Chapter 01

Certified radon testers & mitigators

Find radon testing and mitigation professionals in the United States and Canada. Each listing shows a credential number, the issuing body, the date we last checked the official source, and a link to that source.

Search the United States

Opens a city or county we already publish.

Or open a place from a file we import:

Fig. 1 — Each pin is a current listing at the Census city or county centroid on the file, approximate. Pins that share a place are spread so you can click them. Not street addresses.

6,341current US listings

50US states with listings + DC

1,832US cities and counties

September 14, 2026Latest US credential check. Individual record dates may be earlier. Methodology

Chapter 02

US cities and counties with the most listings

Allegheny County, PA Total 84 · testing 79 · mitigation 7
Denver, CO Total 77 · testing 57 · mitigation 20
Colorado Springs, CO Total 72 · testing 58 · mitigation 14
Montgomery County, PA Total 60 · testing 47 · mitigation 17
Louisville, KY Total 53 · testing 33 · mitigation 20
Johnson County, KS Total 42 · testing 41 · mitigation 9
Sedgwick County, KS Total 41 · testing 40 · mitigation 13
Westmont, IL Total 41 · testing 41
Centennial, CO Total 40 · testing 17 · mitigation 23
Littleton, CO Total 40 · testing 25 · mitigation 15
Minneapolis, MN Total 36 · testing 36 · mitigation 5
Indianapolis, IN Total 35 · testing 27 · mitigation 8

Chapter 03

US states and DC with current listings

Who credentials radon work in each state, and where to verify a number, is tabulated in radon credentials by state.

The homeowner’s reference

Before you book, and after the work

Read the homeowner guides for testing timelines, system maintenance and when to retest.