EPA Section 609 & 608 Certification to Purchase Refrigerant
As of January 01, 2018, Section 609 or 608 Certification is required to Buy Cylinders of Refrigerant. Distributors (sellers) are required to keep records of certified technicians (customers) purchasing refrigerant over 2 pounds.
Link to EPA requirement: https://www.epa.gov/section608/refrigerant-sales-restriction
Links to EPA approved certification programs:
608: (Stationary Appliances)–