How to Use an AED Machine: A Step-by-Step Guide for Beginners

An automated external defibrillator (AED) is a portable device that checks the heart's rhythm and, when needed, delivers an electric shock to restore a normal beat. This guide shows you how to use an AED machine on an adult in sudden cardiac arrest, then covers what changes for children and unusual situations. Sudden cardiac arrest is an electrical malfunction that stops the heart from pumping effectively. It is not the same as a heart attack, which is a blockage of blood flow, though a heart attack can trigger arrest.

You need no prior training and no special permission to follow these steps. AEDs are built for laypeople and talk you through the process. What you do need is willingness to act. A hands-on CPR and AED course makes the sequence feel automatic when your adrenaline is high.

Step 1: Confirm Cardiac Arrest and Call 911

Before you approach, take two seconds to check the scene. Look for traffic, water, exposed wiring, fire, or anything else that could hurt you. You cannot help anyone if you become a second patient.

Then look for the two signs that matter:

Unresponsive: tap the person's shoulders firmly and shout, "Are you okay?" No response means unresponsive.

Not breathing, or only gasping: watch the chest for no more than about 10 seconds.

Pay special attention to gasping. Agonal breathing is a slow, irregular, snoring or gulping pattern that can occur in the first minutes of cardiac arrest. It is not normal breathing, and it is a common reason bystanders hesitate. If the person is unresponsive and only gasping, treat it as cardiac arrest.

Now get help moving. Call 911, or point at a specific person and say, "You, call 911 and bring the nearest AED." Naming one person works far better than shouting a general request. If you are using your own phone, put it on speakerphone and set it beside you so the dispatcher can coach you through compressions while your hands stay busy.

Step 2: Start Chest Compressions While the AED Is Retrieved

Compressions keep blood moving to the brain and heart until the AED is ready. Do not wait for the device before you begin.

Kneel beside the person, who should be on a firm, flat surface.

Place the heel of one hand on the center of the chest, on the lower half of the breastbone.

Put your other hand on top and lock your elbows, with your shoulders directly over your hands.

Push straight down about 2 inches (5 cm) for an adult.

Release fully and let the chest recoil before the next push.

Keep a rate of 100 to 120 compressions per minute.

That rate is consistent with current American Heart Association (AHA) and American Red Cross guidance. A useful way to find the tempo is the beat of "Stayin' Alive," though the dispatcher may also count for you.

Push hard and fast, and keep interruptions short. Every pause in compressions lowers the odds that a shock will work, so do not stop until the AED is open and ready to analyze. Compressions are tiring, and quality fades quickly, which is why a second rescuer matters later.

If you are alone, the decision depends on distance. When an AED is in sight, such as on the wall of the same room, get it and bring it back. If you cannot see one, stay and start compressions, and follow the dispatcher's instructions.

Step 3: Turn On the AED and Follow Its Voice Prompts

When the AED arrives, place it next to the person's head, on the side where you are working if possible. Turn it on. Many models start when you open the lid, while others have a green power button you press. Either way, the device will begin speaking.

Listen to it rather than guessing. The voice prompts walk you through each action in order, usually telling you to expose the chest, apply pads, and stand clear. Some units also show text or diagrams on a screen. Follow the prompts at the pace they give them.

Models differ in small ways. As of 2026, button placement, how the pad cable connects, whether there is a screen, and whether there is a child mode or key all vary by manufacturer. That is why a quick familiarization is worth it. If your workplace or home has an AED, open it once, look at the pads and the prompts, and you will not be surprised later. If you meet an unfamiliar model in an emergency, trust that model's own instructions over any general guide, including this one.

One of the most common fears is doing something wrong and hurting the person. The AED is designed to prevent that. It analyzes the heart rhythm and advises a shock only when it detects a shockable rhythm, an abnormal rhythm such as ventricular fibrillation that a shock can correct. If the rhythm is not shockable, the machine will not let a shock go through. Keep your compressions going until you are told to stop, and let the device do the deciding.

Step 4: Expose the Chest and Place the Pads Correctly

The pads must touch bare, dry skin to work. If a second person is present, one of you can keep up compressions while the other prepares the chest.

Prepare the skin

Remove or cut away clothing. Many kits include trauma shears for this.

Remove bras with metal underwires, since metal can interfere with the pads.

Dry the chest with a towel or shirt if it is wet or sweaty.

If the chest is very hairy and a razor is in the kit, quickly shave the spots where pads will go. Otherwise, press the pads on firmly, and if they will not stick, replace them with the spare set if available.

Position the pads

For an adult, the standard placement is:

One pad on the upper right chest, just below the collarbone.

The other pad on the left side of the chest, a few inches below the armpit, along the ribs.

Every pad has a diagram printed on it, so follow the picture if you are unsure. Peel the backing off just before you apply each pad, then press down from one edge to the other so there are no air pockets. If the AED prompts you to plug in the connector, push it firmly into the port, usually marked with a flashing light or a picture.

Do not let the pads overlap or touch each other. If you are placing them correctly, they will be well separated across the chest.

Step 5: Let the AED Analyze, Clear the Person, and Deliver the Shock

Once the pads are attached, the AED will say it is analyzing the heart rhythm. Stop touching the person at this point. Movement, including compressions, can disrupt the reading and delay or confuse the result. If the person is being moved in a vehicle or carried, stop that too until the analysis is complete.

The AED will then give one of two results.

If a shock is advised

Make sure nobody is in contact with the person. Say loudly, "Clear!" or "Everybody stand back!" and look to confirm that no one is touching them, including you. Check hands, knees, and anyone leaning in. Then press the flashing shock button. Some AEDs are fully automatic and deliver the shock after a countdown without any button press, so follow the prompts for your model.

If no shock is advised

This does not mean the person is fine. It means the heart is not in a rhythm that a shock can fix, and the person still needs CPR. Resume compressions right away and keep the pads on. The AED will analyze again in about two minutes.

The shock itself may cause the person's body to twitch or jerk. That is a normal response to the electrical current, and it is not a sign they have woken up or that you did something wrong.

Step 6: Resume CPR Immediately and Continue Until Help Arrives

Whether or not a shock was delivered, restart chest compressions as soon as the AED tells you to. Do not stop to check for a pulse or to see if the shock worked. Even after a successful shock, the heart often needs a few minutes of compressions before it pumps effectively on its own.

Leave the pads on the chest and keep the AED powered on. About every 2 minutes, the device will prompt you to pause so it can re-analyze the rhythm. Repeat the same cycle: hands off, clear, shock if advised, and straight back to compressions.

If another person is available, switch roles about every 2 minutes, ideally during the AED's analysis pause so you lose no time. Compression quality drops noticeably with fatigue, often before the rescuer realizes it.

Keep going until one of the following happens:

The person clearly begins breathing normally or moves purposefully.

Emergency medical services (EMS) arrive and take over.

The AED prompts you to do otherwise.

The scene becomes unsafe.

When EMS arrives, leave the AED attached and give the crew a short report: when the person collapsed, how many shocks were delivered, and how long CPR has been going. They will take it from there. Many AEDs record the event, and responders may need the device for that data.

Step 7: Adapt for Children, Infants, and Special Situations

Children

For children under about 8 years old or under roughly 55 pounds, use pediatric pads or a pediatric key or mode if the AED has one. These deliver a lower energy dose. If no pediatric option is available, use adult pads rather than delay, since a shock from adult pads is better than none. Because cutoffs and recommendations can be updated, confirm the current figures with the American Red Cross and AHA, which Taylored Instruction teaches in its courses. On a small child, the pads may be too close together on the chest, so place one on the front and one on the back, as the pad diagram shows.

Wet conditions and medical devices

Water: move the person out of standing water and dry the chest before applying pads. A wet surface alone, like a damp deck, is not a problem once the chest is dry.

Medication patches: if a patch sits where a pad goes, remove it and wipe the skin clean first.

Pacemakers or implanted defibrillators: you may see or feel a hard lump under the skin of the upper chest. Place the pad at least about 1 inch away from it, and do not delay the shock.

Keeping an AED ready

A device only helps if it works when needed. Check the status indicator regularly, which is usually a light or symbol showing the unit is ready. Note the expiration dates on the pads and the battery, and replace them on schedule. Taylored Instruction offers AED sales along with hands-on training, so you can equip a space and learn to use the device in one place.

Know Where Your AED Is Before You Need It

The best time to find an AED is when nothing is wrong. Walk through your workplace, gym, school, or apartment building and note where the devices are mounted. Check that each status indicator shows ready, and look at the pad and battery dates. If you coordinate safety for an organization, make sure staff know the locations too.

Reading the steps helps, but practicing them is what builds confidence. Courses taught through Taylored Instruction cover CPR and AED use under both American Red Cross and AHA programs, with personalized instruction at locations in the Vancouver, WA and Portland area and in San Luis Obispo, CA.

Don't wait until an emergency happens. Get the life-saving certification you need today. Register for a CPR, First Aid, or Lifeguarding class and gain the confidence and skills to respond when it matters most.