Airplane pilot flight performance on 21 maneuvers in a flight simulator under varying carbon dioxide concentrations.
Level 2 - randomized trial
Double-blind randomized crossover trial testing acute environmental exposures
PubMed 30089876 · doi:10.1038/s41370-018-0055-8
What was done
Thirty active commercial airline pilots completed three 3-hour flight segments in an FAA-approved flight simulator, each under a different CO2 concentration (700, 1500, and 2500 ppm) modified with ultra-pure CO2 while holding ventilation rates constant. Pilots performed predefined maneuvers of varying difficulty without autopilot, evaluated by an FAA Designated Pilot Examiner according to FAA Practical Test Standards. Both pilots and the examiner were blinded, and the order of exposure was randomized.
What was found
Compared to segments at 2500 ppm CO2, the odds of passing a maneuver were 1.52 times higher at 1500 ppm (95% CI: 1.02-2.25) and 1.69 times higher at 700 ppm (95% CI: 1.11-2.55), controlling for maneuver difficulty, examiner, and order of maneuvers.
Why it matters
This trial shows that elevated CO2 levels frequently encountered in aircraft cockpits and indoor spaces directly impair complex task performance independent of ventilation rates.
Limits
The study had a small sample size (30 pilots), was conducted in a flight simulator rather than real flight conditions, relied largely on subjective examiner ratings over purely objective telemetry, and only measured acute 3-hour exposures.
Cited by
- contradicts Adverse effects from indoor carbon dioxide levels primarily occur at concentrations of 2,000 to 3,000 parts per million, whereas levels around 1,200 to 1,300 ppm are common and generally not severely problematic.