Commercial jet air we breath

[pauldw]

The air you breath will always be 21% oxygen

Apparently you have not been in my bathroom.

 

[lowwall]

The air you breath will always be 21% oxygen

No it isn't. Cabin air is constantly recycled with 25-50% of the cabin volume's worth of outside air being added each minute. Excess air is vented off through an overpressure valve.

Since a sizable percentage of the cabin air is breathed each minute, the O2 and CO2 levels are somewhere between those of the outside air and exhaled breath.

There have been multiple studies measuring cabin CO2 levels in flight*. The average reading is right around 1%, with most readings falling between .4% and 2%. Compare that to .004% in fresh air and around 4% in exhaled air.

The additional CO2 has to come from a decrease in 02, so the average O2 percentage in an aircraft cabin is 20%, not 21%.

* for example, a survey of study findings is at https://cot.food.gov.uk/sites/default/files/2022-12/TOX-2022-65 Aircraft cabin air CO2 and CO.pdf

 

[NW Dive Dawg]

When flying, I personally have found that the percentage and quality of Vodka in my Bloody Mary is far more of a concern than the cabins atmospheric 02 content.

 

[Eastwest]

Rumdumb from Hippydum flew Jet Blue yesterday from LAX to PBI with oxygen analyzer in tow and what would you believe the oxygen was in stow . I may trust your comments more than this devise or your bad advise with my life . " Hint " Aspen Colorado 8000 ft high 10.9 PSI

 

[happy-diver]

Hey mate just open the window

 

[wnissen]

I have a $250 CO2 monitor (so not lab grade but perfectly serviceable for this task) and it consistently reads 1000-1500 parts per million on commercial aircraft. At least on 737, 787, 757, and A350. Compare that with a reading in the 400 ppm range for fresh air. So I am not particularly impressed with the amount of fresh air circulation. If I put my car on fresh air and the fan on halfway, I get much more fresh air than that. To be fair, indoor air in a building can easily be above 1000 ppm, and the OSHA action rate for industrial safety is 5000 ppm. So the airplane is still reasonable.