In Ohio, yes. Radon mitigation contractors must be licensed under ORC 3723.02 through the Ohio Department of Health Radon Licensing Program. In Kentucky, the installer must be certified under KRS 309.430 to 309.454, which the Kentucky Board of Radon Safety enforces.
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This is one of the few home services where the credential question has a clean answer, and it is worth using. In Ohio, radon mitigation is licensed work. Contractors must be licensed under ORC 3723.02 through the Ohio Department of Health Radon Licensing Program, and the license is verifiable. Installed systems follow ANSI/AARST SGM-SF-2023, the national consensus standard for mitigation in existing homes, which governs everything from suction point sizing to where the discharge stack terminates relative to the eave line and to openable windows. Across the river in Kentucky, covering Boone, Kenton, and Campbell counties, radon mitigation requires certification under KRS 309.430 to 309.454, which the Kentucky Board of Radon Safety enforces. The technical standard is the same ANSI/AARST SGM-SF-2023. A contractor working both sides of this market should be able to show you the credential that applies on your side of the line, and being asked is normal. All contractors you work with here are credentialed and insured for this work, and asking any contractor for the number is a reasonable thing to do before signing. On permits: mitigation itself often does not require a building permit, though electrical work for the fan circuit can, and requirements vary by jurisdiction across Hamilton, Butler, Warren, and Clermont counties. Permit requirements for the electrical portion of a mitigation install are set by the local building department, so confirm with the jurisdiction the property sits in. Two things worth requiring in writing regardless of credential: the post-mitigation test result, and the guaranteed level the system is designed to achieve. A quote that omits post-mitigation testing is quoting a different job than the one you want.