David Morton
Lifetime Supporter
Jim,
The cabin air does eventually partly exhaust overboard via a couple of valves (Outflow Valves) operated by the ECS (Environmental Control Systems ) and so it keeps changing. Some aeroplanes are better at it than others.

Outflow and pressure relief valve on a Boeing 737-800
When the airlines permitted smoking the Outflow Valves were always highly contaminated and often malfunctioned as any Nigels (A BA cabin crew term for a Pilot) here will confirm.
So a miss is as good as a mile Jim....
Think on.
Veek,
I am learning Bagpiping and drink Barolo - does that count?
The cabin air does eventually partly exhaust overboard via a couple of valves (Outflow Valves) operated by the ECS (Environmental Control Systems ) and so it keeps changing. Some aeroplanes are better at it than others.


Outflow and pressure relief valve on a Boeing 737-800
When the airlines permitted smoking the Outflow Valves were always highly contaminated and often malfunctioned as any Nigels (A BA cabin crew term for a Pilot) here will confirm.
So a miss is as good as a mile Jim....
Think on.
Veek,
I am learning Bagpiping and drink Barolo - does that count?