with the "[[small box respirator]]" (SBR).

The Small Box Respirator featured a single-piece, close-fitting rubberized mask with eye-pieces. The box filter was compact and could be worn around the neck. The SBR could be readily upgraded as more effective filter technology was developed. The British-designed SBR was also adopted for use by the [[American Expeditionary Force]]. The SBR was the prized possession of the ordinary infantryman; when the British were forced to retreat during the [[German spring offensive]] of 1918, it was found that while some troops had discarded their rifles, hardly any had left behind their respirators.

Horses and mules were important methods of transport that could be endangered if they came into close contact with gas. This was not so much of a problem until it became common to launch gas great distances. This caused researchers to develop masks that could be used on animals such as dogs, horses, mules, and even carrier pigeons.<ref name="Fitzgerald2008">{{cite journal |last=Fitzgerald |first=Gerard |title=Chemical Warfare and Medical Response During World War I |journal=American Journal of Public Health |date=April 2008 |volume=98 |issue=4 |pages=611–625 |doi=10.2105/AJPH.2007.11930 |pmid=18356568 |pmc=2376985}}</ref>

For mustard gas, which could cause severe damage by simply making contact with skin, no effective countermeasure was found during the war. The kilt-wearing Scottish regiments were especially vulnerable to mustard gas injuries due to their bare legs. At [[Nieuwpoort, Belgium|Nieuwpoort]] in [[Flanders]] some Scottish battalions took to wearing women's tights beneath the kilt as a form of protection.

Gas alert procedure became a routine for the front-line soldier. To warn of a gas attack, a bell would be rung, often made from a spent artillery shell. At the noisy [[artillery battery|batteries]] of the siege guns, a compressed air strombus horn was used, which could be heard {{convert|9|mi|km|spell=in}} away. Notices would be posted on all approaches to an affected area, warning people to take precautions.

Other British attempts at countermeasures were not so effective. An early plan was to use 100,000 fans to disperse the gas. Burning coal or [[Silicon carbide|carborundum]] dust was tried. A proposal was made to equip front-line sentries with diving helmets, air being pumped to them through a {{convert|100|ft|m|abbr=on}} hose.

The effectiveness of all countermeasures is apparent. In 1915, when poison gas was relatively new, less than 3% of British gas casualties died. In 1916, the proportion of fatalities jumped to 17%. By 1918, the figure was back below 3%, though the total number of British gas casualties was now nine times the 1915 levels.

<gallery widths="200px" heights="200px">
File:Smelling Case of War Gases, Clifton Park Museum.jpg|A smelling case to allow officers to identify the gas by smell and thus act appropriately for protection and treatment
File:Various gas masks WWI.jpg|Various gas masks employed on the Western Front during the war
File:Vickers machine gun crew with gas masks.jpg|British [[Vickers machine gun]] crew wearing PH gas helmets with exhaust tubes
File:Australian infantry small box respirators Ypres 1917.jpg|Australian infantry wearing small box respirators, [[Ypres]], September 1917
File:Gas alert Arthur Streeton.jpg|''Gas Alert'' by [[Arthur Streeton]], 1918
</gallery>