We know the drill. Before our flight takes off, cabin crew gives us a run down of all the safety features of the plane. This covers emergency exits and safety protocol as well as an introduction about the oxygen masks. But where does the oxygen from those masks come from?
The masks on the airplane generate oxygen through a simple chemical reaction. The reaction is triggered when the masks are tugged by the passenger when they are dropped due to cabin depressurization.
Why Do We Need Extra Oxygen On-Flight?
The masks that drop down in-flight are actually there for your safety. When the airplane reaches high altitudes, the air thins up and the oxygen levels in the area starts to lessen. The aircraft is designed to keep the cabin pressure at an optimum level. When it does go below the standard level, the masks drop down to provide you with oxygen. (Source: Science ABC)
Is There an Oxygen Tank On-Board That is Directly Connected to the Mask?
The short answer to this is, no. Instead of having oxygen tanks on-board, the masks on the plane provides you with oxygen when a chemical reaction is triggered when they are tugged. The Oxygen Candle is ignited through a release of a firing pin, this allows the Sodium Chlorate and Potassium Perchlorate to combine to produce Oxygen that is safe for you to breathe in. (Source: Cabin Environmental Control Systems)
The reaction goes as such:
NaClO3 + BaO2 + KClO4 —> O2
Other oxygen candles use potassium and lithium chlorate, or sodium, potassium and lithium perchlorate. (Source: ACS Publications)
What is an Oxygen Candle?
The Oxygen Candle or also known as a chlorate candle is a cylindrical oxygen generator that contains chemicals that produces about 6.5 hours worth of oxygen per kilogram of the mixture. These candles have a prolonged shelf-life when they are stored properly. Some candles have been stored for over 20-years without a decreased output. (Source: Cabin Environmental Control Systems)
The technology of these candles are commonly used in the masks of aircrafts. They are also used by firefighters, submarine crew and mine rescue teams, basically everywhere compact emergency oxygen is required. (Source: Science ABC)
Do You Need to Wear the Oxygen Mask Until the Plane Lands?
The masks are not required to be worn throughout the flight. In fact, they can only provide oxygen for a short time. During this time the pilots work out a way to get the aircraft back to a safe zone where the altitude is within normal range.
The cabin crew usually announces when the plane has descended to a breathable part of the atmosphere and it is already safe to take your masks off. (Source: Science ABC)
At What Altitude Does the Oxygen Masks Drop?
We know that the masks are there to prevent us from getting hypoxia. Hypoxia is when there is a deficient amount of oxygen reaching your tissues and organs. The masks usually drop out of their compartment when the aircraft reaches 14,000 to 40,000 feet. (Source: CNBC)