When lacrimatory gases are used goggles affording mechanical protection may be worn, as these gases are not likely to irritate the lungs, though they sometimes produce sickness. IMPROVISED METHODS If a soldier does not possess one of the official pattern respirators, the following measures will be found useful: 1. Wet and wring out any woolen article, such as a stocking or muffler, so as to form a thick pad large enough to cover the nose and mouth, and press firmly over both. 2. Place in a scarf, stocking or handkerchief, a pad of about three handfuls of earth, preferably damp, and tie it firmly over the mouth and nose. 3. A wet cloth pulled down over the eyes will be found useful as additional protection, especially against certain gases other than chlorine or when the gas is too strong for the ordinary respirator. 4. A stocking, wetted with water and soda solution or tea, folded into eight folds and firmly held or tied over the nose. 5. A sock folded fourfold similarly wetted and held or tied. If the sock or comforter has been soaked in soda solution it will still act efficiently when dry, though if possible, it should be moist. The spare tapes from puttees may be used for tying on the sock. 6. Any loose fabric, such as a sock, sandbag, woolen scarf or comforter, soaked in urine, then wrung out to allow of free breathing and tied tightly over the nose and mouth. In the absence of any other cloths, the flannel waistbands issued for winter use could be used for this purpose. KNAPSACK SPRAYERS Knapsack sprayers are issued for use to clear gases out of the trenches after the cloud has blown over. A man with the sprayer on his back (and wearing his smoke helmet) slowly traverses the trench, working the spray. If this is not done the heavy poisonous gas may linger in the trench for days and be a source of great danger. If supports or reinforcements enter a trench charged with gas, they should be preceded by a man using a sprayer. Sprayers are charged with sodium thiosulphate--more commonly known as "hypo"--6 pounds being dissolved in a bucket of water and a handful of ordinary washing soda added. Garden syringes and buckets may be used if sprayers are not available, but these are not so effective. Sprayers should be charged before they are taken up to the trenches, and should be kept ready for immediate use.