Explanation:
The general rule of keeping materials at least 18 inches away from the ceiling in an office is to allow sprinkler systems to reach and control fires effectively. If materials are stored too close to the top, the sprinklers may not be able to get the flames adequately, and the fire could spread more quickly. By keeping materials at least 18 inches away from the ceiling, the sprinklers have a clear path to reach the fire and minimize its impact. This is an essential aspect of building fire safety and helps protect people and property from the damaging effects of fire.