When someone collapses, every second can feel like an eternity. But you don't need to be a doctor to be a hero. To use an AED device effectively, you first have to recognize the emergency, check for responsiveness, and call for help. The key signs are a sudden collapse, no response when you shake and shout, and abnormal or no breathing—this is your signal to act immediately.

Recognizing The Emergency And Taking Initial Action

In a moment of chaos, clarity is your greatest asset. Before you even think about grabbing an AED, you need to correctly identify the crisis as it unfolds. This isn't about making a complex medical diagnosis; it's about spotting clear, undeniable signs that someone needs help right now.

The event you're looking for is Sudden Cardiac Arrest (SCA). Unlike a heart attack, where the person is often conscious and breathing, SCA is an electrical problem. The heart abruptly stops beating correctly, and that leads to a few tell-tale signs anyone can spot.

Identifying the Signs of Sudden Cardiac Arrest

Look for this distinct trio of symptoms. If you see them, it's time to spring into action.

• Sudden Collapse: The person unexpectedly falls and is completely limp.
• Unresponsiveness: They won't respond when you tap their shoulders and shout, "Are you okay?"
• Abnormal or No Breathing: The person may be taking gasping, snorting, or gurgling breaths, known as agonal breathing. These are not signs of recovery. They may also not be breathing at all.

If you encounter this situation, do not hesitate. This is a true medical emergency where every passing moment is critical. Knowing how to react is often part of comprehensive workplace safety procedures that prepare teams for all kinds of emergencies.

The single most important thing to remember is that a person in Sudden Cardiac Arrest needs intervention now. Hesitation is the enemy. Your quick action is the bridge between their collapse and the arrival of professional medical help.

Your Immediate Action Plan

Once you've identified the signs, your next steps are simple but incredibly powerful. Your goal is to get professional help on the way and an AED to the scene as fast as humanly possible.

First, always make sure the scene is safe for you to approach. Quickly check for immediate dangers like traffic, fire, or electrical hazards.

Once it's safe, here is your quick reference guide to those first critical actions.

Initial Response Checklist for Sudden Cardiac Arrest

Being direct and specific with your commands is key. It cuts through the confusion and avoids the "bystander effect" where everyone assumes someone else will act. If you're all alone, call 911 yourself before doing anything else—put your phone on speaker so you can start CPR while talking to the dispatcher.

The urgency here can't be overstated. Statistics show that for every minute defibrillation is delayed, the chance of survival from cardiac arrest drops by about 7-10%. Recognizing the symptoms of SCA is the first domino to fall in a sequence that saves lives. You can learn more by reading our detailed guide on what is sudden cardiac arrest. This stark reality has driven the incredible advancements in AED technology we see today.

Preparing the Person and Powering On the AED

Alright, you've got the AED. This is where you shift from reacting to the emergency to taking focused, life-saving action. It’s totally normal to feel a surge of adrenaline, but the good news is that these devices are designed to be your calm, steady partner through this whole process.

Your very first move is simple: power on the AED. You’ll either open the lid or press a big, obvious power button. The second you do, the machine will come to life and start talking you through everything with clear voice prompts. From this moment on, you’re not alone. Just listen and follow its lead.

Create a Clear Workspace

Before you do anything else, you need to get to the person’s chest. The electrode pads require direct contact with bare skin to work. Don't waste precious seconds trying to unbutton a shirt. Your AED kit should have trauma shears—use them. Cut the clothing right up the middle and get it out of the way.

Next, you need a dry chest. If the person is wet from sweat, rain, or being in water, you have to wipe them down. Grab a towel, a spare shirt, anything, and dry the chest area quickly. This is critical for the pads to stick and for the electrical therapy to be effective.

Key Takeaway: Don't hesitate. Time is everything. Cutting clothing and acting fast are far more important than modesty or saving a shirt. Your only job is to get those pads on bare, dry skin as quickly as possible.

Address Common Obstacles

Emergencies are messy and unpredictable. You might run into a few things that need a quick fix before you can place the pads. Knowing what to look for ahead of time will keep you moving without losing your rhythm.

• Excessive Chest Hair: A very hairy chest can be a problem, preventing the pads from making good contact. Most AED kits include a small razor for this exact scenario. If you see it’s an issue, give a quick shave only on the spots where the pads need to go.
• Medication Patches: Look for any medication patches on the chest, like nicotine or pain relief patches. You have to remove them and wipe the skin clean before applying an AED pad. Leaving a patch on can block the shock or even cause a skin burn.
• Pacemakers or Implanted Devices: You might see or feel a hard lump under the skin, usually on the upper left side of the chest below the collarbone. This is likely a pacemaker or another implanted device. Do not place an AED pad directly on top of it. Just move the pad an inch or so to the side of the device.

Taking a few seconds to handle these things ensures the AED can do its job properly. It's why knowing what comes in your kit is so important, and it all starts with understanding how to buy an AED in the first place.

Once the chest is bare, dry, and clear of any obstacles, you’re ready for the most important step: applying the pads.

Mastering Correct AED Pad Placement

You’ve powered on the device and prepared the person’s chest. Now for what might be the most important hands-on step of learning how to use an AED device: applying the electrode pads.

Getting this right is what allows the machine to analyze the heart and deliver a shock, so don't rush it. Take a deep breath and just follow the pictures on the pads themselves.

The good news? The pads are your best guide. They have clear diagrams printed directly on them, showing you exactly where each one goes. Your job isn't to memorize complex anatomy—it's simply to match the pictures.

Standard Pad Placement for Adults

For most adults and older children, you'll use what's known as anterolateral placement. It sounds technical, but it’s actually very straightforward.

1. Upper Right Pad: Take one pad and place it on the person’s upper right chest, just below their collarbone. A good landmark is to place it just above the right nipple.
2. Lower Left Pad: The second pad goes on the person’s lower left side. Place it a few inches below their left armpit, right on the side of their rib cage.

Press down firmly on both pads to make sure they stick completely to the skin. Good, solid contact is essential. The goal is to create a clear electrical path that travels directly through the heart, and this placement achieves that perfectly.

This image shows exactly how to attach the pads to a bare chest.

As you can see, this placement creates a direct line for the electrical current to pass through the heart.

Special Considerations for Children and Infants

What if the person is a child or an infant? We generally define this as anyone under 8 years old or weighing less than 55 pounds. In these cases, the standard adult placement might not work because the pads could touch each other.

If the pads are too big for the child's torso, you'll need to switch to an anteroposterior placement.

Pro Tip: If you have them, use pediatric pads for children. They deliver a lower-energy shock. But if you only have adult pads, it is always better to use them than to do nothing at all.

For this front-and-back method:

• Place one pad in the center of the child’s chest.
• Place the other pad directly on their back, between the shoulder blades.

This adjustment ensures the heart is still situated between the two pads, but without the risk of them touching. This is a key skill we practice on different-sized manikins when you're getting your CPR and AED certification.

Acting fast with an AED is a true game-changer. Research shows that defibrillation within the first few minutes of cardiac arrest can boost survival rates from under 10% to around 70%. Modern, user-friendly designs with clear voice prompts have made these devices a cornerstone of emergency response that almost anyone can use.

Once the pads are correctly in place, the AED will immediately recognize it and prompt you for the next step: analysis.

Following AED Prompts for Analysis and Shock

Once those pads are stuck firmly in place, you’ve essentially handed the reins over to the AED. This is a huge relief. Your main job now shifts to being a good listener and following its calm, clear instructions to the letter. This is where the machine truly takes the lead, walking you through the most critical parts of the rescue.

The device will immediately tell you it's analyzing the person’s heart rhythm. You’ll hear a prompt like, "Analyzing heart rhythm, do not touch the patient." This isn't a suggestion—it's a direct command.

It is absolutely critical that everyone stands clear. Even a slight touch or the smallest movement can throw off the AED's reading of the heart's electrical activity. If you're the one leading the rescue, make sure you state loudly and clearly, "Analyzing now, nobody touch the person!"

Understanding the AED's Decision

After a few tense seconds of analysis, the AED will make its call and announce one of two outcomes. What you do next is dictated entirely by what that machine tells you.

• "Shock Advised": This means the AED has picked up on a chaotic, unproductive rhythm like Ventricular Fibrillation (VFib). The heart is just quivering, not actually pumping blood, and an electrical shock is the only thing that can potentially reset it.
• "No Shock Advised": This means the person's heart isn't in a shockable rhythm. It might be beating very faintly, or it may have stopped entirely (asystole). In this situation, a shock simply wouldn't help.

If you hear "No Shock Advised," don't get discouraged. It doesn’t mean the situation is hopeless. It just means the immediate next step is different. The AED will immediately tell you to begin or resume chest compressions. We cover these crucial next steps in our guide on the CPR steps for adults.

Safely Delivering the Shock

If the machine determines a shock is necessary, it will start to charge. You’ll often hear a distinct rising tone, like a capacitor powering up. As soon as it's ready, a prominent "Shock" button will begin to flash.

Before you even think about pressing that button, you have to perform one final, vital safety check.

1. Shout, loudly and clearly, "Everybody clear!" or simply "Clear!"
2. Do a quick visual sweep with your eyes from the person's head down to their toes. Make sure no one—including yourself—is touching them.
3. Once you are absolutely certain everyone is clear, press the flashing "Shock" button.

You’ll see the person’s body jolt or convulse as the electricity is delivered. This is completely normal. The second the shock is complete, the AED will immediately prompt you to get right back on the chest and start compressions again.

This incredible technology is becoming more common every single day. The global AED market was valued at about USD 3.51 billion in 2023 and is projected to nearly double by 2030, largely because of more devices being installed in public places. Learn more about the growth of the AED market. This increased availability makes it far more likely that a bystander like you can be the one to make a difference.

Continuing Care After the Shock

The shock has been delivered. You saw the person's chest jolt, and for a tense moment, everything goes still. But this isn't the end of the rescue—it's the start of an equally critical phase. Your job isn't done.

In fact, what you do in the minutes that follow is just as important as the shock itself.

The single most important rule now is to listen to the AED. It will almost always give you your next command right away: begin or resume chest compressions. This can feel strange. If the shock worked, why do they still need CPR?

Think of a successfully shocked heart like a marathon runner who just collapsed at the finish line. It’s exhausted and incredibly weak. The shock may have reset the chaotic rhythm, but the heart muscle doesn't have the strength to pump blood effectively on its own yet. Your CPR is what pushes that vital, oxygenated blood to the brain and other organs, keeping them alive while the heart tries to recover.

The Two-Minute Cycle

The AED is designed to guide you through a continuous loop of care. This cycle is the standard for emergency response and is built to give the person the best possible chance of survival until paramedics arrive.

It will typically instruct you to perform CPR for two minutes. Many devices even have a built-in metronome—a steady beeping sound—to help you keep the perfect pace for your compressions. Just push hard and fast in the center of the chest and let the machine keep time.

At the end of that two-minute CPR cycle, the AED will announce that it is re-analyzing the heart rhythm. Just like before, you must stop compressions and ensure no one is touching the person. The machine will then decide if another shock is needed or if you should continue CPR.

This "CPR-analyze-shock" loop repeats until one of two things happens: emergency responders arrive and take over, or the person shows obvious signs of life, like purposeful movement or normal breathing.

What to Do if They Start Breathing Normally

In the best-case scenario, the person may start to breathe normally on their own. If this happens, you can stop CPR. But do not remove the AED pads. The person is still in a very fragile state, and there’s always a chance they could go back into cardiac arrest.

Your next move is to place them in the recovery position. Carefully roll them onto their side, using one of their hands to support their head. This simple position keeps their airway open and prevents them from choking if they vomit.

Keep monitoring their breathing closely, leaving the pads attached the whole time. If they stop breathing normally again, immediately roll them back onto their back and let the AED re-analyze their heart rhythm.

Performing these steps with confidence is key. Knowing precisely how to deliver high-quality CPR and manage the scene after a shock are skills that come from hands-on practice. Exploring how to get CPR certified through a course with Ready Response can give you the muscle memory and assurance to act decisively when it matters most.

Common Questions About How to Use an AED Device

Even with an AED's simple voice prompts, a real-life emergency is a whole different ball game. It’s totally normal for your mind to race with "what if" scenarios. Let's walk through some of the most common questions I hear in my training sessions so you can feel confident when it really counts.

Can I Accidentally Shock Someone Who Doesn't Need It?

This is the number one fear I hear, and the answer is a firm no. You absolutely cannot accidentally shock someone who doesn't need it.

Modern AEDs are incredibly smart. They are built to only advise a shock if they detect a specific, life-threatening heart rhythm—like ventricular fibrillation. If the person's heart is beating normally, or if they are in flatline (asystole), the device will clearly state, "No Shock Advised." It then immediately tells you to start CPR. The machine removes all the guesswork and makes the critical call for you.

What if I Put the AED Pads on Incorrectly?

In the middle of a chaotic scene, nobody expects perfection. Doing your best is always, always better than doing nothing at all. The electrode pads have very clear pictures printed right on them showing exactly where to place them—use those diagrams as your guide.

But what if you're off by an inch or two? The most important thing is to act fast. If the pads don't have good contact with the skin, most modern AEDs will actually detect the poor connection and tell you to check the pads.

Here's what I tell every class: Applying the pads imperfectly is a thousand times better than hesitating and not using the AED at all. The goal is to get the machine connected and analyzing the heart's rhythm as fast as possible.

Can I Use an AED in the Rain or on a Metal Surface?

Yes, you can, but you need to take a couple of simple safety precautions. These situations are very manageable.

• In Wet Conditions: If the person is lying in a puddle, your first step is to quickly pull them to a drier spot. Before you apply the pads, you must wipe their chest dry with a towel, your shirt, or whatever you have. The pads need to stick firmly to the skin. The rain itself isn't a danger to you or the device.
• On Metal Surfaces: It is safe to deliver a shock on a metal surface, like stadium bleachers. The electrical current is designed to flow directly from one pad to the other through the person's chest, not through the surface they're on. The critical safety step here is ensuring no one is touching the person when the shock is delivered.

Do I Really Need Training to Use an AED?

Legally, you don't need a formal certification to use an AED on someone in an emergency. These devices were created for any bystander to use just by following the calm voice prompts. However, getting trained gives you a massive advantage. Having a foundational knowledge of emergency response, much like understanding general healthcare sector information, provides context and builds confidence.

Taking a hands-on CPR and AED course builds muscle memory. It helps you work faster, deliver higher-quality CPR, and manage the entire scene with a level head. That confidence can make all the difference in a person's chances of survival.

Ready Response provides the hands-on, expert-led training that transforms hesitation into decisive, life-saving action. Our courses give you the confidence to use an AED correctly and perform high-quality CPR when seconds matter most. Find a course near you and become the person who knows exactly what to do.