Helmet longevity

[in4]

If this is a daft question move along, but:
Do helmets deteriorate over time in terms of their effectiveness?. I'm not too worried about fashion trends or aesthetics. Does the er, polystyrene deteriorate over time or in particular weather conditions?
Clearly any impact damage is a different matter but otherwise...
Thanks
Ian

[Danneaux]

If this is a daft question move along...

No, it is a logical one.

Do helmets deteriorate over time in terms of their effectiveness?...Does the er, polystyrene deteriorate over time or in particular weather conditions?

Yes, yes they do! Most makers (Bell comes to mind) recommend replacement every three years. I once wrote Bell asking for more particulars and they cited sweat exposure, general knocking around and -- first and foremost -- UV and heat exposure. They told me such can degrade the polysterene beads as well as shell, even on in-molded helmets. They further warned against leaving a helmet in a closed vehicle on a warm or hot day. It seems heat approaching 60°C/140°F can not only affect the polysterene but also the bond that attaches separate shells to the foam underlayment. When I asked if the three-year recommendation was hard and fast, they told me it depended on sun and heat exposure and the general amount of usage over that period of time. They also said a helmet can "look good" but be compromised as a result of age and exposure.

I have three helmets and rotate between them so the sweat in pads can dry out before it is used again, or so a washed helmet can dry. I lose a lot of sweat when riding in hot temperatures and it leaves salt deposits on the straps, which I rinse off after each ride. One helmet is dedicated to desert riding, because I know it will get unusually high UV exposure and so will likely age faster.

After my 4-month European double-crossing in 2014, I gave my helmet away to a hotel staffer in Bucharest before I flew home. That helmet had seen about 18 months' use at home and then saw record heat in Romania and Serbia and got lots of sun and weather exposure. I felt a little guilty giving it away rather than destroying it, but the desk clerk's husband had no helmet at all and regularly rode alongside heavy commuter car traffic, so he needed something more than a hat so something was better than nothing. 

Best,

Dan.

[Danneaux]

Here are some additional links citing different replacement times:

https://helmets.org/replace.htm
https://www.thebellgarage.com/helmets/faq/
https://bikefat.com/is-it-time-to-replace-your-bike-helmet/
https://forums.roadbikereview.com/general-cycling-discussion/helmets-expiration-date-not-347741.html
https://bikerumor.com/2018/08/17/aasq-41-how-long-is-a-helmet-good-for-giro-answers-that-and-more-pt-1/

There's lots more info available on the topic, but these links pretty much cover the more common recommendations.

Best,

Dan.

[mickeg]

I just think when it looks like it has been knocked around a bit, or if it is a bit faded from UV, I put it into semi-retirement.

By semi-retirement, i mean that it becomes a travel helmet that I use for trips.  In general terms I assume that I probably am more likely to damage my helmet when it is in vehicles, hanging from my backpack as I walk through airports, wind blowing it off of the picnic table in a campground, etc.  And I would rather not damage a newer helmet that way so I use my older helmets on trips.  Then after a few trips, it goes in the trash. 

The one I wore on my tour in June and July this past summer went into the trash at the Hostel in Halifax before I flew home.

This is not the ideal way to treat a helmet, under a pannier when I stacked up the luggage on the cart at the airport.

[martinf]

I have three, which I rotate (except on long tours). When not in use, they are stored in a dry, fairly dark and not too hot place.

But I keep them much longer than 3 years, generally until the foam pads start to deteriorate. So maybe I should just count the time of use and replace every 9 years or so.