PURPOSE: To carry out maintenance works for a dome-shaped large-sized building, for example washing or exterior painting, without provision of scaffold and with no workers stationed at high place, by using an arrangement consisting of a ballon helt in the upper sky, pulleys fixed to it, a driving rope, maintenance tools, etc.
CONSTITUTION: Ropes 4 are threaded around pulleys 3, and most portion of a long rope part 11 is drawn into No.1 payoff device, and He gas is supplied into a ballon 2. No.1 ground machine 8 is directed so that its advancing direction is perpendicularly intersecting No.1 line tying the center of a large-sized building 1 concerned to this No.1 ground machine 8. Then No.2 and No.3 ground machines 8 are moved to the optimum points on No.2, No.3 lines where the angle to the No.1 line as the center of the building 1 becomes +120 degs., and the advancing direction is allowed to perpendicularly intersect them. Then the ropes 4 are pulled, and the ballon 2 is sunk to a specified altitude. The water sent via a hose 7 is scattered from a nozzle over the dome surface while the maintenance tools 5 are moved by the ropes 4, and the scatter medium is changed to detergent and moving scatter is carried out.