The Rule of Threes is a basic concept for survival. It applies in disaster situations and in wilderness survival situations. It is a good way to help prioritize your activities when in survival mode.
Simply put, you can live 3 minutes without air, 3 hours without shelter (in an inhospitable climate), 3 days without water, and 3 weeks without food. Use the "Rule of Threes" to help you prioritize your activities in an emergency situation. In a disaster situation where you have victims injured by falling debris or from falling down (e.g., earthquake, tornado, mudslide, avalanche, building collapse) they may run out of air or their injuries may have stopped their breathing. You will need to clear their airway within 3 minutes and, if they don't start breathing on their own, begin CPR. If you find yourself stranded in an inhospitable environment (cold and wet or very hot), you will need to see shelter or you will be likely to die with 3 hours. If it is cold and wet you will need to find someplace warm and dry. If it is hot you will need to seek shade and ways to remain cool. If you are in a mild climate, shelter may not be such an urgent need. Water will be your next priority. You can live only about 3 days without water. You will being to feel the affects of dehydration much sooner than that and will want to find water as soon as possible. In hot weather you may not even last 3 days without water. Most people will be able to survive about 3 weeks without food. If you are particularly thin or have medical conditions that are sensitive to what you eat (like diabetes or hypoglycemia) you may experience difficulties much sooner. If you have any such conditions you should take steps to ensure you always have timely access to necessary nutrition. Your body fat reserves may affect how quickly you experience dehydration problems too. Especially thin people may feel the effects of lack of water fasting before the end of the 3 days. People with extra fat reserves may be able to last longer than the predicted 3 days. While you can survive for about 3 weeks without food, you will begin to suffer the affects much sooner so it is a good idea to seek nutrition early in a survival situation. Without food your body will begin to tap into your fat reserves and you will find yourself low on energy and discover it is hard to think straight long before the 3 weeks is up. Ever get a "hunger headache"? Sometimes you only need to miss a meal or two before one strikes. And that's nothing compared to the brain fog that can impair your thinking in a survival situation when you go too long without any nutrition.
Knowing you can go three days without water doesn't mean you should. You will begin to suffer the effects of dehydration long before that. Not only are they unpleasant and painful, they will inhibit both your physical and mental ability to take care of yourself. The same is true of food. In a survival situation you will want to start finding something to eat as soon as you can. Although you can live weeks without food, you will quickly loose strength, energy, and clear thought you need to survive. The whole point of the Rule of Threes is to help you prioritize your activities so maximize your chances of survival.
In a survival situation where you are deprived of proper food and water, people often mistake thirst for hunger and waste time seeking food when what they really need to survive and thrive, is water. Remembering the Rule of Threes may help you focus your energies on what is most needed.
Knowing the Rule of Threes will help you prioritize your actions in an emergency situation. Otherwise, you might react to being thirsty or hungry and spend time looking for food and water and ignore the need for shelter until it is too late.
Threes a charm!