How long should I plan to stay inside a survival shelter?

The duration of sheltering depends entirely on the threat hierarchy and site-specific conditions. Different hazards require vastly different timelines:

• Short-term events: A tornado or severe storm may require sheltering for just a few hours. Hurricanes or extended flooding events may require days to a week of protection.
• Nuclear fallout: A nuclear detonation or radiological event may require sheltering for two weeks or longer, depending on proximity to the blast and prevailing winds. The “7-10 rule” is a useful guideline: 90% of radiation decays in 7 hours, 99% in 49 hours, and 99.9% in roughly 14 days. Multiple or upwind surface detonations can extend sheltering requirements significantly.
• Civilization-collapse or extreme CBRN events: These could demand sheltering for months if safe conditions outside cannot be assured.

Site factors—such as downwind fallout patterns, local geography, and population density—also influence the required shelter duration. Life-support systems must be sized accordingly: water, air, power, waste management, food, and medical supplies must all sustain the full expected occupancy period. Expert advice, such as from CBRN specialists like Shannon Pack of Andair AG, emphasizes that some sheltering scenarios warrant continued protection outdoors for months after the initial event to avoid residual hazards.

Ultimately, the owner’s programming decisions—threat prioritization, assets to protect, and acceptable risk—will define the exact sheltering duration for a given facility.