It's a common misconception that we use both nostrils all of the time while breathing. It just isn't so. Jason Kottke is lamenting how he has a cold and can only breathe out of a single nostril. But he's wrong to think this is unusual. To all of you healthy people out there... test it out. Breathe through your nose and check to see if it is coming out of both nostrils. Mine's currently just using the right one.. but I'll give it a few minutes and it will likely switch.