Check the reviewed permit path.

Philadelphia

Mechanical permit or EZ mechanical permit check for HVAC replacement

Philadelphia L&I says a Mechanical Permit is needed for heating, venting, air conditioning, ductwork, and equipment or piping that uses natural gas, while some mechanical work such as replacing appliances in one-or-two-family dwellings can be eligible for an EZ permit without plans. HVAC replacement should be confirmed with L&I because the permit route depends on equipment, ductwork, gas piping, electrical power, penetrations, capacity, historic conditions, and whether the work fits an EZ standard.