Air conditioners are fixtures (a part of the building). The building owner is responsible for fixtures. DEFINITION OF A FIXTURE: A fixture is defined by weight and attachment. So, a small bird bath could be chattle (personal property), but a large bird bath is heavy, so it is a fixture. A door is a fixture, and the lock in the door is a fixture. Though a key is small and portable, it is attached (meaning a component of) to the lock, so it is part of the fixture. A tree is a fixture (because it is affixed permanently to the ground and it is heavy). A portable potted plant is chattle (because it is small, light, and can be moved). Light bulbs are chattle (so tenants are responsible if they burn out, and, lacking verbiage in the rental agreement, can all be taken by the tenant when he/she moves). My years of real estate college courses are in California, but the fixture law likely applies in your state, as well.