Sprinkle cornstarch, baby powder or baking soda over the spot. Use your fingers to gently rub it into the carpet. Wait about an hour, and then vacuum the spot with a vacuum cleaner attachment hose. Avoid using a beater bar when vacuuming the carpet, as this can grind the ash in more.
Moisten a clean white rag with dry cleaning solvent. Dab the solvent onto the ash spot.
Blot the area with a clean rag to absorb the liquid. Alternate dabbing on the dry cleaning solvent and blotting with a dry rag until the ash is gone.
Rinse the carpet with a clean rag and water. Blot with a dry rag to remove the excess moisture.