There is a famous air travel myth claiming that "pilots get more fresh air than passengers".
(source: The pure cure, p.375)
I would like experts to either dispel or confirm this myth, that pilots receive "better air" with higher oxygen levels than passengers, who have to breathe more recirculated air.
Although at first glance it might sound absurd, but when you think about it, it would actually make sense, because:
The worst thing that can happen to passengers is that they get tired. Sure, that may be unpleasant (think of the stale air in a crowded room), but does not pose a health or security risk.
Pilots, on the other hand, need to be wide awake and perform to the top of their abilities, as errors can be fatal. So any negative outside influences on pilot performance needs to be eliminated. In particular, pilot fatigue significantly increases the risk of pilot error.
However "CO2 levels directly affect pilots’ flight performance" as was tested in a study on 30 active commercial airline pilots performing maneuvers under varying carbon dioxide concentrations:
Previous research led by Allen and colleagues found that, in office buildings, CO2 concentrations between 1000-2500 ppm – levels once thought to be benign – negatively impact the cognitive function of employees. For the new study, they wanted to determine if higher CO2 levels on the flight deck would impair a pilot’s ability to perform advanced maneuvers and manage emergency situations, such as a single-engine failure during takeoff. […] Average CO2 levels on the flight deck are less than 800 ppm. However, they have been measured as high as 2000 ppm on the flight deck and even higher in the cabin during the boarding process. […] The National Research Council has suggested that current standards for ventilation rates on flight decks may be inadequate.
On the flight deck […] the average CO2 concentrations are typically <1000 ppm, but the 95th percentile concentration can be as high as 1400 ppm, depending on airplane type.
Compared to segments at a CO2 concentration of 2500 ppm, the odds of passing a maneuver as rated by the Examiner in the simulator were 1.52 times higher when pilots were exposed to 1500 ppm and 1.69 times higher when exposed to 700 ppm.
In light of the above it would make sense to prioritize pilots over passengers when it comes to circulation of fresh air.
I will post the results of my research into this question as an answer below, but would welcome other answers presenting technical evidence and quoting citable references.
This is not the same question as Q57941.
Q57941 asks if there is airflow between cockpit and cabin (as opposed to be hermetically sealed).
Whereas this question asks if more fresh air from OUTSIDE flows into the cockpit than into the cabin. Also, it addresses a very famous airline myth, and as such it has a valuable purpose.