District of Columbia, DC: EPA's radon zone, explained

District of Columbia is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. District of Columbia sits at the 32nd percentile nationally for radon potential — above 32 of every 100 rated counties.

Where District of Columbia sits nationally

District of Columbia, District of Columbia is home to about 702,250 people across 61.127 square miles. Averaged across its land area, District of Columbia runs about 11,488 people per square mile. By population, District of Columbia is the 42nd largest of every county sharing its EPA zone — the 96th percentile by population within that zone. Geologically, District of Columbia is grouped into EPA Region 3 alongside 244 other counties that share its rock and soil setting.

Zone vs. an actual test

A Zone 3 county like District of Columbia is predicted closer to the 0.4 pCi/L typical outdoors than to EPA's 4 pCi/L action level. Low doesn't mean zero: EPA's own data shows homes in Zone 3 counties like District of Columbia testing above the action level often enough that skipping a test isn't the safe assumption.

Testing and mitigation in District of Columbia

For a District of Columbia 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 District of Columbia's state radon program

For District of Columbia, an ongoing number beats a one-time test - a Airthings radon monitor tracks District of Columbia's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

Where District of Columbia's figures come from

District of Columbia's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone District of Columbia carries, the zone explainer covers what it does and doesn't tell you about any one house.