What is the DEA's limit for oxygen in a breathing gas for aviation?

The correct answer is based on regulations from the Federal Aviation Administration (FAA) and the associated guidelines from the Drug Enforcement Administration (DEA). The DEA allows a maximum of 23.5% oxygen content in breathing gases used for aviation.

This limit is set to ensure the safety of pilots and passengers while maintaining the necessary physiological functions required during flight. Oxygen concentrations higher than this can lead to an increased risk of fire and toxicity, particularly in the pressurized environments found in aircraft.

In aviation, maintaining a careful balance of oxygen levels is crucial, as excessive oxygen can create hazardous conditions while still needing to provide sufficient oxygen for physiological needs. Hence, 23.5% is regarded as the safe upper limit for the use of enriched air in aviation contexts.