Two lithium batteries ignited in this rucksack at Yeager Airport in West Virginia, USA. Two lithium batteries ignited in this rucksack at Yeager Airport in West Virginia, USA.

Lithium-ion batteries exploded in a passenger’s rucksack just moments before they were due to board an aircraft.

The passenger was going through a security checkpoint at Yeager Airport in Charleston, West Virginia, when the batteries attached to a charger caused a small explosion and fire.

The rucksack was quickly doused by Yeager Police and no-one was hurt in the drama … but it would have been a far trickier incident had the batteries ignited on board the plane at 30,000ft.

Lithium-ion batteries are used to power all personal electronic devices such as laptops and mobile phones. On an average plane there are thought to be at least 500 such devices brought on board by passengers.

Lithium-ion batteries are classed as dangerous goods when it comes to transporting them by air. This means they cannot be shipped in the cargo holds of passenger aircraft.

The fear is that if they catch fire they will go into what is known as thermal runaway and the cargo holds of planes are simply not designed to deal with such a fierce blaze.  The fires are often caused by faulty lithium-ion batteries inside electronic devices ranging from mobile phones to laptops carried on board by passengers. Crushed lithium-ion batteries have sparked huge fires at recycling centres.

During thermal runaway one cell overheating in a battery 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. Incidents of thermal runaway are on the rise.

It means passengers should always pack their lithium-ion batteries in bags they take into the aircraft cabin so if there is a problem the flight crew is trained to deal with it.

This means that spare lithium-ion batteries as well as external battery packs are prohibited in checked luggage along with e-cigs and vaporizers and should be kept with the passenger in the cabin. Spare batteries should be protected from short circuiting with terminal caps or tape and never put in pockets where they could come into contact with change, keys and other conductors, causing terminals to be bridged.

The rise in lithium battery fires is posing a particular problem in the confined space of passenger aircraft which is why cabin crew now often include in the safety briefing a warning that if passengers lose their mobile phones down seats they should alert the staff and not try to retrieve it themselves. If they do, the phone could get crushed in the seat mechanism, sparking a thermal runaway fire.

One way to tackle such incidents is to use an AvSax fire containment bag which can deal with fires in personal electronic devices and are now carried on more than 15,373 aircraft operated by 75 airline companies across the world – including some of the biggest and best-known.

AvSax  - which won the Queen’s Award for Enterprise in 2018 - has been used 30 times to deal with emergencies since the start of 2017. Deployment is so effective that extremely expensive diversions to alternate airports are avoided.