I work part time for the blood service and have a CPL/IR, we ask all donors and have a specific list of jobs were if you're going on duty within 24 hrs of donating then we wont take it from you, pilot & ATC are on this list.
We also have pilots in to donate who's employers SOP's dont allow donation at all. MadJock its more to do with vasovagal events ie fainting, which can happen within that 24 hour period, the hemoglobin which carries oxygen in the red blood cells takes about 3 months to be replaced not 24 hours, thats why you cant donate again for 12 weeks after a donation, 16wks for women.
Last edited by Nearly There; 17th Jan 2013 at 14:00.