Moving to Maine as a journeyman HVAC technician: every state's rule

Maine does not issue a journeyman HVAC, air conditioning or refrigeration license, and no Maine city or town was found to do so either; the Office of Professional and Occupational Regulation's list of licensed professions contains no HVAC or mechanical trade. What Maine does license is the fuel side of heating: the Maine Fuel Board issues Journeyman Oil Burner and/or Solid Fuel Technician licenses ($100 plus a $21 background check, exam required, after one year as a licensed apprentice or 160 hours of approved coursework plus six months of apprenticeship) and Propane and Natural Gas Technician licenses ($100 plus $21, board-approved training plus a Fuel Board exam), and anyone who installs or services oil, propane, natural gas or solid-fuel burning equipment must hold one. Ductwork, air conditioning, refrigeration and the mechanical parts of a heat pump need no state license; the electrical connection of a heat pump must be made by a licensed electrician (or, for mini-splits of 36,000 BTU or less in one- and two-family dwellings, by a licensed oil burner technician under a 2013 memorandum of understanding), and the installer needs federal EPA Section 608 refrigerant certification if the system is not factory charged. An out-of-state journeyman HVAC license therefore has nothing to transfer to; the technician may work for any employer without a Maine credential, but must obtain the relevant Fuel Board license before touching a furnace, boiler or gas appliance, and Fuel Board rules give out-of-state applicants no exam waiver, only credit for documented employment as a technician (a statutory endorsement process under 10 M.R.S. s. 8003-H exists but the board has not published a procedure). EPA Section 608 certification is federal and required everywhere for refrigerant handling.