In daily life, some people may throw cigarette butts, fruit peel or other rubbish in the elevator. The passenger elevator will also be used to transport construction materials. Therefore some garbage such as broken bricks, cement, dust and so on would be left in the elevator.
But people don't know that garbage or dust is a potential risk for an elevator. Garbage not only makes elevator unsanitary but also unsafe. Many times the elevator's running failure was caused by garbage. This is because before starting the elevator will automatically check whether the door is closed. It would not start if the door is not closed completely.