To get blood out of fabrics, soak them in salt water. You want to avoid soaps, shampoos, detergents etc as well as plain water because these things will tend to rupture the red blood cells and let the red color out. If you soak it in salt water, the red blood cells will diffuse out of the fabric into solution without rupturing, taking all the red color with them. However I don't know how one would use this on a carpet 😕