Also, for multiple reasons, no one should fly without wearing a P95 or comparable or superior mask. You never know when smoke will hit. It is most critical during takeoff and landing, or if on the ground at a terminal. 3M 8577 is decent, with an essential bonus carbon layer. Place a disposable ASTM level 3 surgical mask on top too.
Note that an SpO2 finger meter can fail to recognize CO poisoning; it can be misleading with a false normal value of SpO2.