In reply to Tom Briggs:
> That they're only designed to take impact from above?
As opposed to from underneath, where the head is? (added because this is UKC and we are supposed to argue)
I was under the impression that foam helmets such as the Meteor were designed to absorb impacts to the top, back, front, side of the helmet - such as what might happen in a penduluming (is that a word?) fall, or a lead fall with rope behind a leg, and that hard shell helmets, with webbing cradle inside were designed to absorb/deflect blows from above - such as from rockfall.
> Yes - ask Petzl.
http://www.petzl.com/en/outdoor/helmets
Helmets are a crucial piece of safety equipment for a variety of vertical activities. They protect the head against falling objects and against impacts with fixed objects - if the climber's head strikes the cliff in a fall, for example.
Helmets can be constructed in several ways, each with its own set of advantages and disadvantages. Helmets made of expanded polystyrene (METEOR3+) are very light but retain marks from minor impacts. Helmets can be constructed using a hybrid of technologies and materials. The ELIOS' lighter ABS shell with expanded foam liner offers an excellent balance between weight and durability.
Or the BMC?
https://www.thebmc.co.uk/climbing-helmets
Climbing helmets come in 3 different flavours - hardshell, foam and hybrids. In general, foam helmets are best for rock climbing, hardshell best for winter & alpine, whilst hybrids are good all rounders. For foam and hybrid helmets, the more extensive and deeper the foam, the better the protection. Some offer almost as much protection around the rim as on the top of the head. Hardshell helmets offer very little protection towards the rim, but are strong against top impacts.
I have a morbid fascination with this topic, as well as a passing interest in the psychology behind the free choice we all have about whether to wear a helmet or not. Make your own mind up. I'm here now (typing rubbish on the net rather than at work) because I wasn't wearing a helmet.