a) Routine maintenance is the observation, inspection, and simple testing of equipment and its operating status through the eyes, ears, nose, hands, and body of maintenance personnel. Timely detection and resolution of potential faults. Usually, routine maintenance is carried out once every two weeks. 

b) Regular maintenance is the process of thoroughly inspecting, repairing, replacing, and adjusting certain parts of equipment during operation, in order to ensure that the inspected parts meet the necessary standards and fundamentally guarantee the internal quality of the equipment. Usually, regular maintenance is carried out once a month. 

The correct definition is a household elevator. An elevator installed in a private residence for the sole use of a single family member. It can also be installed in buildings that are not used by a single household as a tool for a single household to enter their residence, but the public or other residents inside the building cannot enter and use it.