SURPRISE: It's fresh air, not circulated stale air.

[abajan]

Haven't most of you always heard/assumed that the cabin air you breath while flying is the same air being recirculated for the duration of the flight? That's why it's so easy to catch colds and whatever else other passengers have. Right?

Well, it seems this was never so. At least that's what I heard on CNN this morning: fresh air is brought in and stale air expelled, pretty much just like any regular air conditioning system on the ground.

Hmm...

[coriolis]

I think that's part true about ground systems. There is a portion that can be recirculated. There are regulations about the required percentage of fresh air. I believe that all air goes through a filter, though.

Here's some FAQs from Boeing.
http://www.boeing.com/commercial/cabinair/facts.html#6

If you're really bored research ASRAE standard 62 which covers ventilation rates, recirculation rates, and diffusion of body odors. (I'm not making that up - that's a parameter for designing HVAC systems)

Bottom line is that a % of air is recirculated the remaining % is fresh.

[breeze]

I've always heard that, and, I turn the air vents away from me.

Good link by Ed, though...ah, but, I'm a creature of habit - I'll still turn
that vent away from me... JUST to be on the safe side!

~Annette~

[abajan]

...Good link by Ed, though...

Agreed. It certainly sheads a lot more light on the matter.