The EPS liner doesn’t require maintenance or cleaning, but it benefits from a clean environment. Sweat and skin oil accelerate its breakdown, which is why most helmet manufacturers suggest replacing a helmet at specified intervals after its first use. The comfort liner absorbs contaminants and should be washed regularly to protect the EPS and to keep the helmet from smelling like a soiled gym sock. Use a very mild soap or shampoo that your skin is already used to; avoid scented soaps unless you really like the smell. Rinse out all the soap, wring the moisture out of the liner, and let it air dry.