Annulus (firestop)

An annulus (firestop) is something that can help keep a fire from spreading. It's like a big, round ring that goes around walls or other structures that have been built together, like a house or a building. It is made out of materials that won't burn, like metal or special types of rocks and concrete. When the annulus is put in place, it helps to protect the structure from catching fire in the event of a fire. If a fire does start, the annulus can help keep it from spreading and make it so that the fire doesn't do too much damage.