(v) Should an infantry attack develop, the normal procedure of S. O. S. will be carried out.
(vi) Troops in the front line not affected by gas must be warned to be prepared to bring a cross fire to bear on the enemy when he attempts to advance against a gassed portion of the trench.
(vii) If a relief is in progress, units should stand steady as far as possible until the gas cloud has passed.
(viii) Supports, and parties bringing up ammunition and grenades, will only be moved up if the tactical situation demands.
(ix) The blanket doorways of protected dugouts will be properly adjusted.
(x) Men in charge of combustibles and fans will prepare to use them as soon as the gas cloud has passed, so as to admit of helmets being removed.
(xi) Helmets will not be removed after a gas attack until permission has been given by the company commander, who will ascertain from officers and N. C. O.'s trained at the divisional gas school that it is safe to do so. Trenches will be fanned clear of gas with fans and sandbags.
(xii) In order to guard against the danger of a subsequent gas cloud, all ranks, as soon as the gas is clear and permission has been received to remove their masks, will replace them in the "alert" position.
A sharp lookout will be maintained as long as the wind continues in a dangerous quarter, and men will sleep on the fire step, within reach of a sentry. A subsequent gas cloud is always likely.
(xiii) Dugouts will not be entered for at least four hours after a gas attack, and should be ventilated freely. Ventilation (natural or by means of fires and antigas fans) is the only sure method of clearing a dugout. If dugouts have to be entered owing to heavy shelling, this should be done with the utmost caution, and gas helmets put on at the slightest trace of gas. The clearing of dugouts should not be carried out by men who have been even slightly affected by gas. Dugouts can be efficiently ventilated by means of a small fire burning in the center of a dugout or cellar for 20 minutes. This method has been proved by experiments to be effective, but should be employed with due regard to the danger of smoke being visible to the enemy. Dry wood or other combustibles will be kept in readiness for the purpose.