A Faraday pouch is designed to contain the signal transmitted from a car’s key. The aim of them is to prevent crooks using the relay theft technique to steal a car. But do Faraday pouches work? Read on to find out.

What is a Faraday pouch?

A Faraday pouch or bag (sometimes called RFID bag) is lined with a material, frequently copper based, that contains the RF signal transmitted by a car key. The material absorbs and redistributes electronic signals from the key, not allowing them to escape. It’s this signal that tells the car that the key is nearby and allows the car to be unlocked without pushing a button on the key fob.

Is unlocking a car with a key in a Faraday pouch wrong?

The whole point of a Faraday pouch is to prevent the electronics inside from transmitting their signals out. If you can press the key in the pouch and it unlocks the car, it proves that the pouch isn’t working. Buy another one and you should see the difference.

How to buy a Faraday pouch

With the increase in relay theft (where criminals grab the signal from a key in a house and bounce it to the car, fooling it into unlocking and starting), there’s no shortage of Faraday pouches for sale. You can spend pretty much anything on one, from a couple of quid to £100. But some are better than others.

Here’s how you test a Faraday pouch. Put your key in it, hold the key and pouch next to the locked car and press the buttons on the key inside the bag. Your car shouldn’t unlock.

Then unlock the car and get into it. Put the key back in the pouch, push the car’s start-stop button. The engine shouldn’t start.

Check the quality of the bag. For maximum protection you should use it every day. That means it’s going to lead quite a hard life. You want the material to be thick and the stitching to be strong.

Finally, think about what you’re going to be using the bag for. Do you want it to be portable so you can put your car key in it when you’re on the go? Or is it just to use when you’re at home? And do you just want it for your car keys? Many are big enough to put mobile phones in.

What do the experts say?

Car magazine Auto Express conducts regular product tests on things such as Faraday pouches. It rates the Defender Signal Blocker as the best. Good news is, it costs around £5 and it’s big enough to take a smartphone.

Next up, it rates the £28 Disklabs Faraday Bag KS1. It’s smaller than the Defender which makes it more portable. Auto Express also rates the Halfords Anti RFID Theft Wallet product highly. Available from stores, it costs just £10.