Faraday Bags – a solution for electronic shielding whilst Off Piste Skiing

If you are up to speed on avalanche safety, then you’ll know that it’s best practice to switch your phone off whilst off piste skiing, to prevent it from interfering with your avalanche transceiver.

However, we all like taking photos and videos of our ski adventures and most people now do this on their phone. Switching your phone off and carrying a separate camera is still definitely the best solution – as you get better photos and don’t risk running down the phone battery for calling a rescue. In reality though, 95% of people don’t own a separate camera and use their phone for taking photos and video, which presents a problem if you are trying to ski with the phone switched off – as it means you have to power the phone on and off between each shot, which takes much longer than powering up a regular camera.

There’s also a risk of accidentally leaving your phone switched on after taking a photo and a few people are tempted to disregard the safety instructions and leave their phone switched on ready for the next shot… It’s a thing that I look out for when guiding and I’ve come across quite a few switched on phones being pulled out of pockets part way through the day and given friendly reminders to please switch them off! It’s not always deliberate – phones can easily be left on by accident and I’m sure we’ve all done it once, whether we realised it or not.

There is a solution however, which allows you to keep your phone on for photography, whilst avoiding transceiver interference issues – so we’ve been testing this and have produced some recommendations.

Faraday Bags

In simple terms, a Faraday Bag (or Faraday Pouch – same thing) is a bag that’s made of a fabric containing lots of very thin metal wires. When you place your phone (or any other electronic device) into the bag, the ‘metal cage’ that now surrounds the phone, effectively isolates it from the outside world. This means that the phone has no reception and cannot pick up any wifi signals, gps or bluetooth – but importantly, it also blocks any electrical interference created by the phone from reaching the outside world. The phone can also no longer be hacked or tracked, which is why Faraday Bags are extensively used by the police, military and security services as well as in corporate settings, to protect sensitive information. You may have already come across Faraday bags as a solution to prevent modern car keys being hacked as well.

Placing your phone inside a Faraday Bag is therefore an effective way of electronically shielding it from the outside world and preventing it from causing interference with your avalanche transceiver. Using one allows you to keep your phone switched on and readily accessible for photography whilst skiing – you just need to carry it >20cm away from your transceiver the same as a metal object. For more information, please read our avalanche transceiver interference advice article for detailed advice on managing electronics whilst off piste skiing.

For Guides and others using electronics for navigation, a Faraday Bag also provides a safe ‘garage’ for such devices when they are not in use – ie so you can keep it warm in a pocket and ready for use etc.

Airplane Mode

You may come across people on forums saying ‘If I switch my phone to airplane mode, it won’t interfere with my avalanche transceiver’ – this is a common urban myth and it’s totally incorrect! It’s the phones’ touch screen that causes most interference with avalanche transceivers and the screen still functions in airplane mode… However, it is still a good idea to put your phone into airplane mode if you are using a Faraday Bag, as the battery will last 4-5 times longer when the phone is in airplane mode.

Battery Usage

Airplane mode is best, but if you place your phone in a Faraday Bag when it’s fully functioning and trying to connect to a network, then this won’t drain the battery prematurely (we’ve had several questions about this, so we’ve tested it!) The phone uses battery power at the same rate as if it’s left unused outside the bag (4% in 8 hours in the case of my own phone, which has a 5000mAh battery). The power management systems on phones can deal with this – after all, it’s the same as going out in the mountains for the day in an area without phone signal, which doesn’t suddenly totally drain your battery – or we’d all be stuffed!

Limitations

Please note that whilst your phone is in the Faraday Bag, it is totally isolated from the outside world and non of it’s communication or location functions will work until you take it out again (ie no phone signal, gps, bluetooth or wifi). Beware however – you will find numerous ‘radiation RFID shielding’ phone cases and similar products for sale online (see warnings below), which claim to provide electronic shielding whilst allowing your phone to function normally – these are not the same as a Faraday Bag and should not be used for transceiver interference protection, as they do not provide full electronic interference shielding.

What to buy

We’ve bought and tested a number of different Faraday Phone Bags – cheap and cheerful ones made in the far east (~£5) and a high quality Uk made model (~£26) that’s recommended by the police and security services. We found the cheap ones with only a single layer of shielding material were better than carrying an unshielded phone, but still left a significant reduction in transceiver range, whereas the high quality model which has two layers of shielding material and a better design provided full shielding and caused no reduction in transceiver range and function during our testing, so we recommend the following Faraday phone bag:

Disklabs Phone Shield (PS1) Faraday Bag

If you live in the UK, you can buy these online at the funfoneshop website here: Disklabs Phone Shield Faraday Bag. Disklabs make a wide range of different Faraday Bags – for smaller phones, their ID Shield 1 Bag is another good one to look at and it’s also available on the funfoneshop website (funfoneshop also sell via Amazon, so you can buy them there as well, but for slightly more).

If you live in the USA, you can buy Disklabs products at the Teel Technologies website here: Disklabs Faraday Bags USA. All of the products mentioned above are available to buy online.

These are Uk made and thoroughly tested to police and security service preferred specifications – so if you want to take photos on your phone whilst off piste skiing, then buy a Faraday Bag, switch your phone to airplane mode which will maximise the battery life and carry it >20cm from your transceiver whilst skiing.

If you live outside the Uk and cannot get hold of this particular model, then look for a similar high quality branded Faraday Phone Bag/Pouch that is tested and manufactured to police/security service specifications etc – ie we do not recommend any of the very cheap Faraday bags you can buy online, as these don’t come with independent quality or testing guarantees and may not provide full electronic shielding protection.

Warning – don’t buy RFID blocking phone cases…

As mentioned above, if you search online for ‘radiation blocking phone case’ or similar search terms, you will find hundreds of phone cases for sale that promise to shield you from harmful electromagnetic radiation whilst making calls and prevent your phone from being hacked, but at the same time allow your phone to function normally. If this all sounds too good to be true, then unfortunately it is – as numerous of these phone cases have been tested and found not to live up to the claims made by their manufacturers. For our purposes, they do not provide complete electronic interference shielding between your phone and an avalanche transceiver, so shouldn’t be used for this purpose – buy a good quality Faraday Bag\Pouch instead.

If you want a cheap but effective alternative, then you could go for the ‘shoplifter solution’ and wrap your phone up in tin foil – this might sound a bit Heath Robinson, but it forms an effective Faraday Cage which will shield your phone (it’s a trick used by shoplifters to evade security tags!)

In conclusion, if you want to find out more about how to manage consumer electronics in avalanche terrain, then we strongly recommend that you read our avalanche transceiver interference advice page, which offers comprehensive up to date advice on the subject.