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What is an automated external defibrillator (AED)?

An Automated External Defibrillator (AED) is a portable life saving device that can give a casualty’s heart an electric shock, when it has stopped beating normally in a sudden cardiac arrest.

A defibrillator works by checking the casualty's heart rhythm once the defibrillator pads are placed on their chest and giving them a shock if needed.

By using a defibrillator before an ambulance arrives, you can significantly increase someone’s chance of survival.

Browse our comprehensive range of semi and fully automatic defibrillators for schools and workplaces, with additional accessories to help you install and maintain your defibrillator.

What you should consider when purchasing a defibrillator?

  • who will likely need the defibrillator – in some cases children will need separate paediatric defibrillation pads
  • storing your defibrillator – fixed-location defibrillators should be stored in a cabinet or wall bracket, with appropriate signage
  • training – while you do not need to be trained to use a defibrillator, taking training can ensure you are familiar with the device and ready to act quickly in an emergency. Vitally, rescuers will still need to perform CPR, so it is important to know how to do this
  • educating your community – ensure your colleagues or community members are aware of the defibrillator, its location, how to access it, and how to use it.

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How much is a defibrillator?

Should a defibrillator be kept in a locked cabinet?

Different ambulance trusts recommend different things when it comes to locking the cabinet. Please check with the ambulance trust in your local area for their advice.

Some defibrillator cabinets are alarmed rather than locked, letting people know that the defibrillator is being accessed.

St John Ambulance believes defibrillators should made as accessible as possible to ensure they can be accessed quickly in an emergency.

Do defibrillators need to be registered with the ambulance service?

We've partnered with the British Heart Foundation, Resuscitation Council UK and UK Ambulance Services to make defibrillators more accessible via The Circuit and give them the best chance of saving a life.

The Circuit

Early defibrillation before emergency services arrive can help double a person’s chances of surviving an out-of-hospital cardiac arrest. However in the UK, defibrillation is received in less than 1 out of 10 cases. There are an estimated 100,000 defibrillators in the UK, but only 30% of defibrillators are known to ambulance services, which means that tens of thousands of defibrillators aren't used in an emergency because emergency services don’t know where they are.

The Circuit is the national defibrillator network which maps defibrillators across the UK, connecting them directly and automatically to each ambulance service.

Register on The Circuit to give your defibrillator its best chance of saving a life - put your defibrillator on the map.

Register on your defibrillator

Find out more about The Circuit and answers to some frequently asked questions, read our page.

What else to keep with a defibrillator

You will also need:

  • A towel, tissues, or wipes to dry the casualty’s chest if it is wet or sweaty.
  • A razor to shave the casualty’s chest.
  • Scissors to cut away the casualty’s clothing.
  • A face shield for administering CPR.

For more information on why you may need these items as a rescuer, read our Defibrillator guide for rescuers.

Did you find this information helpful?

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Defibrillators, accessories and training models

Explore our range of fully and semi-automatic defibrillators and everything you need to help you install and maintain your device.

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Free resources

Download our free defibrillator maintenance posters.

Defibrillator checklist

defibrillator checklist

Use our defibrillator maintenance checklist to keep track of your inspections and your pad and battery expiry dates.

Defibrillator location poster

defibrillator location poster

Use our defibrillator location poster to update signs around your workplace so everyone knows where their nearest def...

Book Defibrillator and CPR training

Defibrillator and CPR training

Learn how to operate a defibrillator and how to perform effective CPR to give you the confidence to act quickly and effectively if someone has a cardiac arrest.

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Related advice

Defibrillators - a guide for rescuers

Read our guide to understand what a defibrillator is, when you should use one, and who can use a defibrillator.

Guide to defibrillator maintenance and upkeep

If you are responsible for the upkeep of a defibrillator in your workplace or community, read our guide for answers to frequently asked questions.

How to use a defibrillator

By using a defibrillator before an ambulance arrives, you can significantly increase someone’s chance of survival. Learn what to do.