Where the rule comes from
Search and rescue teams use it as a rough triage aid: roughly three minutes without breathable air, three hours without shelter in harsh conditions, three days without water, three weeks without food. The numbers are approximations, not promises — but the ordering is what matters.
It tells you what to buy first
Most people stockpile food because it feels productive. The rule says otherwise: airway skills and smoke alarms first, then warmth and shelter, then water, then food. Money spent in that order buys far more safety per pound.
The UK version
In a British emergency the realistic threats are smoke, cold, a burst or contaminated mains, and a few days of disrupted shopping. That maps onto the same order: working alarms and first aid, a way to stay warm without power, stored and treatable water, then three days of no-cook food.
Don't take it literally
Age, health, temperature and exertion move every number. Treat it as a priority list, not a countdown clock — and remember that panic and poor decisions kill long before hunger does.
