Men must always be on the look-out to help each other in case an anti-gas device is damaged by fire or accident. When a man is wounded, he must be watched to see that he does not remove his respirator or helmet until he is safely inside a protected shelter; if necessary, his hands should be tied.
Men must be warned that if they are slightly gassed before adjusting their respirators or helmets they must not remove them. The effect will wear off.
(2) Tactical Measures:
From the point of view of protection against gas, nothing is gained by men remaining in unprotected dug-outs or by moving to a flank or to the rear. It is, therefore, desirable that on tactical and disciplinary grounds all men in the front line of trenches should be forbidden to do these things. In support or reserve lines where there are protected dug-outs, it is advisable for men to stay in them unless the tactical situation makes it desirable for them to come out.
Nothing is gained by opening rapid rifle fire unless the enemy's infantry attacks. A slow rate of fire from rifles and occasional short bursts of fire from machine guns will lessen the chance of their jamming from the action of the gas and tends to occupy and steady the infantry.
It should be remembered that the enemy's infantry cannot attack while the gas discharge is in progress and is unlikely to do so for an appreciable time—at least 10 minutes—after it has ceased. It is, in fact, a common practice for the enemy infantry to retire to the second and third line of trench whilst gas is being discharged. There is, therefore, no object in opening an intense S.O.S. barrage of artillery on "No man's land" during the actual gas cloud and it is advisable that the warning to the artillery of a gas attack should be a signal differing from the ordinary S.O.S. signal, as the latter may have to be sent later if an infantry attack develops.
It must be remembered that smoke may be used by the enemy at the same time as, or alternately with, the gas and that under cover of a smoke cloud he may send out assaulting or raiding parties. A careful look-out must, therefore, be kept; hostile patrols or raiders may be frustrated by cross-fire of rifles and machine guns and should an assault develop the ordinary S.O.S. procedure should be carried out.
I. Precautions Against Gas Shells:
Owing to the small explosion which occurs with these shells, they are liable to be mistaken for blinds, and even when the gas is smelt men may not realize its possibly dangerous character at once and so may delay putting on respirators or helmets until too late. Men sleeping in dug-outs may be seriously affected unless they are roused. Men in the open air are unlikely to be seriously affected by poison gas shells, provided they put on respirators or helmets on first experiencing the gas. The following points should therefore be attended to:
(i.) All shells which explode with a small detonation or appear to be blind should be regarded with particular attention; the respirator or helmet should be put on at the first indication of gas and blanket protection of shelters adjusted.