How To Breathe Easy
You never thought about oxygen during your training until after your advanced ratings years later when you finally started flying at altitudes requiring oxygen. At first you probably just borrowed a portable bottle. Perhaps later you flew a plane with a built-in system. But you never liked that cannula stuck up your nose, so you bought a pressurized twin Cessna 421 with its requisite built-in oxygen system. With pressurization, you again no longer think about oxygen.But…