eric1115 said:
Ever notice how a styrofoam cooler gets all brittle and weak after several years? Just because your helmet doesn't show any damage doesn't mean that it will still protect your head adequately. I've seen older helmets that have been crashed on.
How old? In direct comparison with newer helmets?
Heat, sweat, UV, and the sands of time will all break down the foam that you trust your life to.
Heat and UV ok, but define "the sands of time"
I do not deny the fact that plastics are undergoing deterioration, however this is dependent on certain factors, mostly sunlight (UV) and temperature variation, but the least reason is passing time itself. And in my - also professional - experience, plastics deterioration is usually clearly visible (change in colour and sometimes embrittled surface).
And black coloration - as used for most helmets inner styrofoam shell - stabilizes plastics against UV. Also the styrofoam - which has to absorb the shock in case of an impact - is covered by an outer shell an thus not directly exposed to sunlight.
The abovementioned styrofoam coolers are usually light-colored and as written by Eric they really do look deteriorated if they are.
Some more thoughts about it:
- Industrial safety helmets (I wear one every week) have to show the production date and can be used a certain time span from this date according to regulations, only thermoplastic ones (made of polyethylene which is definitely UV-sensitive) have to be replaced earlier.
- Why does my bicycle helmet not show a production or "replace after" date?
- Why does Giro still offer the visor for such an old model?
- In
http://www.bellbikehelmets.com/downloads/Bell_Bike_OwnersManual_Multilanguage.pdf
you can read the user manual for bell helmets. They wrote everything in it but the necessity to replace the helmet after a certain time span.
My helmet (as well as my bicycle) has barely been used for 4-5 years (shame on me, I know), stored inside the cupboard in my apartment - no sun, no rain, room temperature. It's really in good condition apart from a few minor scratches and the pads falling apart after a few machine washes. So why not further use it.
On the net I only found vague recommendations for helmet replacement by several organisations, but never backed with reliable sources like (scientific) test results.
So I'm simply not convinced and after careful consideration I still trust in my helmet.
It's easy to tell people not to make any compromises when dealing with safety issues. But if the next one says "replace your helmet every second year", who can prove this wrong? In doubt just buy a new one?
And what's written in
http://www.helmets.org/replace.htm (thanks to timothynyc) largely confirms my thoughts.
Markus
