Helmets are made of materials that can be damaged by many commonly available cleaners.
Clean the helmet using a soft cloth or sponge, warm water and mild soap. When drying, be careful the helmet doesn't get too hot as this can damage the interior EPS lining. Let dry at room temperature, never close heating appliances as too high temperature will damage the inner liner material and inner shell.
Clean the removable liner hand wash using a towel then permit to air dry whenever it's possible to attenuate heat damage.