Vacuum the soot-stained carpet with the crevice attachment. Extract as much soot from the flooring as possible.
Tamp the soot-stained carpet with white paper towels to pull more dark powder from the carpet.
Moisten a white cloth or paper towel with isopropyl alcohol. Blot the soot stain with the isopropyl alcohol until it stops transferring onto the cloth or paper towel. Fold the cloth or paper towel to a clean area frequently when blotting.
Examine the carpet for remaining soot. If the soot stain lingers, add 1/4 teaspoon of nonbleach dish detergent to a bowl. Stir 1 quart of water into the detergent.
Dampen another white cloth or paper towel with the soapy solution. Blot the stain until all of the soot is removed. Fold the cloth or paper towel frequently when blotting.
Spritz the carpet with water from a spray bottle. Blot the area with a white towel to absorb as much water as possible.
Cover the moist carpet with another white towel. Place a brick on the towel and leave it overnight.