A blood oxygen level of 80 percent is getting dangerously low and you need oxygen to survive.
Your normal and healthy arterial oxygen level should be at approximately 75 to 100 millimeters of mercury (mm Hg).
If your blood oxygen level drops below that level of 75 to 100 millimeters of mercury then you need some supplemental oxygen to bring your blood oxygen levels back to correct and healthy levels.
Some people will have a blood oxygen level of between 95–100 percent which is also normal and if your blood oxygen level falls below that to 90 or 80 percent then it gets dangerously low.