Ventilation

This regulation sets minimum air quality and ventilation standards for aircraft operating under Part 121 (scheduled air carriers).

Air Quality Requirements: All passenger and crew compartments must have adequate ventilation. Carbon monoxide levels cannot exceed 1 part per 20,000 parts of air (50 parts per million), and fuel fumes must not be present at all. These limits protect occupants from toxic exposure during flight.

Airflow Control: When compartments are separated by partitions with louvres or openings that allow air to pass between them, the crew must have a convenient way to shut off this airflow when needed. This allows the crew to isolate compartments in case of smoke, fumes, or other air quality issues in one area.

In practice, this means airline aircraft must have functioning ventilation systems and the crew must be able to control airflow between different sections of the cabin to maintain safety and air quality throughout the flight.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*