(1) All windows, glass, partitions, and skylights must be washed as often as necessary to keep them clean. Cracked or broken glass must be replaced promptly. The walls, ceilings, and doors must be washed periodically and kept free from soil and unsightly conditions.   The shelves and ledges must be wiped or vacuumed as often as necessary to keep them free from dust and debris. The material picked up by the vacuum cleaners must be disposed of by burning or other proper methods to destroy any insects that might be present.