Editing Chemical weapons in World War I (section)

==Delivery systems==
{{unreferenced section|date=January 2012}}
[[File:British gas attack at Montauban June 1916.jpg|thumb|right|upright|A British cylinder release at [[Montauban-de-Picardie|Montauban]] on the [[Somme (river)|Somme]], June 1916 – part of the preparation for the [[Battle of the Somme (1916)|Battle of the Somme]].]]

The first system employed for the mass delivery of gas involved releasing the [[gas cylinder]]s in a favourable wind such that it was carried over the enemy's trenches. The Hague Convention of 1899 prohibited the use of poison gasses delivered by projectiles. The main advantage of this method was that it was relatively simple and, in suitable atmospheric conditions, produced a concentrated cloud capable of overwhelming the gas mask defences. The disadvantages of cylinder releases were numerous. First and foremost, delivery was at the mercy of the wind. If the wind was fickle, as was the case at [[Battle of Loos|Loos]], the gas could backfire, causing friendly casualties. Gas clouds gave plenty of warning, allowing the enemy time to protect themselves, though many soldiers found the sight of a creeping gas cloud unnerving. Gas clouds had limited penetration, only capable of affecting the front-line trenches before dissipating.

Finally, the cylinders had to be emplaced at the very front of the trench system so that the gas was released directly over no man's land. This meant that the cylinders had to be manhandled through communication trenches, often clogged and sodden, and stored at the front where there was always the risk that cylinders would be prematurely breached during a bombardment. A leaking cylinder could issue a telltale wisp of gas that, if spotted, would be sure to attract shellfire.

[[File:Bundesarchiv Bild 183-F0313-0208-007, Gaskrieg (Luftbild).jpg|left|thumb|German gas attack on the eastern front.]]
A British chlorine cylinder, known as an "oojah", weighed {{convert|190|lb|kg}}, of which {{convert|60|lb|kg}} was chlorine gas, and required two men to carry. Phosgene gas was introduced later in a cylinder, known as a "mouse", that weighed {{convert|50|lb|kg}}.

Delivering gas via artillery shell overcame many of the risks of dealing with gas in cylinders. The Germans, for example, used {{convert|5.9|in|mm|adj=on}} artillery shells. Gas shells were independent of the wind and increased the effective range of gas, making anywhere within reach of the guns vulnerable. Gas shells could be delivered without warning, especially the clear, nearly odourless phosgene—there are numerous accounts of gas shells, landing with a "plop" rather than exploding, being initially dismissed as dud [[high explosive|HE]] or [[shrapnel shell]]s, giving the gas time to work before the soldiers were alerted and took precautions.

[[File:Livens gas projector loading.jpg|thumb|right|Loading a battery of [[Livens gas projector]]s]]

The main flaw associated with delivering gas via artillery was the difficulty of achieving a killing concentration. Each shell had a small gas payload and an area would have to be subjected to a saturation bombardment to produce a cloud to match cylinder delivery. Mustard gas did not need to form a concentrated cloud and hence artillery was the ideal vehicle for delivery of this battlefield pollutant.

The solution to achieving a lethal concentration without releasing from cylinders was the "gas projector", essentially a large-bore [[mortar (weapon)|mortar]] that fired the entire cylinder as a missile. The British [[Livens projector]] (invented by [[William Howard Livens|Captain W.H. Livens]] in 1917) was a simple device; an {{convert|8|in|mm|adj=on}} diameter tube sunk into the ground at an angle, a [[propellant]] was ignited by an electrical signal, firing the cylinder containing {{convert|30|or|40|lb|kg|abbr=on}} of gas up to 1,900 metres. By arranging a battery of these projectors and firing them simultaneously, a dense concentration of gas could be achieved. The Livens was first used at Arras on 4 April 1917. On 31 March 1918 the British conducted their largest ever "gas shoot", firing 3,728 cylinders at [[Lens, Pas-de-Calais|Lens]].