Nuclear Fallout Shelter Guide: How to Find, Build, and Provision One
Quick Actions
- Go Underground: A basement or subterranean level provides the best protection from fallout radiation.
- Move to the Center: Position yourself as far from exterior walls and the roof as possible.
- Seal the Space: Use plastic sheeting and duct tape to seal windows, doors, and vents.
- Stay for 24–48 Hours: Do not leave your shelter until official authorities declare it safe.
Table of Contents
What Is Nuclear Fallout?
Nuclear fallout is the radioactive material that is propelled into the atmosphere by a nuclear detonation and then falls back to earth. It consists of fine particles of radioactive dust, ash, and debris that can travel hundreds of miles from the point of detonation, depending on wind patterns and the altitude of the explosion.
The danger from fallout is primarily from gamma radiation, which can penetrate the human body from a distance, and from beta particles, which cause severe burns if they contact the skin. The good news is that dense materials — concrete, brick, earth, and even water — are effective at blocking these types of radiation.
Official Source: "Fallout is most dangerous in the first few hours after the detonation when it is giving off the highest levels of radiation." — FEMA Ready.gov
Best Types of Fallout Shelters
The effectiveness of a shelter is measured by its Protection Factor (PF). A PF of 10 means that a person inside the shelter receives one-tenth of the radiation dose they would receive outside. FEMA recommends seeking shelter with the highest PF available.
Radiation Shielding: What Materials Work
Gamma radiation is blocked by mass. The denser and thicker the material, the better it shields against radiation. According to the CDC's radiation emergency guidance, the following materials are effective shields:
- Concrete: 10 inches of concrete reduces gamma radiation by a factor of 10.
- Brick: Similar to concrete. A standard brick wall provides significant protection.
- Earth/Soil: 24 inches of packed earth provides substantial shielding.
- Water: 24 inches of water provides shielding comparable to concrete.
- Lead: The most efficient material, but impractical for most civilians.
- Steel: Effective but heavy. Not practical for improvised shelters.
Key Principle: Put as much dense material as possible between yourself and the outside. Moving to the center of a building and going underground are the two most effective actions you can take without any special materials.
Building an Improvised Fallout Shelter
If you cannot reach a purpose-built shelter, you can significantly improve your protection in any building by following these steps from the FEMA Nuclear Detonation Planning Guide:
- Move to the basement or the most interior room on the lowest floor.
- Seal all windows, doors, and vents with heavy plastic sheeting and duct tape to prevent radioactive dust from entering.
- If possible, stack heavy furniture, books, or sandbags against exterior walls to increase shielding mass.
- Turn off all ventilation systems, air conditioners, and fans that draw outside air in.
- Fill bathtubs, sinks, and any available containers with water before the fallout arrives.
Shelter Supplies: 14-Day Checklist
FEMA recommends preparing for a minimum of 14 days of self-sufficiency inside your shelter. The following checklist is based on the FEMA Emergency Supply Kit guidelines.
- Water: 1 gallon per person per day (14-day minimum)
- Food: Non-perishable, no-cook food for 14 days. Canned goods, protein bars, dried fruit.
- Manual can opener
- Battery-powered or hand-crank NOAA radio
- Flashlights and extra batteries
- First aid kit with a 30-day supply of prescription medications
- Plastic sheeting and duct tape for sealing the shelter
- Heavy-duty garbage bags for waste management
- Sanitation supplies: toilet paper, hand sanitizer, soap
- Copies of important documents in a waterproof container
- Cash in small bills (ATMs and card readers will not work)
- Radiation dosimeter or Geiger counter if available