Section 28-4201 - Proficiency requirement(a) No person or company shall conduct or offer to conduct radon screening, testing, or mitigation in the District for a fee unless the person who performs the service has been: (1) Listed as proficient by the Environmental Protection Agency to offer radon screening, testing, or mitigation services; or(2) Has received a certificate of proficiency from an organization approved by the Mayor to offer radon screening, testing, or mitigation services.(b) The Mayor shall maintain, revise as necessary, and make available to the public a list of persons or companies who have been listed as proficient by the United States Environmental Protection Agency to offer screening, testing, or mitigation for radon.Mar. 13, 1993, D.C. Law 9-183, § 2(b), 39 DCR 8206; Dec. 17, 2014, D.C. Law 20-142, § 201(a), 61 DCR 8045.Applicability of D.C. Law 20-142: Section 502(b) of D.C. Law 20-142 provided that § 201 of the act shall apply as of December 17, 2014.