There are loads of helmets that push air across your head, but strangely they get described as 'jey' or 'darkside' or something equally infantile.
Meanwhile, 'proper' MTBers insist on buying helmets that try to distance themselves from road-styled helmets and in the process get a sweaty head just standing in the woods……..
My Hex was one of the worst helmets I ever had, while an old Giro road helmet used to make to make me feel like I had an insect moving around inside it, there was so much air being pushed through.
I've just bought a Bell Variant which is a huge improvement on the Hex.