Because felt is not a woven fabric the best way to clean these mats is to dry brush them with a soft-bristled brush. If the dry brush doesn't remove the debris then try a damp cloth and gently wipe. If these steps don't work, the mat can be hand-washed (in a sink—not a machine) in cool water with something like Woolite. The mat should soak and the excess water should be gently squeezed (not wrung) out of the material. This soak/squeeze process may need to be repeated (careful not to rub or twist) several times until it is clean. The mat should then be placed on a towel and allowed to air dry.