Considering that the two worst things that can happen on a passenger jet are a fire or a structural failure, fire detection and extinguishing are significant parts of airplane design and emergency equipment.
There are fire detection systems in the engine and APU compartments, as well as in the cargo bins and various locations in the cabin (think of the lavs). There are also overheat detectors in the wheel wells, but generally with no extinguishing capability.
There are also extinguishers on board. There is always a fire extinguisher in or near the flight deck for the crew. The cabin is also equipped with multiple extinguishers based on the number of people the plane can seat.
Two types of extinguishers generally are carried on board. The red canister that you might have in your home or see in your place of work or school is one of them, and it is equipped with Halon. Halon is the preferred option if the fire is electrical in nature, and it works by smothering the flame and depriving it of oxygen as quickly as possible. Because it is also compressed gas, it is cold, which helps to cool the temperature quickly around the source of the flame. The risk for the user is that, in a confined area, a chemical extinguisher may displace the oxygen you are breathing.
Water fire extinguishers are less prevalent, but they are only used for what are termed as Class A fires, such as paper or waste. For this reason, you can expect to see a water extinguisher near lavatories and/or galleys. Water might be able to put out a small electrical fire, but it also increases the risk of shock or electrocution, and considering that you might already be dealing with a compromised system, adding more risk to the equation doesn’t make sense.
In the age of rechargeable batteries used in phones, computers and tablets, fire awareness and extinguishing are even more important. There have been a number of onboard fires related to lithium batteries, and at least one cargo plane was lost to such a fire.
These fires burn extremely hot and are difficult, if not impossible, to control. As a result, airlines require that they be handled a certain way, and if a fire breaks out in a cabin because of a faulty battery, it is common to see some kind of thermal containment bag that is used to corral the offending device. The bag usually has a pair of heat-resistant gloves (think of a large oven mitt) that can be used to get the device in the bag. Once it is sealed inside, the hope is that the fire will burn out from a lack of oxygen. If a battery fire can be extinguished, it’s OK to douse it with liquids in order to smother it and get the temperature under control. In fact, it’s critical to keep an eye on the source, since the fire could reignite.
Fires are less of a threat than they used to be, which means when they do happen, they can totally catch everyone off guard. Learn what you can use to extinguish each type of fire, and know where the extinguishers are located and how to use them. Pay attention during training drills, and always be ready to put that training to use.—Chip Wright