Kerosene or white spirit (Shellite) stoves with a pump are best for cold conditions. Gas stoves will not work satisfactorily because the liquefied gas will not vaporise in cold conditions. It is essential to carry sufficient spare fuel, as a lot of heat is required to melt snow for cooking and drinking purposes. A 20 × 30 cm piece of three-ply timber or cork placed under the stove will stop it disappearing into the snow. Kerosene stoves will require more priming than usual, and some white spirit stoves also need priming when used below zero. Stores must always be lit entirely outside the tent. Cooking should be done with the stove completely outside the tent or in the vestibule. Never, ever cook inside the inner tent.