What happens next?

How to clean soot from brick
Put on rubber gloves to protect your hands during the cleaning process.
Place a drop cloth, tarp or plastic around your work area.
You may want to have some newspaper on hand to help absorb sloshed water, drips from the sponge or wet bottoms of buckets.
While you clean sooty bricks, some soot and ash can dislodge from the fireplace. If you don't put down a protective layer, you will have additional soot stains on your carpet to clean.