Unknown Risk

ZIP Code 99950

Ketchikan Gateway Borough County, Alaska — Ketchikan

What You Should Do

1
Testing is still recommended. Even in low-risk zones, individual homes can have elevated radon due to localized geology, foundation type, and construction factors.
2
If your result is below 2.0 pCi/L, no action is needed. Re-test every 2–5 years, or after major renovations that alter your foundation or ventilation.
3
If your result is 4.0 pCi/L or above, install a mitigation system — even in low-risk zones, some homes require active radon reduction.

EPA Zone Details

ZIP Code99950
CountyKetchikan Gateway Borough
CityKetchikan
StateAlaska (AK)

Source: EPA Map of Radon Zones

Radon & Your Basement in Ketchikan Gateway Borough County

Ketchikan Gateway Borough County is in EPA Zone 3, the lowest risk category. However, basements in any zone can have elevated radon due to local soil conditions, foundation cracks, and construction factors.

Radon concentrations are typically highest in the lowest level of a home. However, radon does not stay confined to the basement — it migrates to upper floors through stairways, HVAC ducts, and gaps in flooring. Even if your basement is unfinished or rarely used, elevated radon there can affect the air quality on your main living floors. Always test on the lowest livable level.

Ketchikan Gateway Borough County Radon Map

Counties colored by EPA radon zone. Red = Zone 1 (high), Orange = Zone 2 (moderate), Green = Zone 3 (low).

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Frequently Asked Questions

What is the radon risk level for ZIP code 99950?

ZIP code 99950 is in Ketchikan Gateway Borough County, Alaska, which is classified as EPA Radon Zone ? (unknown risk). The predicted average indoor radon level is not available pCi/L.

Should I test for radon in 99950?

Yes. The EPA recommends testing all homes for radon regardless of zone. Even in lower-risk areas like 99950, individual homes can have elevated radon.

What county is ZIP code 99950 in?

ZIP code 99950 is in Ketchikan Gateway Borough County, Alaska (AK).

Is it safe to live in ZIP code 99950?

ZIP code 99950 is in a lower-risk EPA Zone 3 area. Most homes in this zone have radon levels below the action level. However, the EPA still recommends testing, as individual homes can have elevated levels due to local geology.

Does radon in the basement affect upper floors in Ketchikan Gateway Borough County?

Yes. Radon enters through the foundation and can migrate to upper floors through stairways, HVAC systems, and structural gaps. While concentrations are typically highest at the lowest level, upper floors in Ketchikan Gateway Borough County homes can still have measurable radon. Always test on the lowest livable floor.

How much does radon mitigation cost in Alaska?

In Alaska, radon mitigation systems typically cost between $800 and $2,500 depending on home size, foundation type, and local labor rates. The most common system (sub-slab depressurization) averages $1,000-$1,500. The fan lasts 10-15 years and costs $150-$300 to replace. Some states offer financial assistance programs for radon mitigation.