Check the door for fatigue – Look for damage or structural defects especially on older doors.
Emergency Release – If a door comes down it can possibly trap a child or a small animal. There should be an emergency release cable to disengage the automatic operator and allow a homeowner to lift the door and release whomever is trapped.
Pressure Release – With the door completely open place a 2×4 flat and close the door. As it hits the 2×4 it should sense the pressure and reverse direction.
Photo eyes – Make sure the eyes are present on doors that have been installed since 1992 (if the date is known). These eyes should be located near the floor (generally within 4”-6”). With the door lowering, swing your leg or some other object between the photo eyes and the door should reverse.
Wall Button – The button should be at least five feet above the standing surface and high enough to be out of reach of small children.
Safety Cables – Are the springs restrained be safety cables in the event that the springs break? If a spring breaks the safety cable will help to keep metal parts from flying through the air. Torsion springs will not need these safety cables as the torsion bar works as a containment device.
While these are the major concerns to check, make sure that you look at all moving parts and the overall door condition.