Do FTs care about the Air Quality on-board during Flights?

I was browseing through this website - and - it has some very intriguing information.

I've been flying a lot this past year due to work - and consequently - I haven't gotten any real illness yet (knock on wood) but I do feel the effects of lag and just general tiredness.

http://www.flyana.com/air.html

Do you FTs usually turn the air nozzle on full blast or do you leave it off because it just sends recirculated air? Or is it really fresh air?