Systems guide

Radon in an underground bunker

Radon is a radioactive gas from uranium in soil and rock. It collects in spaces below ground, and a bunker is about as far below ground as a room gets.

The short answer
  • The EPA action level for radon is 4 pCi/L, and the EPA suggests considering a fix between 2 and 4.
  • In Utah, about 1 in 3 homes tested has had elevated radon.
  • A sealed steel shell plus steady mechanical ventilation is the fix, and testing confirms it.

Why it matters

Radon is a leading cause of lung cancer after smoking, according to the EPA. It has no smell or color, so the only way to know the level is to test. Levels vary from one property to the next, even on the same street.

How a bunker keeps it out

Radon enters buildings through cracks and joints in contact with soil. A welded steel shell with sealed joints has far fewer paths than a block or poured wall with cracks. Mechanical ventilation then replaces the inside air with outside air on a steady schedule, which dilutes whatever does get in.

Testing

  • Test after the bunker is installed and the ventilation is running as it will in use.
  • Use a long-term test for the best picture, or short-term tests in different seasons.
  • Test again after any change to the air system.

Questions

Is radon worse in a bunker than a basement?

It can be, because a bunker is deeper and fully surrounded by soil. A sealed shell and steady ventilation are what keep it low. Test to know.

What level should I aim for?

Below the EPA action level of 4 pCi/L, and below 2 pCi/L where you can.

Sources
  1. U.S. EPA: Health risks of radon (archived)
  2. Utah DEQ: Elevated radon found in 1 in 3 Utah homes tested
  3. Wisconsin Department of Health Services: Radon mitigation

CUBE Bunker prices are preliminary until engineering for the cube system is complete and are confirmed in writing after a site visit. This guide is general information, not engineering, legal or medical advice. Updated 2026-11-02.