General Information About Helmet
The helmet protection is provided by the white substance called Expanded Polystyrene (EPS) commonly referred to as "Styrofoam". This is made of a soft, crush able padded material. This dense layer cushions and absorbs the shock as the helmet stops and the head tries to continue moving.The EPS itself needs to be protected because of its poor resistance to abrasion and penetration from sharp objects. It needs to be armored with a more rigid outer shell.
The outer shell is manufactured out of a harder material (generally ABS, Poly carbonate or a fiber/resin composite) design to spread an impact load and make more EPS air cells work for you. Better and stronger material can be used to make thinner and lighter shells but provide a similar overall protection. The shell's smooth round shape will help deflect an impact and extend the deceleration distance and reduce the risk of neck injuries. Fiber/Resin composites are made of glass fibers (fiberglass), aramid fibers (Kevlar), carbon fibers or a mix of the above, bonded together by a plastic resin.
The comfort liner is made out of soft foam and fabric. it fills the gap between your head and the harder and less comfortable EPS. It keeps the helmet in position on your head and reduces wind noise but offers no protection. The retention strap is a safety device used to prevent the helmet from being ejected in a sudden acceleration or deceleration. The safety retention strap should not be too tight but it should be snug enough to keep the helmet from shifting whenever you ride.
External pieces such as vents, side plates and shield are designed to break away or dislocate if excessive force is applied so they do not hook an obstacle or interfere in a case of a slide.