While reading the book The Survivor’s Club by Ben Sherwood I became aware of the Air Force Rule of 3; which state that in a survival situation you cannot survive:
3 seconds without spirit and hope
3 minutes without air
3 hours without shelter in extreme conditions
3 days without water
3 weeks without food
3 months without companionship or love
These are not hard numbers that stand exactly the same in every situation but are a set of rules so that you will always know your survival priorities and be able to manage your needs.
3 seconds without spirit and hope. This is first and foremost because without the will to survive you cannot live.
3 minutes without air. At three minutes or less deprived of air the average person will go unconscious. At five minutes most hearts will stop, although they can still be resuscitated up to about six minutes but will likely suffer permanent brain damage from the minutes of oxygen depletion. Most deaths occur at six minutes or less.
3 hours without shelter in extreme conditions. The concept of shelter is primarily to keep your survival necessities in order, and shelter and heat depend on your circumstances. Use common sense; if it is the desert and daytime find some shade, if it is winter build a shelter and so forth.
3 days without water. Ready.gov recommends One gallon of water per person per day, for drinking and sanitation. Children, nursing mothers, and sick people may need more water. If you live in a warm weather climate more water may be necessary. Store water tightly in clean plastic containers such as soft drink bottles. Keep at least a three-day supply of water per person. If a person is being lethargic then he can expect to survive a week to ten days; if you are active in anyway or in a warm climate then the number of days will drop dramatically.
3 weeks without food. Actually, if you have water you can generally survive longer than 21 days without food; dependent of course on whether or not you have water, climate, physical condition, and the strain you are putting your body through. The well-known Mahatma Gandhi survived 14 hunger strikes with only sips of water and generally averaging the magic 21 days. According to a 1997 editorial in the British Medical Journal by Peel, who briefly reviewed the available literature regarding human starvation; it generally appears as though humans can survive without any food for 30-40 days, as long as they are properly hydrated. Severe symptoms of starvation begin around 35-40 days. If you do a search on the internet you can find the story of Rita Chretien, a Canadian woman who survived being stranded inside a vehicle in Nevada for 48 days, by eating only some trail mix and candy, and drinking water from a stream.
3 months without companionship or love. How long can we survive on our own without some kind of companionship? This really depends on the person; but we as humanity are hardwired to seek some sort of communalism; it’s just what we as primate types always done. Companionship can pick you up in times of hardship and keep you focused on what is important.