Containment bags used to tackle burning electronic devices on planes must be able to have liquid in them.

This vital formal notice has been sent to airlines by the Federal Aviation Administration (FAA) in the USA after several containment bags have appeared on the market that don’t use water.

One bag now in use with several major airlines is the AvSax which DOES work with liquid and has been successfully used in action many times so far this year to cool down potentially dangerous devices ranging from mobile phones to iPads.

The formal advice from the FAA states: “Once the fire is extinguished, containment devices can be used to secure the portable electronic device. Keeping an unstable device cool is critical. In order to do so, any such containment device should be capable of holding liquid so that the device can be submerged during storage.”

If an electronic device starts to seriously overheat or emit smoke the cabin crew will pour at least two litres of water into an AvSax and then drop the device into the bag, adding additional water as required. The water activates the polymer gel inside the bag causing it to expand around the device. Should the device keep on venting then the AvSax is tough enough to absorb the force.

The AvSax cools the batteries in the device, reducing the likelihood of the battery catching fire but if it does go into what is known as thermal runaway when all the battery cells catch fire at incredibly hot temperatures it is all contained within the bag.

Amazingly, the water is absorbed into the internal lining of the bag so the device is dry when it is removed.