<P> Often survival practitioners will carry with them a "survival kit". This consists of various items that seem necessary or useful for potential survival situations, depending on anticipated challenges and location . Supplies in a survival kit vary greatly by anticipated needs . For wilderness survival, they often contain items like a knife, water container, fire starting apparatus, first aid equipment, food obtaining devices (snare wire, fish hooks, firearms, or other,) a light, navigational aids, and signalling or communications devices . Often these items will have multiple possible uses as space and weight are often at a premium . </P> <P> Survival kits may be purchased from various retailers or individual components may be bought and assembled into a kit . </P> <P> Some survival books promote the "Universal Edibility Test". Allegedly, it is possible to distinguish edible foods from toxic ones by a series of progressive exposures to skin and mouth prior to ingestion, with waiting periods and checks for symptoms . However, many experts including Ray Mears and John Kallas reject this method, stating that even a small amount of some "potential foods" can cause physical discomfort, illness, or death . </P> <P> Many mainstream survival experts have recommended the act of drinking urine in times of dehydration and malnutrition . However, the United States Air Force Survival Manual (AF 64 - 4) instructs that this technique is a myth and should never be applied . Several reasons for not drinking urine include the high salt content of urine, potential contaminants, and sometimes bacteria growth, despite urine's being generally "sterile". </P>

Survival skills to be adopted for common incidents in school