For what its worth, nothing about commercial airplanes is a "closed-air-circulation system". The air is continually refreshed from the outside at a rate of abou

For what its worth, nothing about commercial airplanes is a "closed-air-circulation system". The air is continually refreshed from the outside at a rate of about 20 times per hour. http://www.nbcnews.com/id/34708785/ns/travel-travel_tips/t/airplane-air-not-bad-you-think/#.XijqT0OIZ24 http://www.nbcnews.com/id/34708785/ns/travel-travel_tips/t/a...