CT is correct,
No M rated helmet is flame proof.
I might just chip in here as our company was part of a massive project on bike and helmet safety and I know a fair bit about helmets now as a result.
Nearly all manufacturers actually manufacture their M & SA helmets the same. Costs being costs...
To get a Snell rating both types of helmets undergo the same testing for road impact. SA helmets undergo an additional test for impact into a roll bar / steering wheel & have a nomex inner lining, that's the part that is flame-proof, not the helmet itself.
An M rated helmet will nearly always pass the same roll bar test that an SA helmet will, as stated they are normally manufactured the same.The other difference is that the "specifically" manufactured SA helmets have normally got a smaller eye hole than bike helmets.
On an aside if you want to see the physics, the forces generated when you are levered off a bike onto the road from a high-side at 100khm hitting say a kerb edge, are actually greater than those getting your head wacked into a roll bar while seated. This is why our ASA standard is so strict. Stricter than SNELL I might add
Matter of fact I would rather pop a full face ASA helmet on my head with a nomex hood than a SA rated SNELL open face. Call me funny but if your worried about smashing your face into a steering wheel then anything less than full face seems stupid.
I've seen the results of open face at 60kmh on the Targa Tasmania and was not pretty.
BTW you can get carbon fibre helmets cheaper than that from bike shops.
