The most reassuring thing about AEDs

AEDs are designed for ordinary people, not just trained medics. They give clear voice prompts. They analyze the heart rhythm and won’t deliver a shock unless the rhythm calls for one. They tell you exactly what to do at every step. Because that judgement is built into the device, the rescuer needs to make no diagnosis at all — which is precisely why the guidance is that an AED requires no training to use (ILCOR / ERC 2025).

What that means in practice: if you’re standing next to someone in cardiac arrest and there’s an AED nearby, use it as soon as it’s available. For every minute defibrillation is delayed, the chance of survival falls by roughly 7–10% (Canadian Red Cross 2025). Even with zero training, you’ll do better than not trying.

The 6 steps, in order

1. Confirm the casualty needs an AED

   Check responsiveness — shake the shoulders, shout “Are you okay?” Check for normal breathing — look at the chest for no more than 10 seconds. If the person is unresponsive AND not breathing normally (or only gasping), this is cardiac arrest. Call 911 immediately (or have someone else call), then have someone retrieve the AED while you start CPR. Every second matters.

2. Turn on the AED

   Open the lid or press the power button. The device immediately starts voice prompts. From this point on, the AED tells you what to do — listen and follow. You do not need any training to operate it.

3. Expose the chest

   Bare the casualty’s chest — remove or cut away the shirt. The pads need direct contact with bare, dry skin to work. Wipe the chest dry if it’s wet from sweat, rain, or water. Remove any medication patches (nicotine, nitroglycerin, hormone, etc.) and wipe the area clean. It is not always necessary to remove a bra — often you can simply move or adjust it so the pads sit on bare skin in the correct position (Canadian Red Cross / AHA / ILCOR 2025). Excessive chest hair only matters if the pads won’t stick — most AEDs include a razor in the kit. Place the lower pad on the ribs below the breast, avoiding breast tissue.

4. Attach the pads

   The pads have pictures showing where they go — follow them. Standard adult (anterior-lateral) placement: one pad on the upper right chest, just below the collarbone; the other on the left lower ribs, below the armpit at the mid-axillary line. Press firmly so they stick to bare skin. If a second rescuer is present, keep doing CPR while the pads are being attached. The pads are pre-gelled and disposable — pull off the backing as you place them.

5. Let the AED analyze

   The AED will say “stand clear” or “analyzing — do not touch the patient.” Step back. Make sure nobody is touching the casualty — contact blurs the AED’s reading of the rhythm and risks the current reaching a rescuer. The device is reading the heart rhythm and deciding whether a shock will help. This takes a few seconds.

6. Deliver the shock if advised, then resume CPR

   If the AED says “shock advised,” make sure nobody is touching the casualty, then press the shock button (fully-automatic AEDs deliver the shock themselves without a button; semi-automatic units need you to press it). The instant after the shock — or if “no shock advised” — immediately resume CPR: 30 compressions, 2 rescue breaths, repeat. The AED will re-analyze about every 2 minutes and tell you when to stop CPR for the next analysis. Keep going until paramedics arrive (Canadian Red Cross / Heart & Stroke, ILCOR 2025).

Source: Canadian Red Cross 2025; Heart & Stroke Foundation; ILCOR / ERC 2025 BLS (anterior-lateral pad placement; anyone can use an AED, no training required; continue CPR while pads attach; restart compressions immediately after a shock).

Using an AED on a child or a baby

The AED procedure is the same for a child (1 year to puberty) and a baby (under 1 year) as it is for an adult — do not withhold defibrillation because of age (Canadian Red Cross 2025). The specifics:

• Children and babies under about 25 kg (55 lb) — use pediatric pads if available, or the AED’s child key/switch. These deliver a lower-energy shock calibrated for smaller bodies.
• If pediatric pads or a child setting aren’t available, use adult pads — do not delay or skip defibrillation. Keep the pads at least 2.5 cm (1 inch) apart; if there isn’t room on the chest, use front-and-back (anterior-posterior) placement — one pad on the centre of the chest, one on the back.
• For a baby under 1 year, the AED is used the same way — use pediatric pads or the child key. Keep giving high-quality CPR while the AED is retrieved and applied; do not treat the AED as optional.
• Remove any medication patches before applying pads, and wipe the chest dry.
• The Chase McEachern Act protects users using AEDs on children and babies in good faith, just as it does for adults.

Source: Canadian Red Cross 2025 (AED procedure the same for child/baby; pediatric pads or child key for <55 lb; adult pads if none; pads ≥2.5 cm / 1 in apart or anterior-posterior; remove medication patches). See our baby CPR guide.

Special situations

Wet casualty or wet surface

Move the casualty to a dry area before applying the AED if at all possible. Wipe the chest dry. If you’re outdoors in rain, position yourself to minimize water on the casualty during shock delivery. Current takes the easiest path, so a wet chest can divert energy away from the heart.

Metal surface

Move the casualty off the metal if possible. If not, the AED will still work — the shock is delivered through the pads, and the risk of bystander shock through metal contact is minimal. Moving off metal is a reasonable precaution when it can be done quickly.

Pacemaker or ICD

You’ll see a small bump or scar under the skin (usually upper left chest). Place the AED pad at least 2.5 cm (1 inch) away from the device — don’t put the pad directly over it.

Pregnancy

Use the AED normally. The shock targets the heart, not the abdomen. Pregnant women in cardiac arrest need the same defibrillation as anyone else.

Hairy chest

If the pads won’t stick because of chest hair, most AED kits include a razor. Quick shave on the pad areas, then apply. Some kits allow a “rip and replace” approach — press on the first set of pads to remove hair when you tear them off, then apply a fresh set.

Jewelry

Remove necklaces or move them out of the pad area. Don’t waste time on small items like piercings — just place the pads around them, keeping about 2.5 cm (1 inch) of clearance.

What if the AED says “no shock advised”?

This doesn’t mean stop helping. It means the heart rhythm at that moment isn’t a shockable rhythm. Some cardiac arrest rhythms (asystole, pulseless electrical activity) don’t respond to defibrillation — but high-quality CPR keeps blood flowing until either a shockable rhythm returns or paramedics arrive with additional interventions.

Resume CPR immediately: 30 compressions, 2 rescue breaths, repeat. The AED will re-analyze about every 2 minutes. Keep going.

What if the AED makes a mistake?

It won’t shock someone who doesn’t need it. AEDs analyze the rhythm and only deliver a shock when a shockable rhythm (ventricular fibrillation or pulseless ventricular tachycardia) is present. If you place pads on someone with a normal heartbeat, the device will analyze the rhythm and say “no shock advised.” Because the device makes that decision, you cannot deliver a shock to someone who doesn’t need one — this is the safety feature that makes AEDs usable by any bystander (Canadian Red Cross 2025).

How CPR and AED work together

The chain of survival in cardiac arrest:

1. Recognize the event (unresponsive, not breathing normally)
2. Call 911
3. Start CPR immediately
4. Use the AED as soon as one is available
5. Paramedics arrive with advanced care

CPR keeps blood flowing to the brain and heart while the AED is being retrieved and applied. The AED then briefly stops the heart’s chaotic electrical activity so its own natural pacemaker can resume an organized rhythm. After the shock — or if no shock advised — CPR resumes immediately to keep blood flowing until the next analysis or until EMS takes over. Neither CPR nor AED alone is as effective as the combination (Canadian Red Cross 2025).

Training matters

The Chase McEachern Act protects untrained bystanders, and the AED’s voice prompts make it possible to use one with no training. But trained users respond faster, place pads correctly the first time, and integrate AED use smoothly with high-quality CPR. Standard CPR Level C, Standard First Aid, and BLS courses all include AED training as part of the curriculum — you don’t need a separate AED-specific course.