We like the performance, practicality and excellent build quality, but the price hammered its chances. It’s the same with a fridge. In some cases, the seal on a fridge door will be sufficient to keep the signal from the key in and any external signals out. In other cases, it won’t isolate the key sufficiently to be any use. Obviously it has to fulfil its primary purpose of isolating the signal from the key. Good ones are made from several layers of copper and plastic. But if you want to make your own, you could use aluminium kitchen foil and paper. We like the bag’s general build and tough feel, and it took either of our phones and a key with a little effort, but it wasn’t elegant.

Signal Blocking Pouch RFID - Phone Case Signal Defender Signal Blocking Pouch RFID - Phone Case Signal

We like the smart carbon fibre-effect construction and the extra front section, which was useful but wasn’t protected. We like the tough, high- quality feel of the bag’s textured polyester. It’s claimed to suit 99 per cent of key fobs and ours fitted, along with three credit cards that slotted into the protected front section.

All you need to know about Faraday boxes

Whenever you think your car key might be vulnerable to having its signal grabbed. Ironically, the easiest cars to steal using relay theft are those parked on people’s drives. The thief knows exactly where the keys for that car are: somewhere behind the front door. The bag must be fit for purpose too. Some people might want a Faraday bag that’s portable; some might want one that they can just leave in their house for when they’re at home. The latter might be able to get away with a less robust article.

AA Car Key Signal Blocker Wallet - WeeklyDeals4Less Pack of 2 AA Car Key Signal Blocker Wallet - WeeklyDeals4Less

Relay theft has been around for a couple of years now and car makers have got wise to crooks. Some car companies now make keys that don’t emit a signal unless they’re moving, or after they’ve been stationary for a short period of time. Other’s make keys that can be turned off if they’re not needed. Although manufacturers are taking steps to make keyless-entry vehicles more secure, many models remain vulnerable to technically adept thieves. We are also impressed by the two-year replacement guarantee, which shows Halfords’ confidence in the product. A poor-quality Faraday bag may stop working because it has failed and can no longer prevent the signal from escaping.

\n\t\t\tHalfords Anti-Theft Car Key Signal Blocker - Black

It makes sense to always use a Faraday bag when the car is on your driveway or in a garage, but also when you’re away from home, because thieves often operate in car parks. Uniquely, it doesn’t use Velcro to close the bag, but two pop studs that make for a secure fastening. It worked well with the remote keys, but has no separate compartment. Just as they don’t allow the signal to escape, neither do these bags allow any signal to enter. So once in a Faraday bag, your car key will neither transmit nor receive. Do Faraday bags work for car keys?

Car Key Signal Blocker Pouch with Hook Securing Keyring Car Key Signal Blocker Pouch with Hook Securing Keyring

At a push we squeezed in a key and a phone, but the Velcro section along the flap wasn’t full width and protection was a bit hit and miss as a result. Some people might want one to put their mobile phone in; some might want them for their car keys. It’s worth remembering that car keys can differ dramatically in size nowadays too. Do you need a Faraday box for car keys?It took our key and two credit cards, but isn’t particularly big – just a little larger than the Halfords and Olixar. The strong Velcro flap makes it unlikely any stray signals could get in and, in the test, none did. This kind of crime is referred to as ‘keyless theft’ or ‘relay theft’ because of the way the signal is relayed. The whole process can take a team who know what they’re doing less than a minute. How do Faraday pouches work?

Streetwize Car Key Signal Blocking Pouch Black, Double Pack

Bauer Consumer Media Ltd, Company number 01176085; Bauer Radio Limited, Company number: 1394141; Registered office: Media House, Peterborough Business Park, Lynch Wood, Peterborough PE2 6EA and H Bauer Publishing, Company number: LP003328; Registered office: The Lantern, 75 Hampstead Road, London NW1 2PL Put your key in the sandwich bag then wrap that in aluminium foil, carefully sealing three edges. Make sure you can still access the sandwich bag’s opening (the fourth edge that you don’t seal). To see how good the item really is, put your mobile phone in it (assuming it fits). Then ring your phone. A fully functioning Faraday bag should prevent the signal getting through to your phone. What makes a good Faraday pouch?The aim of a Faraday pouch is to contain the signal transmitted from a car’s key. To do this, the bag must be lined with something that doesn’t allow the signal to escape. This is usually metallic and frequently involves a number of layers to ensure the signal is well and truly contained. The Velcro strip extends completely across the bag, which should seal it completely, but although it worked well with the remote key, it failed to prevent both the Bluetooth and WiFi signals getting in, which is a shame. In some cases, biscuit tins will work as a Faraday bag; in other cases not. Put your keys in a biscuit tin and if it has a tight-fitting lid, it should prevent signal getting through. If the signals are very strong, it might not.