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I just stupidly dropped my helmet on the floor from a quite high distance. I know (or rather, heard of) that motorbike helmets must be inspected in such cases.

Is it the same for bike helmets? How can I tell if it is still safe?

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1  
How high is "quite high"? Though the canonical advice is, of course, "replace it", I'd not be too worried about a helmet that dropped from 6 feet or so, so long as a reasonably close inspection reveals nothing. –  Daniel R Hicks Nov 5 '13 at 21:21
    
I wonder if physical analysis of the energies involved can approximately be carried out. After all, a helmet has far less mass than a helmet + rider. –  Vorac Nov 6 '13 at 8:03
    
@Daniel it is indeed around 6 feet. A quick inspection revealed very small irregularities, small cracks in the foam, at the spot which I suspect hit the floor. For now I'm inclined to think that it is damaged, but it is true that it still looks new from the outside... –  Antoine_935 Nov 6 '13 at 21:15

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up vote 14 down vote accepted

BHSI.org says the following:

Did you drop it hard enough to crack the foam? Replace.

For starters, most people are aware that you must replace a helmet after any crash where your head hit. The foam part of a helmet is made for one-time use, and after crushing once it is no longer as protective as it was, even if it still looks intact. Bear in mind that if the helmet did its job most people would tell you that they did not even hit their head, or did not hit their head that hard. And the thin shells on most helmets now tend to hide any dents in the foam. But if you can see marks on the shell or measure any foam crush at all, replace the helmet. (Helmets made of EPP foam do recover, but there are few EPP helmets on the market. Yours is EPS or EPU unless otherwise labeled.)

You can also crack the helmet foam or damage it by dropping the helmet on a hard surface. The cracks may be small and hard to see, so you need to look carefully. Cracks in the foam always require replacement of the helmet.

You may be reluctant to replace a helmet that looks almost as good as new, but if you did hit, you don't want to take chances on where you will hit next time. If the foam is cracked under the thin shell, it will be more likely to fly apart in your next crash. Many manufacturers will replace crashed helmets for a nominal fee, and most will also inspect crashed helmets to see if they need replacement. Call them if you are in doubt.

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It seems to be slightly, very lightly cracked, but honestly this could even be a factory defect... The outer shell looks ok. Any idea of how smooth the foam surface should be? –  Antoine_935 Nov 5 '13 at 20:05
    
At the same time I don't see any crack anywhere else, and this is the supposed impact zone... –  Antoine_935 Nov 5 '13 at 20:08
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@Antoine_935 - I very seriously doubt the crack you see is a factory defect. Any cracks should have been caught by the factory's QA process and they would not sell the helmet. –  Carey Gregory Nov 7 '13 at 0:00

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