This page lists 131 people and firms with a current radon testing credential whose official record names Maryland. Each row shows the credential number, the issuing body, and its own verification date. The latest record check on this page was October 13, 2026; other records may have been checked earlier. Source: the official file linked on each listing. Verify the number before you hire.
Latest credential check October 13, 2026. Methodology Individual record dates may be earlier.NRPP.NRSB.
Testing listings are people credentialed to measure radon. Mitigation listings are people credentialed to install a reduction system. Some people appear on both lists when the official file says they hold both. The list is ordered by the city or county on each record. That place is where the record is filed, not a promise about where the person works.
Fig. 4 — 130 of 131 listings have a mappable place. 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.
Appendix A
Questions before you hire
How do I verify a radon credential listed for Maryland?
Open the source link on this page and match the name and credential number to the official file. Status can change after a record’s verification date. The latest record check on this page was October 13, 2026; check each record’s date. If the official page disagrees with this directory, trust the official page. We do not invent credential numbers.
Does EPA certify radon contractors?
The U.S. EPA does not certify radon contractors. EPA publishes guidance on finding a qualified radon service provider and points to state programs and national certifications. This directory is not affiliated with EPA. We do not display EPA-certified badges.
What does last verified mean on this page?
Last verified on an individual record is the date we checked its official source. The latest credential check on this page was October 13, 2026; other records may have earlier dates. We refresh the roster monthly. Current means the person appeared as currently credentialed on the source at that record’s verification date. Credentials can expire between refreshes, so follow the source link.
Appendix A.2
Before you hire
Ask who holds the credential printed on this page, and ask them to show the same number. Some firms employ several credentialed people. The listing is the person or firm on the official file, not whoever answers the phone.
Ask what test method or mitigation system they will use for this building. A credential is not a work plan. Testing and mitigation are separate services here, and a person appears on both lists only when the official file says they hold both.
Ask how they will document test results or the finished mitigation system. Keep that document with the credential number you verified. This directory does not score jobs, publish reviews, or collect quotes.
Maryland pages here use current NRPP or NRSB certifications. City pages use the city printed on that record, not a ZIP-radius search. A national certification is not a state license in Maryland. Some states require a separate state credential to work legally. Read the methodology. Credential status can change.