Lithium batteries currently exist in almost all portable electronic devices including phones, tablets,
laptops, headphones, power banks, watches, portable media players, e-readers, e-cigarettes and smart bags.
Crew members are also carrying electronic flight bags and manuals and point of service devices in addition to their portable devices.
Lithium batteries are capable of overheating, leading to a process called thermal runaway, which can cause the sudden
release of the contents of the battery as heavy smoke, flammable gasses, flames, or in some cases the battery can explode.
Once one cell in a battery pack goes into thermal runaway, it produces enough heat to cause adjacent cells to go into thermal runaway.
The resulting fire can flare repeatedly as each cell ruptures and releases its contents.
Here, for example, is a five cell battery in which the first cell experiences thermal runaway and burns out.
But the battery isn't finished burning; two or three minutes later
the heat propagated from the first cell causes the adjacent cell to flare up.
This process repeats every two or three minutes until all five cells are consumed.
In this clip you see a laptop on the left, a tablet in the middle and a mobile phone on the right.
This video demonstrates the difference in the reactions of the three devices with three different batteries.
When portable electronic devices overheat in thermal runaway there is typically a prolonged and larger reaction
in a larger device like a laptop and a shorter and less violent reaction in a smaller device like a mobile phone.
Larger batteries like those in laptops may have more cells which is why there is more opportunity for propagation meaning the fire could last longer.
Notice how the tablet and mobile phone have finished flaming while the laptop on the
left starts another thermal runaway and flames erupt again as the cells propagate.
Depending on how the lithium battery in the device is constructed, it may create more or less smoke or flames.
In general, the larger the device is, the larger the battery, and the greater the hazard.
Some of the first warning signs of an electronic device overheating and heading
towards thermal runaway are any of the following: slight bulging, a discoloration of the screen
an unusual odor or unusually hot to the touch.
When an overheating device is identified, the hazard to the aircraft is significantly reduced if the device is immediately removed from the flight deck.
The aircraft floor is a good location for easy access to fight the fire as well as decreased fire spread.
There are basic lithium battery firefighting principles that always apply even if the device is not removed from the flight deck.
First: Immediate, aggressive action is key.
Second: The onboard fire extinguisher should be used to remove any flames.
Finally, the third key principle is cooling.
Cooling can be accomplished by dousing the device with water or other non-alcoholic liquids, such as beverages.
Cooling should continue until the device has reached cabin temperature again.
This may take a few seconds or a few minutes partially depending
on how well the liquid or non-alcoholic beverage is applied.
When in doubt, apply extra.
The purpose of using the liquid is to cool the batteries.
To be more effective, direct the liquid into available openings in the device so that the liquid can reach internally to the batteries.
This will end the event sooner and decrease the likelihood of propagation.
Cooling is especially important in larger devices where you are trying to prevent
the thermal runaway from propagating to the rest of the device or surrounding area.
If the flames are not extinguished or the device is not properly cooled, flames and fire could continue to spread.
This may lead to a catastrophic event or dense accumulation of smoke in the aircraft.
Once the hazard is eliminated, the aircraft ventilation system will cause the smoke to dissipate.
There are several potential hazards that should be taken into consideration for a thermal runaway event.
A battery fire is intensified when aircraft oxygen gets involved in the fire.
This scenario can quickly make a small battery fire into an uncontrolled event.
When cooling the device, caution should be exercised to not use excessive liquids that may compromise aircraft electronics.
Smoke may be generated at a rate and quantity in the flight deck to the point that flight instruments may be obscured.
This further supports the need for immediate and aggressive action.
When an overheating device is removed from the flight deck it is important to coordinate with cabin crew who will be further responding to the hazard.
Once the device has cooled sufficiently, the safest place for it to be stored is completely submerged in liquid.
Battery technology and the hazards associated with overheated batteries is constantly evolving.
Being aware of the potential hazards of overheated electronic devices, and the most
effective techniques to mitigate them is important for ongoing operational safety.
Operators are encouraged to incorporate these principles into their training programs and procedures.