Question 1

What is radon?

Accepted Answer

Radon is a colorless, odorless radioactive gas that forms from the natural decay of uranium in soil and rock. It seeps up through the ground and can accumulate inside homes, especially in basements and lower levels. Radon is the second leading cause of lung cancer in the US after smoking, responsible for about 21,000 deaths per year according to the EPA.

Question 2

What do the EPA radon zones mean?

Accepted Answer

The EPA divides US counties into three zones: Zone 1 (predicted average indoor radon above 4 pCi/L — high risk, testing strongly recommended), Zone 2 (2–4 pCi/L — moderate risk, testing recommended), and Zone 3 (below 2 pCi/L — lower risk, but testing is still advised). The EPA action level is 4 pCi/L — above this, the agency recommends mitigation.

Question 3

How do I test my home for radon?

Accepted Answer

Short-term test kits (2–7 days) are available for $15–30 at hardware stores or online. Place the kit in your lowest livable area (usually the basement or first floor) away from windows and vents. Mail it to the lab included with the kit. Long-term test kits (90+ days) give a more accurate annual average. Professional testing by a certified radon tester costs $150–350 and is often required for real estate transactions.

Question 4

What radon level requires action?

Accepted Answer

The EPA recommends fixing your home if radon is at or above 4 pCi/L. Consider mitigation at 2–4 pCi/L. The average US indoor radon level is about 1.3 pCi/L. There is no safe level of radon — it's a risk factor, not a threshold with a safe zone below it.

Question 5

How much does radon mitigation cost?

Accepted Answer

Active sub-slab depressurization — the most common fix — typically costs $800–2,500 depending on your home's foundation type and size. It involves installing a vent pipe through the foundation and a fan to draw radon out before it enters the home. Once installed, ongoing costs are minimal (a small fan running continuously). Most mitigation systems reduce radon levels by 50–99%.

Question 6

Does radon level change with the seasons?

Accepted Answer

Yes. Radon levels tend to be higher in winter when windows are closed and homes are tightly sealed, and lower in summer with more ventilation. Levels also vary by time of day and weather conditions. Long-term tests (90+ days) account for these fluctuations and give a more accurate picture of your year-round average.

Question 7

My area is Zone 3 — do I still need to test?

Accepted Answer

Yes. Even in Zone 3 counties, individual homes can have elevated radon due to local geology, construction type, or soil permeability. The EPA recommends all homes test regardless of zone. Zone classifications are county averages — your specific home could be above or below that average.

Question 8

Does home insurance cover radon mitigation?

Accepted Answer

Typically no — standard homeowners insurance policies exclude radon testing and mitigation. Some states require radon disclosure in real estate transactions, and buyers sometimes negotiate for radon mitigation as part of a sale. Costs are generally tax-deductible only if the home is a rental property.

Lower radon zone in Kirkland, WA — periodic testing still advised

Radon risk in King County, WA

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