The only real problem with that is most dinosaurs lived in a time when there was 30% oxygen in the air. Maybe they could survive a bit at only 20%, but I imagin

The only real problem with that is most dinosaurs lived in a time when there was 30% oxygen in the air. Maybe they could survive a bit at only 20%, but I imagine it would be like someone living on the top of Everest and before long succumbing to the lack of oxygen.