Auxiliary Power Unit (APU)

—A turbine engine that is used to power electric generators and provide bleed air for pneumatic and environmental control system use. The APU is normally used during ground operations when the main engines are not operating or are not operating at conditions which allow them to fulfill these needs.


—FAA’s Airworthiness Directive.


—Gases, such as CO2 in exhaled breath, human body odors, and volatile compounds produced by fungal and bacterial growth, released by humans, animals, microorganisms, or plants.

Bleed air

—Compressed air extracted from the compressor section of a turbine engine.


—Building Research Establishment.


—Building Related Symptoms.


—The section of an aircraft occupied by passengers.

Cabin crew

—The flight attendants who are responsible for the safety and comfort of the passengers. Because the majority of exposure and health-effects data has been collected in the cabin and might not be applicable to the cockpit, this report focuses on the cabin crew except where data are explicitly applicable to the cockpit crew. However, many issues that are pertinent to the cabin crew are relevant to the cockpit crew.

Cabin pressure altitude

—The distance above sea level at which the atmosphere exerts the same pressure as the actual pressure in the aircraft cabin. Cabin pressure altitude is the static pressure measured within the pressurized fuselage (i.e., cockpit and cabin) that represents the equivalent absolute ambient static pressure at a given altitude for a specific standard day or reference day conditions. The cabin pressure altitude is governed by the pressure schedule as set by the airplane manufacturer. Typical commercial transport airplane pressure schedules top out at a pressure of 10.92 pounds per square inch, which is equivalent to an altitude of 8,000 feet at U.S. standard atmospheric conditions.


—A person who harbors a specific infectious agent without visible symptoms of the disease; a carrier acts as a potential source of infection to others.


—Centers for Disease Control and Prevention.


—Code of Federal Regulations.


—Air movement within the aircraft cabin.


—Carbon monoxide.

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