Stain Removal Tip for Soot:

For soot, including graphite and copier material: Vacuum using crevice tool of vacuum cleaner. If vacuuming does not remove all or most of the soot, call a professional cleaner.

If vacuuming has removed all particles, apply isopropyl rubbing alcohol to a clean white cloth, white paper towel or cotton ball. If the spot extends deep into the pile, use a blotting motion until the spot is removed or no color is transferred to the cloth. Do not allow the alcohol to penetrate into the backing as this will destroy the latex bond. If the spot is on the surface only, rub in one direction at a time. If this procedure removes the spot, rinse as indicated above and you are finished. If not, go to Step 3.

REMEMBER! Never use a circular motion to remove a spot as this may destroy the texture in the spot area.

Source: Wear-Dated Carpet Spot Cleaning Guide