No. There's clearly duct work between the pressure bleed valves and the cabin air. Enough volume of air to keep 300 people breathing fine without feeling incre

No. There's clearly duct work between the pressure bleed valves and the cabin air. Enough volume of air to keep 300 people breathing fine without feeling incredibly stuffy would be a pretty fast wind at the rear galley of a large jetliner. Air comes in ducts, air goes out ducts. You get fresh air. Both the fresh fraction and the recycled fraction are HEPA filtered. Edit: another comment here says the mean replacement time for air in an airliner is 4 to 5 minutes with a recirculating ratio of about 50%. I'm not sure if that's right, but it feels about right. Imagine your share of the space in the cabin. Think how long you could sit in a sealed cardboard box that size before the CO2 levels started making it feel stuffy. The airliners aren't carrying around hundreds or thousands of kg of lithium hydroxide to scrub the CO2. They're just dumping stale air overboard.