Pre smoking ban, regulation required airlines to change air more regularly (every 3 minutes I believe). Now they change it with half-new half-reused air. From

Pre smoking ban, regulation required airlines to change air more regularly (every 3 minutes I believe). Now they change it with half-new half-reused air. From the article: > They don't change the air as regularly, as it costs money to bring fresh subzero air in from outside and heat it to cabin temperature. By the time you reach your destination the percentage of carbon dioxide in the cabin from breathing is much higher than it should be.