Along with the progression of our sport has come an evolution in helmet technology and design. What used to be a bulky and ugly piece of equipment has become a streamlined piece of technology that could one day save your life. Here are some things to keep in mind while you shop for a new lid.
Shells and Liners
Expanded polystyrene, or EPS, is the rigid foam that is used to create the inner lining of most helmets. The liner’s job is to absorb the impact to the head by temporarily deforming or breaking apart upon impact. The frosting on this EPS cake is a protective shell, usually manufactured in one of two ways.
In-mold construction is the process by which a polycarbonate outer shell is bonded to the EPS as the foam liner is formed and results in a lightweight, single-piece design. This thinner outer shell is around one millimeter thick and will deform with slightly less force than a hard-shell helmet. This isn’t necessarily a bad thing as it allows the foam liner to do a better job of absorbing impacts with less force involved. Lyndsey Johnson, helmet product manager at Smith, says, “This construction tends to be lighter weight but slightly less durable to dings and dents from normal wear and tear.”
Hard-shell helmets, also known as injection-molded, are constructed primarily from acrylonitrile butadiene styrene (ABS) plastic. This outer shell is about 2-3 millimeters thick and gets bonded to the EPS liner for a two-piece construction. Oscar Huss, head of product development at POC, points out, “Advantages of the hard-shell helmet are good resistance to penetration and durability as well as the possibility to make full-face helmets.” One downfall of the hard-shell design is that impacts of lesser force will not deform the thick, rigid shell as easily and will therefore cause a more abrupt stop to the head. Depending on the force of the impact, this abrupt stop could cause a minor concussion but the extra protection against major head trauma makes hard shell helmets an attractive choice.
Between the US and Europe, there are two main safety certifications. The US certification (ASTM F 2040) is adhered to on a voluntary basis, while the European market requires that all helmets be certified (CE EN 1077). Both involve testing helmets in vertical drops but from different heights and at different speeds. While it’s generally accepted that the European certification is more rudimentary and easier to pass, it’s not exactly an apples to apples comparison as the European certification also tests the effects of sharp objects on the helmet. This is meant to simulate things such as ski poles and tree branches piercing the outer shell. Be sure to look for one, if not both, certifications when considering a helmet.
It is important to note that both of the previous tests rate helmets based on a vertical impact. While this provides some indication of helmet durability, most impacts to the head come at an angle, putting rotational force on the brain with a potential to cause serious damage. A layer of fluid between the brain and skull provides cushioning and energy absorption to combat this. MIPS AB, a Swedish company founded in 2001, has developed a helmet design based on the human body’s protective capability.
According to CEO Niklas Steenberg, “MIPS imitates the brain’s way of protecting itself by giving the helmet its own low-friction layer between the outer shell and the liner to absorb much of the energy created by an oblique blow to the head.” This simple yet effective design is a great step forward and has been adopted by a number of major helmet companies such as POC and Scott. Look for the MIPS logo.
As with most things, helmets aren’t forever. If you’ve owned a helmet for a number of years and have been lucky enough to not hit your head, you should still consider a replacement. “Similar to a piece of bread left on the counter, the protective materials of a helmet age over time and become more brittle,” says Johnson. “We recommend that users replace their helmet after three years to ensure you are utilizing the best protective qualities.”
Most of the lids on the market today are single-impact models and should be replaced after one considerable blow to the head. POC, however, is one company that produces a large portion of multi-impact models. Huss points out that “both kinds work according to the same principle, to compress an expanded foam liner. But the difference is the multi-impact liner’s ability to recover and maintain almost identical performance over multiple hits.”
Multi-impact models are nice in that you don’t have to replace them as often, but there is no standard by which to test them, and it can be hard to know exactly when their time is up. Hopefully, you aren’t hitting your head that often. If you are, maybe it’s time to make some adjustments to your skiing.