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Will a helmet suffer in any way if it is kept in its original box indoors for some years before ever being used? For instance, I might keep it unused for 5 years and then use it for 5 years.
I ask because I own a helmet that I find very comfortable, but the model has been discontinued. I have noticed some end-of-line stock and I might buy more than one, so long as it is perfectly OK to keep a helmet unused for a long time.
There is a common "fact" out there that you should replace a helmet after 5 years, regardless of use or crashes as there is concern that the crush properties of the foam may have changed (e.g., hardening) which could provide less protection.
However the data doesn't seem to bare this out. A recent study did extensive testing of hundreds of used helmets collected from the general public showed that there was no relevant impact performance change with age. The helmets tested had been used but showed no signs of damage and were manufactured between 1987 and 2013.
These results show that if your helmet is not damaged there is no need to replace it simply because of aging. Now likely at some point there is an upper limit whereafter a given age it will need to be replaced, however that limit appears to be well beyond 5 years (some of the tested helmets were over 25 years old - and they still passed crash testing). The most important thing appears that they have been certified under a recent standard and the helmet is not recalled.
A scientific study has found age makes not difference to the protection provided by a bicycle helmet. The study took 63 used and unused, but not crashed, helmets and tested them. Ultimately it reported "Based on these data, the impact attenuation properties of EPS foam in field-used bicycle helmets do not degrade with the age."
Refer The Journal of Biomechanical Engineering.
Detail in case link breaks.
Age Does Not Affect the Material Properties of Expanded Polystyrene Liners in Field-Used Bicycle Helmets
Shannon G. Kroeker, Stephanie J. Bonin, Alyssa L. DeMarco, Craig A. Good and Gunter P. Siegmund
Author and Article Information:
J Biomech Eng 138(4), 041005 (Mar 03, 2016) (9 pages)
Paper No: BIO-15-1567;
A helmet in storage should last decades, provided:
There may also be a slight chance that certain insects would infest the foam, if stored in a buggy shed or some such. (But storing with moth balls would be a bad idea, as the moth balls release fumes.)
I generally refuse to post any kind of claim without the source, but I will throw this much out until I can relocate the source and post it. One factor that will affect thermoplastic or polycarbonate helmets over a period of time is ultraviolet (e.g. sunlight), and some resins in laminated helmets are also susceptible. This will degrade these materials, as well as the foam inside the helmet, and even significant degradation isn't necessarily visible in the shell. So if perchance the helmet is stored with UV exposure over a long period of time, I would be careful. I realize that this scenario isn't probable, just something to consider. If you are planning to store your new helmet indoors, then no problem.
