EPA suggests, but will not call for, that wholesalers hold lists of authorized Reps to help you with this particular determination. Wholesalers that provide both ozone-depleting or substitute refrigerants ought to keep invoices that indicate the name of the purchaser, the date of sale, and the amount of refrigerant bought. https://trentonodhpz.amoblog.com/where-to-buy-r407c-refrigerant-secrets-50528706