You don't have to have a fire in your own home to need a fire damage cleanup. Sometimes the fire can be from the neighbor next door or from a house down the street. Even when wild fires hit the wind can carry the smoke from the fire and bring it through your windows. Then it appears as a grey soot on your walls that sometimes you can see and sometimes you need to wipe it to see it. One thing is for sure even if you can't see it, you will always smell it. Smoke has a very strong smell and will stay on your walls until they are cleaned properly.