https://www.sportys.com/blog/pilots-guide-portable-oxygen-systems/?

extrait

Why should pilots use oxygen?

Increase Pilot Safety

Hypoxia is a far more common problem than most pilots admit, and is not limited to pilots of turbocharged or high performance aircraft. Many pilots need oxygen below the 12,500 feet specified in the FARs, especially at night. Carrying a portable oxygen system is the only way to protect against the serious and difficult-to-detect symptoms of hypoxia.

Increase Passenger Comfort

Do you or your passengers always arrive tired or with a headache? It’s probably because of mild hypoxia. Spending a few hours at 10,000 feet is often enough to cause significant discomfort. And on average, women need oxygen 2,000 feet lower than men. An oxygen system can help you and your passengers arrive comfortably.

Increase your aircraft’s utility

When 12,500 is no longer a barrier, you can truly make the most of your high performance airplane. You’ll be able to out-climb turbulence or weather, make use of favorable tailwinds, and even enjoy the lighter traffic between 10,000 and 20,000 feet.