Ha ha, this coming from a guy calling himself "experiment"... 

I tend to agree with Part Time.

Will try the Specialized tho, thanks for the tip.  I must admit, Specialized due seem to put more thought and engineering into their products (for better or worse).  Probably helps that they are a mountain bike only company.

quick question.... where did the 5% figure come from? is it from some scientific study or just an arbitrary value?

if you really need 5% more oxygen in your bloodstream, try cutting down on the fags! 

They've no doubt learnt a bit about you...  It's a forum after all - of course people are gonna contest your ideas and disagree here and there, don't worry about it !

My old Fox made me want to take it off after a run, 'cos I felt I was breathing my own hot air - though I never felt this when riding, I guess 'cos I was moving. My new Giro Remedy though, does not give this feeling at the end of a run. I suspect that some helmets may exhibit the issue the original poster is talking about, but that is not to say all full face lids exhibit that, thus I can't see the need for a "new" design, mealy "better" designs, like the Remedy.

I like how if you don't have the problem, then it must be non-existent...   

It is interesting to me though that there are only a few people who have responded that have experienced the same thing I have.  Anyway, it doesn't have to be a big problem to be improved.  Otherwise we'd all still be riding single pivot bikes...

Oh well, it's been fun discussing.  Would be interesting to see a sports scientist do some research to see if there is any oxygen restriction, however small, from having a chin guard in the air flow.  And maybe some wind tunnel testing of different peak designs.  But that'll never get done with the if it ain't broke don't fix it attitude...so I best be takin' my ideas elsewhere!  Cheers dudes, no hard feelings...   

err... they seem to be still quite popular 

Linkage single pivots for the domination of Al.

Orge.

I'm just struggling to see how you would see a drop in RBC's.
Ok possibly a drop in the O2 stats but there should not be a drop in cell count.