Radon is a naturally-occurring radioactive gas that can cause lung cancer. To reduce your risk of lung cancer, it’s important to flush your home with fresh air and let radon outside.
This is to describe my observations and how I deal with radon in my home.
Radon, an inert noble gas, is a decay product of uranium in the earth. As a gas, it’s less dense than rocks, but heavier than nitrogen and oxygen, so it tends to enter and dwell in the lowest levels of the home.
With an Ecosense RD200 RadonEye real-time detector, I found that the highest levels of radiation from radon would occur during times of low barometric pressure.
The decay chain looks like this:
Rn-222 (3.8 days) -> Po-218 (3.1 minutes) -> Pb-214 (27 minutes) and At-218 (1.5 seconds) -> Bi-214 (20 minutes) -> Tl-210 (1.3 minutes) and Po-214 (0.1 ms) -> Pb-210 (22 years)
Lead-210 will undergo further decay, but because its half-life is so long, the decay rate is slow. All of the above daughters are metals with fairly rapid decays, so if you inhale a radon atom just before it decays, then you will receive the radiation dose of the chain through Lead-210.
When I inhale the air in my home, let’s consider different fractions of that air:
| Radon that entered | Amount that will decay in the next 4 days | Amount that will decay in the next 12 hours |
|---|---|---|
| today | 1/2 | 8.7% |
| 4 days ago | 1/4 | 4.4% |
| 8 days ago | 1/8 | 2.2% |
| 12 days ago | 1/16 | 1.1% |
| 16 days ago | 1/32 | 0.5% |
Due to the nature of radioactive decay, the newest-to-enter radon produces the bulk of the radiation. If you never change the air in your home, then the full radiation dose will occur inside. If you change the air in your home very fast, then most of the decays will occur outside.
With the real-time detector, I found that most of the time, the radiation level was 1 pCi/l (lower is better), but at times of low atmospheric pressure, could spike to 8 pCi/l (remediation strongly recommended).
Since 8.7% of the radon will decay in the first 12 hours, if I change the air every 12 hours, then I am practically removing the not-yet-decayed 91% of radon to decay outside of my home (and lungs). That would bring an 8 pCi/l spike down to 0.7 pCi/l.
If my cellar has 8-foot-high ceilings, then an 800-square-foot space will have 6400 cubic feet of air volume. To change that volume of air over 12 hours = 720 minutes would require a flow of 9 cubic-feet-per-minute (cfm).