Safety and Emergency Equipment

33.1 Aircraft Oxygen Systems

• Required to protect occupants from hypoxia (oxygen deficiency) at high altitudes, either
• during normal flight in unpressurized aircraft or following a depressurization in pressurized
• aircraft.
•  Time of Useful Consciousness (TUC): The limited time a person has to take corrective
• action after an oxygen deprivation before losing consciousness. At 35,000 ft, this is only 30-
• 45 seconds.
•  System Types:
• Gaseous Oxygen: Oxygen is stored in high-pressure green cylinders.
• Chemical Oxygen Generators: Commonly used for passenger oxygen. Pulling on the mask
• initiates a chemical reaction (Sodium Chlorate and Iron) that produces oxygen. Once started,
• it cannot be stopped and typically provides 15 minutes of oxygen.
•  Mask Types:
• Diluter-Demand (Crew): Supplies oxygen only when the user inhales. It mixes cabin air
• with pure oxygen at lower altitudes and supplies 100% oxygen above ~32,000 ft.
• Continuous Flow (Passengers): Supplies a constant flow of oxygen once activated.

33.2 Fire and Smoke Detection/Protection

•  Smoke Detectors: Located in cargo compartments and lavatories. They can be optical
• (photoelectric) types that detect light scattered by smoke particles, or ionization types that
• detect a change in air conductivity caused by smoke.

•  Fire Detectors: Located in engine nacelles and APU compartments. Modern systems use a
• continuous fire wire or gas-filled tube that loops around the fire zones and triggers an alarm
• when it is heated to a set temperature.
•  Fire Extinguishing:
• Fixed Systems: Fire bottles containing a halogenated hydrocarbon extinguishing agent (e.g.,
• Halon) are installed for the engines and APU. The pilot can discharge them from the cockpit
• after shutting down the affected engine.
• Hand-Held Extinguishers: Located in the cockpit and cabin for fighting internal fires.

33.3 Evacuation Systems

•  Emergency Lighting: An independent, battery-powered lighting system that illuminates exit
• signs, the cabin, and escape paths for at least 10 minutes.
•  Emergency Exits: Clearly marked doors and hatches. Over-wing exits and doors on large
• aircraft are equipped with inflatable escape slides which deploy automatically when the door
• is opened in the "armed" mode. Some slides can also be detached and used as life rafts.
•  Personal Flotation Equipment: Life jackets are provided for flights over water. They are
• inflated by a CO₂ cartridge or orally.