8000' cabin altitude is the max that any commercial aircraft will ever have. The pressure differential achievable depends on the strength of the cabin ribs and skin.

All systems are the same. The cabin is fed bleed air - cooled - and then recirculated. The amount of recirculated air is dependent on the aircraft make & model. At the rear of the aircraft, is a valve that modulates to allow a certain amount of air to escape, thus providing more new bleed air to the cabin. When smoking was still allowed on board, these outflow valves would get so gummed up with nicotine, they had to be thrown out. Now they can be rebuilt if necessary.

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