Some set-in carpet stains are removable. The stain sticks to the fibers and may have been ground farther into the carpet. Both factors make removal difficult. Baking soda lifts stains and whitens fabric fibers. The only way to know if the stain is removable is to try to remove it. Stains on the top of the fibers remove easier than stains that soaked through the bottom of the carpet.
Vacuum the area to remove loose dirt and hair.
Pour 1 cup of baking soda into the salad bowl. Add 2 tbsp. of water and stir. The baking soda and water makes a paste. The paste should be thick, like toothpaste or facial mask cream. Add 1 tbsp. at a time to make a more pasty consistency, if needed.
Scoop the paste of out the bowl with the spoon and set it on the stain. Gently work the paste into the carpet fibers with your fingers. This helps the paste work its way into the fibers without damaging the fibers. Leave the paste on the stain.
Place five to eight paper towels on top of the stain and weight it down with a heavy item. According to Good Housekeeping, this helps soak the stain from the carpet. Vacuum the baking soda crumbs from the carpet.