Records the law already makes you keep
HVAC refrigerant record keeping requirements, US and GB
Updated
The refrigerant rules are why an HVAC firm's files run deep: they require leak, repair, disposal and certification records to be kept for years.
United States: EPA Section 608
Disposal of 5 to 50 pound appliances
40 CFR 82.156 says technicians evacuating refrigerant from appliances with a full charge of more than 5 and less than 50 pounds for disposal "must keep records documenting the following for three years".
Source: 40 CFR 82.156, refrigerant evacuation and disposal records
Leak inspection and repair
40 CFR 82.157 says: "All records identified in this paragraph must be kept for at least three years in electronic or paper format, unless otherwise specified." Owners or operators keep the leak inspection records.
Source: 40 CFR 82.157
Technician certificates
40 CFR 82.161 says: "Technicians must maintain a copy of their certificate until three years after no longer operating as a technician."
Source: 40 CFR 82.161
Great Britain: the F-gas Regulation and gas safety
F-gas records kept by a servicing firm
Article 6 of Regulation (EU) No 517/2014, as it applies in Great Britain, says undertakings servicing equipment for operators "shall keep copies of the records referred to in paragraph 1 for at least five years".
Source: Regulation (EU) No 517/2014 article 6
Gas safety check records
Regulation 36 of the Gas Safety (Installation and Use) Regulations 1998 keeps a landlord's appliance check record until there have been two further checks of the appliance or flue.
Source: Gas Safety (Installation and Use) Regulations 1998 regulation 36
Refrigerant logs in an HVAC data licence
A record the law makes you keep must still be kept after a licence: the firm licenses a copy, never the original. Records that name a householder or a site are cleaned of personal details before any copy leaves.