Clean smoke damage by mixing warm water with trisodium phosphate cleaner and then using a sponge to wipe the wall or ceiling vigorously with the solution. Clean the sponged areas with a rag that has been dipped in clean water.
Fill a bucket with 1 gallon of warm water and 1 generous tablespoon of trisodium phosphate. Wearing rubber gloves and goggles, wet the sponge in the solution. Wipe the wall or ceiling with the sponge vigorously, working one area at a time. Rinse each area with a rag dipped in clean water. Continue this process until the entire area is washed and rinsed.
You may have to repeat the washing and rinsing process several times depending on the level of soot buildup and/or charring. Don't oversaturate the walls or let the solution seep between the walls and baseboards, or damage may occur to the drywall. If the smoke damage is not entirely removed by this process, you may need to prime and repaint the ceilings and walls.
Trisodium phosphate is a harsh cleaning agent. Wear gloves at all times when working with it because it can cause severe skin irritation. It can also cause severe eye irritation, so wearing goggles or other protective eyewear is highly recommended as well.