Ketchikan Gateway Borough, AK: EPA's radon zone, explained

EPA places Ketchikan Gateway Borough in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Ketchikan Gateway Borough sits at the 42nd percentile nationally for radon potential — above 42 of every 100 rated counties.

Where Ketchikan Gateway Borough sits nationally

Ketchikan Gateway Borough, Alaska is home to about 13,677 people across 4,857.091 square miles. That works out to roughly 3 people per square mile. By population, Ketchikan Gateway Borough is the 738th largest of every county sharing its EPA zone — the 29th percentile by population within that zone. Ketchikan Gateway Borough falls in EPA Radon Region 10, one of 142 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Ketchikan Gateway Borough's predicted average falls between EPA's 4 pCi/L action level and the national indoor average of about 1.3 pCi/L (outdoor air runs roughly 0.4 pCi/L). Ketchikan Gateway Borough's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

Testing and mitigation in Ketchikan Gateway Borough

For a Ketchikan Gateway Borough homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Alaska's state radon program

For Ketchikan Gateway Borough, an ongoing number beats a one-time test - a Airthings radon monitor tracks Ketchikan Gateway Borough's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

Where Ketchikan Gateway Borough's figures come from

The methodology guide shows exactly which EPA and Census sources feed Ketchikan Gateway Borough's numbers. Whatever zone Ketchikan Gateway Borough carries, the zone explainer covers what it does and doesn't tell you about any one house.