AED

How to Use an AED: A Step-by-Step Guide

An AED is designed for the public to use. It checks the heart's rhythm and tells you exactly what to do — you cannot accidentally shock someone who does not need it.

Published June 18, 2026 · Canada First Aid Training

Sudden cardiac arrest can happen to anyone, anywhere. An automated external defibrillator (AED) is a portable device that analyzes the heart's rhythm and, if needed, delivers a shock to help it return to a normal beat. Early CPR combined with early defibrillation gives a person the best chance of survival, which is why AEDs are placed in many public spaces.

If you think someone is in cardiac arrest, the most important actions are to call 9-1-1, start CPR, and use an AED as soon as one is available. Every minute counts.

Step by step

  1. Check for cardiac arrest. The person is unresponsive and not breathing normally.
  2. Call 9-1-1 and send someone to bring the nearest AED. If you are alone, put your phone on speaker.
  3. Start CPR. Push hard and fast in the centre of the chest while the AED is being retrieved.
  4. Turn on the AED as soon as it arrives and follow its voice and visual prompts — the device guides you through every step.
  5. Attach the pads to the person's bare, dry chest exactly as shown on the pad diagrams.
  6. Let the AED analyze. Make sure no one is touching the person while it checks the heart rhythm.
  7. Deliver a shock if advised. Confirm everyone is clear of the person, then press the shock button. If no shock is advised, the AED will tell you to continue CPR.
  8. Resume CPR immediately after the shock (or if no shock is advised) and keep following the AED prompts until emergency responders take over or the person shows signs of life.

Using an AED on a child or infant

For young children, use pediatric pads or a pediatric setting if the AED has them. If pediatric pads are not available, standard adult pads can be used — just make sure the two pads do not touch each other. Always follow the device's instructions.

A few safety reminders

  • Make sure the chest is dry; wipe it if necessary before attaching pads.
  • Move the person away from standing water before delivering a shock.
  • Do not place pads over a medication patch or an implanted device — place them at least a few centimetres to the side.
  • Keep interruptions to CPR as short as possible.

AEDs are designed so that an untrained bystander can use them, but hands-on training builds the confidence to act quickly under pressure. The Heart & Stroke Foundation of Canada sets the resuscitation guidelines that first aid courses follow.

Authoritative sources

This article is for general information only and is not a substitute for certified, hands-on CPR and AED training. In a real emergency, call 9-1-1 and follow the AED's prompts and the dispatcher's instructions.

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