PRESSURISATION
CS 25.841 Pressurised cabins

(a) Pressurised cabins and compartments to be occupied must be equipped to provide a cabin pressure altitude of not more than 2 438 m (8000 ft) at the maximum operating altitude of the aeroplane under normal operating conditions. If certification for operation over 7 620 m (25 000 ft) is requested, the aeroplane must be able to maintain a cabin pressure altitude of not more than 4572 m (15 000 ft) in the event of any reasonably probable failure or malfunction in the pressurisation system.

Note: 10 000 ft is the cabin altitude at which we might expect a healthy adult to be affected by hypoxia. 6 000 to 8 000 ft maimum cabin pressure altitude will give a comfortable safety margin to account for "non-healthy" passengers.