"WIND-SAFE" period.—When the wind is safe working parties during work and at the discretion of the officer in command may take off their box respirators, provided the latter are placed conveniently at hand for use in case of a sudden gas-shell attack or change of the wind.
The P. H. helmet will always be carried.
24. VERMOREL SPRAYERS.—(a) Vermorel sprayers form part of trench stores. They are provided for spraying the blankets of gas-proof dugouts and shelters.
(b) They will be stored in the gas-proof dugout or in a protected position close at hand.
(c) They must be kept one-third full of water. Six gallons of the solution given below to be used in them must be kept in corked jars or petrol tins close to each sprayer. It must not be kept in the sprayer owing to its corrosive nature, and after solution has been used the sprayer must be washed out with water:
Water.—3 gallons (one large bucket);
Sodium thiosulphate (hypo).—1½ lbs. (¾ mess tin);
Sodium carbonate (washing soda).—3 lbs. (one piled mess tin).
(d) Vermorel sprayers will be in charge of company gas N. C. O.'s, who will detail and train men in their care and use and superintend all spraying. The blankets on all gas-protected dugouts will be inspected and sprayed at the commencement of a wind-dangerous period and as often as is necessary to keep them in a moist condition during it.
(e) Company gas N. C. O.'s will take over Vermorel sprayers from outgoing N. C. O.'s.
(f) Vermorel sprayers in the line will on no account be used for clearing gas from trenches or dugouts after an attack. Against the present gas used by the enemy these chemicals have no effect, and Ayrton fans and fires are the means to be used.
The sprayers at medical aid posts are provided with a chemical solution which will clear any gas that may have entered their protected posts.