Ohio Rev. Code Ann. § 3723.05
(B) No licensed radon mitigation contractor shall do any of the following:
(C) No licensed radon tester, licensed radon mitigation specialist, or licensed radon mitigation contractor involved in the testing of a particular building, or in the provision of advice with respect to a particular building, shall be involved in the performance of mitigation on that building unless the contract for mitigation is in writing and clearly and conspicuously states both of the following: