A lack of oxygen will kill you - and apparently too much oxygen can be deadly too.
New research shows giving too much oxygen to sick patients can do more harm than good.
The international study found that using oxygen liberally can increase the chance of death of a hospital patient by 21 percent.
Co-author Dr Paul Young says working out the perfect amount of oxygen will take time.
"One of the big challenges still is going to be implementation of this knowledge and changing practice in our hospitals both in New Zealand but also around the world," he says.
However he says some hospitals are already decreasing their oxygen use.
"As evidence accumulates, particularly if it concerns these findings, I think you'll find we become as concerned about high oxygen as we are about low oxygen," he says.