Because of the intricate nature of the job and since it calls for handling of tools and equipment, performing a valve job which involves the reconditioning of the valves, valve seats and the valve guides ought to be served by a professional. An equipped home mechanic can take off the head and, taking basic cleaning and inspecting, reassemble and send it to the dealer service department or an automotive machine shop, where the actual servicing is to be done. Performing the inspection enables determination of the status of the head and valve train parts and checking on work that may be required and new parts with an automotive machine shop. The dealer service department or the automotive machine shop is responsible for the removal of valves and springs, reconditioning or replacing of valves and valve seats, reconditioning of valve guides, checking and replacing of valve springs, spring retainers and keepers if necessary, replacing new valve seats, reassembling of the valves and determining the correct installed spring height. Also the surface of the cylinder head gasket will be done again in case it is warps. The reconditioning of the valve can only be done by a professional when this is done the head will be as good as new. It is necessary to clean the head with great care at its return on the engine; this step is useful to remove remains of metal or abrasive dust could resulted from the valve service or the process of cylinder head resurfacing Many car manufacturers use compressed air to blow through all the paths and openings of the oil.