How long do helmets last?

[RolliePollie]

I just replaced my Bell helmet after about 3-1/2 years. However, my reasoning really had nothing to do with safety, but rather two other factors:

1 - that old helmet stinks to high heaven and no matter what I do, it still stinks.

2 - the old helmet's chin straps, although I've cleaned them, must be harboring some horrible pimple germs because they are making my jawline and under my chin break out.

Now that I've replaced the thing, I'm glad to read that maybe I should've been replacing it for safety's sake as well!

[PscyclePath]

Helmets are made from extruded polystyrene (EPS), a rigid foamed polymer. EPS is an extremely durable polymer... the same thing they make foam coffee cups from. It does not biodegrade (break down in the environment from exposure to oxygen, ozone, etc.) nor does it photodegrade (break down from exposure to sunlight). It might dissolve if you poured some sort of petroleum solvent or mineral spirit on it, it might melt if you heat it to more than 185 degrees F (85 degrees C), and it will burn if you put it in a fire.

A demonstration that I use in some of my League classes is to take a styrofoam coffee cup (also made of EPS) and talk about how durable it is in the environment (my real job is working for the state EPA). You can take this cup, throw it away, it goes into a landfill. 500 years from now, you could dig up that same cup, wash it & sanitize it, and it would be nearly as good as new. EPS is that durable (or persistent, depending on your view).

Next, I hold the cup up, and crush it in my hand. The plastic is still there, just as good as ever, but as far as putting coffee or any other liquid in that cup, it's just "used up" and unsuitable for that purpose. The same thing goes for your helmet if you crash it. The plastic may look okay, and you might be able to pull it back into some sort of cup shape, but it sure won't hold your coffee. Neither would your crashed helmet work to hold your brains in... and your brain can't heal itself when you hurt it.

So, there's no chemical reason to discard your helmet simply based on the passage of time. The major reasons I've found for replacement (other than the occasional crash) is that some of the non-EPS components can break or wear out... such as the pads inside, the suspension system, or maybe the plastic coating over the EPS foam may fade or peel away.

Tom

[OakLeaf]

Tom, I always read and understood that it was UV plus the acids and oils from skin and hair that degrade the EPS.

If you've ever done beach or river cleanup, you've found pieces of styrofoam coolers or crab pot markers that have been in the sun for extended periods of time. The bonds between the beads are weakened and the EPS is brittle and crumbly.

You've seen EPS cups degraded by petroleum solvents such as lipstick, or by touching them with greasy, oily or gassy hands in the garage. Those burn right through EPS. I understand that petroleum products don't have the same structure as animal fats, but it's plain that SOME oils can degrade it, and I don't like to take a risk quibbling about WHICH oils. Obviously animal fats WILL degrade EPS when exposed to heat - if you've ever reheated food containing cheese in the microwave, in an EPS restaurant tray. Not that I do that any more or encourage anyone else to do it, but most of us oldsters have probably done it in the past. Again, the EPS will be intact when the contents are water-based only (showing that it's not the heat alone that dissolves the EPS, but heat plus animal fat). Does the heat merely accelerate the animal fat's ability to dissolve EPS - so that it will still happen over years at a helmet's normal temperatures? Or does it actually change the reaction somehow? I'm not willing to take the risk that it's the latter.

Plus, many hair pomades, skin moisturizers, and sunscreens that could come in contact with a helmet, DO contain petroleum solvents.

Acids - maybe you did a science experiment in grade school. I've never forgotten how the lemon extract that one student brought in, literally melted the inside of the plastic measuring cup that our third grade teacher was using. At that age and at that distance of years, I don't know what kind of plastic it was, but it definitely could have been clear polystyrene. Again, obviously a much stronger acid than sweat, but I've read that sweat has a pH of 4 to 4.5, and the exposure is constant and very long term unless you rinse your helmet after every ride (which would still leave the oils).

Not a risk I'm willing to take, is the bottom line. I'm lucky to have a local recycler of EPS (in most places, unfortunately, the carbon cost of transporting it is greater than what's recovered by recycling). Even with that, obviously replacing my helmet often isn't totally carbon neutral, but I'm walking and talking because of a helmet I wore - Tulip and Mel's daughter are alive because of their helmets - I'm not taking the risk.



As far as putting it in the landfill, isn't the same thing true of a peanut butter sandwich on organic whole wheat bread? I wouldn't take lack of decomposition in a landfill as an indication of what might happen to something more exposed.

[PscyclePath]

True... Over ten years or so, I haven't seen much chemical degradation of the foam in the batches of helmets I've gone through, though it's a wholly different story with the little cushioning pads, straps, etc. I keep my hair trimmed fairly short, and don't use anything but shampoo and water on it. My helmets' risk are way more physical than chemical ;-) Somebody who uses a lot of other stuff on their hair may very likely have a different experience.

I still wind up replacing my helmet about every year and a half or so, simply because the pads wear out or get really ratty, or I find a "prettier" lid. While I went through a number of helmets in in younger and wilder days, I haven't actually crashed one in a little over three years now, other than getting hit by a drunk driver back last February...

And personally, I wouldn't recycle that cup from the landfill... and certainly not the sandwich. Sanitary landfills aren't really that sanitary, nor are they all that leak-proof. Lots of nasty stuff sitting down there against the liner


Tom