At what height is the limit where we can no longer breathe ?

Question: At what height is the limit where we can no longer breathe ?
- Keywords:
  environment
Asked by five43end to Jess on 17 Nov 2019.
- Jessica Franklin answered on 17 Nov 2019:
  
  The higher up in the atmosphere we go the less oxygen there is in the air, about 3000 meters it can get harder to breathe but above 8000 meters apparently we cannot breathe any more!

Question: At what height is the limit where we can no longer breathe ?