The airline industry is very aware of the potential dangers of lithium-ion batteries catching fire on passenger aircraft – but how do they deal with a fire emergency on board?
Passengers routinely take hundreds of personal electronic devices (PEDs) on board aircraft every day including mobile phones, laptops, iPads, vapes and even earphones.
All are powered by lithium batteries which can potentially overheat and catch fire. When this happens the battery goes into what’s known as thermal runaway and the heat is so intense it can even cause the device to explode.
This would send sharp debris flying around the passenger cabin, potentially causing severe injuries and even catastrophic damage to the aircraft.
So it’s vital that any overheating or smouldering PED is quickly put into a lithium fire thermal containment bag and the most widely used within the industry is AvSax which are now on board around 16,750 aircraft operated by more than 100 airline companies.
The way it works is that the overheating device is put in the bag and then a couple of litres of water is added. This causes the gelling polymer inside the bag to expand and close around the device, cooling it. The AvSax is made from military grade material so should it explode then the heat and debris will be confined within the bag.
Thermal runaway happens when one cell in a battery overheats it can produce enough heat – up to 900°C (1652°F) – to cause adjacent cells to overheat. This can cause a lithium battery fire to flare repeatedly and they are very difficult to put out which is why it must go into an AvSax as quickly as possible.
The AvSax – by far the world’s best-selling lithium battery fire mitigation bag - has been deployed in action 33 times on board aircraft since 2017 and on every occasion the aircraft was able to continue safely to its destination with no need to divert or make an emergency landing. Each diversion can cost airlines hundreds of thousands of dollars.
The reason AvSax are so effective and are the main choice for airlines is that these thermal containment bags are designed to continually cool the overheating battery using water poured into the bag.
This use of liquid is recommended by the Civil Aviation Authority (CAA) in the UK and many other fire containment bags don’t work this way.
In its guidance the CAA states: “Since the development of the International Civil Aviation Organization (ICAO) guidance on dealing with an in-flight battery fire, new products designed for use in response to lithium battery thermal runaway events have become available.
“Products which provide both a cooling and containment capability are typically more aligned to the existing ICAO guidance as when used they are filled with water or other non-flammable liquid to act as a cooling agent.
“After knocking down flames it could conceivably take just a couple of seconds for a personal electronic device to be placed inside a containment bag, allowing it to be moved to a place of safety. Passengers could then return to their seats, mitigating potential unrelated safety hazards such as injury in the case of severe turbulence. Equally, the effect on flight crew in carrying out their duties following an event on the flight deck would be minimised.”
AvSax were devised by Environmental Defence Systems Ltd based in Huddersfield, West Yorkshire and the company won the Queen’s Award for Enterprise for their innovation in the UK – the top accolade any business can get.
Managing director Richard Bailey said: “It may seem strange to use water to stifle a fire in an electronic device but the water is mainly absorbed into the sides of the bag which then expand.
“Lithium battery fires are notoriously difficult to put out as we have seen on a larger scale with batteries used to power electric cars. They don’t need oxygen to keep flaring up so can reignite quite some time after they initially caught fire. The only way to effectively deal with it is to cool them down which is exactly what the AvSax is designed to do.”
If you want to read more about lithium battery fires on board aircraft our blog is probably the most comprehensive one in the world.
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