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Tools  /  Fallout Shielding   Free

How much does that wall protect you?

Fallout is a gamma-radiation problem, and mass is the answer — every few inches of the right material halves the dose reaching you. This turns a wall or roof of any material into a protection factor, and works backwards to the thickness you need for real shelter. It pairs with the fallout map.

1

Your shielding

The material and total thickness between you and the fallout — roof plus walls.
Peak fallout can hit 100s of R/hr, then decays fast.
2

Thickness for a target

How much of each material reaches a given protection factor.
What the numbers mean. PF 10 = you get 1/10th the outside dose (basic). PF 40 = 1/40th, the classic "adequate fallout shelter" standard. PF 100+ = strong protection for the worst early days. A basement corner below grade, or the center of a large building, already gives a useful head start before you add mass.

Notes

The good news is time is on your side. Fallout radiation follows the 7-10 rule: for every 7-fold increase in time, the dose rate drops about 10×. At 7 hours it's ~1/10th of the 1-hour level; at ~2 days, ~1/100th. So even modest shielding for the first 24-72 hours makes the difference, and staying put beats moving through it. Shielding values are halving thicknesses for fallout gamma (~0.7 MeV, buildup included) — the more mass you put overhead and around you, the better, and combining materials just adds their halving counts. This estimates dose reduction; it is not a substitute for a real dosimeter.