Hiking equipment
According to Tom Brown, the basic plan for survival is in the order of shelter (including clothing), water, fire, and food. Cody Lundin writes about the "Rule of 3s"; this relates to human survival without basics: three minutes without air, three hours without shelter, three days without water, or three weeks without food.
Bottled water
Bottled water is often stored as part of an emergency kit in case of natural disaster. The U.S. Federal Emergency Management Agency (FEMA) says the "safest" and "most reliable" source of drinking water is store bought bottled water. Commonly, disaster management experts recommend storing of water per person, per day for at least three days. This amount is intended to include water for drinking and cooking as well as water for hand washing, washing dishes, and personal hygiene. Factory-containers of water have an indefinite shelf life, as long as they remain unopened and undamaged. The sell-by date is voluntarily and individually set by manufacturers to indicate the length of time that they believe the water will taste and smell fresh, rather than to indicate any issue of contamination or food safety.