Deadliest gas on the world?

[Robby]

You know why I think that Oxygen is deadly?

Because, it feeds flames. When we inhale Oxygen, we exhale Carbon Dioxide. Certain processes take place in the body during that period. If the oxygen's concentration would be higher, we'd ignite from the inside!

Of course, if its concentration is also lower, we might suffocate.

This is one of those "you can't live without it, but can't continue living with it" cases.