Oxygen is the elixir of life. Our body’s cells need it to metabolize. Without enough of it we die. It just so happens that as we ascend in the atmosphere that’s exactly what happens—we get less and less of this vital gas and we suffer from low blood oxygen or hypoxia. Initially judgment is impaired and eventually consciousness is lost. How fast and how badly this happens is a function of altitude. Up at 22,000 feet in an unpressurized cabin, you’re toast in as little as five minutes! So how do you avoid this life-threatening situation inflight?

First, and foremost, observe the Fede...