Chapter 01

Certified radon testers & mitigators

Current credentials for radon testing and mitigation in the United States. Each listing shows a credential number, the issuing body, the date we last checked the official file, and a link to that file. This is a directory, not a contractor. EPA does not certify radon contractors.

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.

4,812current listings

50states with listings

1,236cities and counties

September 13, 2026Latest credential check. Individual record dates may be earlier. Methodology

Chapter 02

Cities and counties with the most listings

Chapter 03

States 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.