If an adult is unresponsive and is not breathing normally or is only gasping, call 911, begin CPR, and have someone retrieve an automated external defibrillator (AED). When the AED arrives, turn it on, attach the pads as shown, and follow its voice prompts. Deliver a shock only if the AED instructs you to do so, and resume CPR immediately afterward.
An AED is a portable device that analyzes the heart’s rhythm during suspected sudden cardiac arrest. If the AED detects a rhythm that may respond to defibrillation, it will instruct the rescuer to deliver a shock. An AED will not advise a shock for every person in cardiac arrest.
This guide explains how to use an AED on an adult. It is intended as an educational refresher and does not replace hands-on CPR and AED training, the instructions from a 911 dispatcher, or the prompts provided by the AED.
Quick Answer: How Do You Use an AED?
- Make sure the scene is safe.
- Check the person for responsiveness and normal breathing.
- Call 911, send someone to retrieve an AED, and begin CPR.
- Turn on the AED and follow its voice prompts.
- Expose and dry the chest, then attach the pads as pictured.
- Stand clear while the AED analyzes the heart rhythm and deliver a shock only if instructed.
- Resume CPR immediately and continue following the AED prompts.
Emergency reminder: Do not delay CPR while waiting for an AED. If another person is present, have that person call 911 and retrieve the AED while you begin chest compressions.
What Is an AED?
An automated external defibrillator is designed to help a person experiencing sudden cardiac arrest. Once its adhesive pads are attached to the person’s bare chest, the AED analyzes the heart’s electrical activity and determines whether a shock is advised.
The primary parts of a typical AED include:
- Adhesive pads: Pads that attach to the chest and allow the AED to analyze the heart rhythm and deliver a shock when appropriate.
- Power and shock controls: Depending on the model, the device may have a power button, a shock button, or fully automatic controls.
- Voice and visual prompts: Instructions that guide the rescuer through pad placement, rhythm analysis, shock delivery, and CPR.
- Pad connector: Some models require the pad cable to be plugged into the AED before analysis can begin.
AED models vary, so always follow the pictures on the pads and the instructions provided by the specific device.
How to Use an AED in 7 Steps
The following steps describe a general adult CPR and AED response. Follow the instructions from the 911 dispatcher and the voice or visual prompts from the AED throughout the emergency.
Step 1: Make Sure the Scene Is Safe
Before approaching the person, look for immediate dangers that could harm you, the person, or nearby bystanders. Possible hazards include moving traffic, fire, electrical equipment, gas, falling objects, or standing water.
Do not enter an unsafe area. If the scene is dangerous, call 911 and wait for trained emergency personnel.
Step 2: Check Responsiveness and Breathing
Tap the person’s shoulders and shout, “Are you okay?” If the person does not respond, check whether they are breathing normally.
Occasional gasps are not normal breathing. If the person is unresponsive and is not breathing normally or is only gasping, treat the situation as suspected cardiac arrest and act immediately.
Step 3: Call 911, Get an AED, and Begin CPR
Tell a specific bystander to call 911 and retrieve the nearest AED. Point to the person and give a direct instruction, such as, “Call 911 and bring the AED.”
If you are alone with an adult, call 911 and place the phone on speaker if possible. Follow the dispatcher’s instructions and begin CPR. Do not leave the person to search for an AED unless the dispatcher instructs you to do so or an AED is immediately accessible.
Start chest compressions in the center of the chest. Push hard and fast at a rate of 100 to 120 compressions per minute, allowing the chest to return to its normal position after each compression. For an adult, compress the chest at least 2 inches deep while avoiding excessive depth.
If you are not trained or are unable to provide rescue breaths, perform continuous hands-only CPR until the AED is ready or emergency medical services take over. If you are trained and willing to provide breaths, use cycles of 30 compressions and 2 breaths.
Step 4: Turn On the AED
As soon as the AED arrives, place it near the person’s shoulder and turn it on. Open the lid or press the power button, depending on the model.
Listen carefully to the voice prompts. If another rescuer is available, one person should continue CPR while the other turns on the AED and prepares the pads. Interrupt chest compressions for as little time as possible.
Step 5: Expose the Chest and Attach the AED Pads
Remove clothing covering the chest. If the chest is wet, dry it quickly so the pads can adhere properly.
Remove the backing from each pad and place the pads on the bare chest as shown in the diagrams printed on them:
- Place one pad on the upper-right side of the chest, below the collarbone.
- Place the other pad on the lower-left side of the chest, several inches below the left armpit.
Press the pads firmly against the skin and make sure they are fully attached. Plug the pad cable into the AED if the device instructs you to do so.
Step 6: Stand Clear and Deliver a Shock if Advised
When the AED begins analyzing the heart rhythm, stop CPR and make sure no one is touching the person. Say, “Clear,” loudly and visually confirm that everyone has moved away.
If the AED advises a shock, continue to make sure no one is touching the person. Press the flashing shock button when instructed. A fully automatic AED may deliver the shock without requiring the rescuer to press a button, so listen closely to its warning and prompts.
If the AED says that no shock is advised, do not remove the pads. A “no shock advised” message does not mean the emergency is over.
Step 7: Resume CPR Immediately
Immediately resume CPR after a shock or a “no shock advised” prompt. Begin with chest compressions and continue until the AED tells you to stop for another rhythm analysis.
Continue following the AED prompts and performing CPR until:
- Emergency medical professionals take over.
- The person begins to move, respond, or breathe normally.
- The scene becomes unsafe.
- You are physically unable to continue.
If the person begins breathing normally but remains unresponsive, follow the 911 dispatcher’s instructions and continue monitoring their breathing. Leave the AED pads attached until emergency medical personnel take over.
AED Pad Placement and Special Situations
What If the Person’s Chest Is Wet?
Move the person away from standing water when it is safe to do so and quickly dry the chest before attaching the pads. An AED can be used in rain or a damp environment when precautions are taken, but the pads must adhere securely and no one should be touching the person during rhythm analysis or shock delivery.
What If the Person Has a Hairy Chest?
Heavy chest hair may prevent AED pads from adhering properly. Follow the instructions in the AED kit. Some kits include a razor. If instructed, shave only the areas where the pads will be placed. If a pad has already been applied and does not adhere, a second set of pads may be needed.
What If There Is a Medication Patch?
Do not place an AED pad directly over a medication patch. Wearing protective gloves when available, remove the patch and wipe the area before attaching the AED pad. Avoid direct contact with medication from the patch.
What If the Person Has a Pacemaker?
An implanted pacemaker or defibrillator may create a visible or noticeable lump beneath the skin, usually in the upper chest. Do not place an AED pad directly over the implanted device. Position the pad at least one inch away while following the AED pad diagram.
Can You Use an AED on a Child or Infant?
An AED may be used on a child or infant experiencing suspected cardiac arrest. Use pediatric pads or the AED’s pediatric setting when they are available and appropriate for the child’s age or size. Follow the illustrations on the pads and the device’s prompts.
If pediatric pads are unavailable, an adult AED may still be used according to current CPR training and the device manufacturer’s instructions. If the pads could touch on a small chest, the diagrams may direct you to place one pad on the chest and the other on the back between the shoulder blades.
CPR response steps for children and infants differ from adult CPR in some situations. Follow the 911 dispatcher’s instructions and obtain pediatric CPR/AED training for complete, hands-on guidance.
What About Oxygen, Jewelry, or an Underwire Bra?
Keep supplemental oxygen equipment away from the person’s chest before a shock is delivered. Move necklaces or other items if they interfere with pad placement, but do not delay CPR or AED use to remove unrelated jewelry.
Remove or cut clothing as necessary to expose the chest. If a bra interferes with the required pad positions, move or remove it so both pads can adhere completely to bare skin.
Common AED Mistakes to Avoid
- Waiting for the AED before beginning CPR: Start CPR immediately and use the AED as soon as it becomes available.
- Placing pads over clothing: AED pads must be attached directly to the person’s bare chest.
- Touching the person during analysis: Movement can interfere with the AED’s ability to analyze the heart rhythm.
- Failing to clear the person before a shock: Make sure no one is touching the person when a shock is delivered.
- Delaying CPR after a shock: Resume chest compressions immediately after the AED delivers a shock.
- Stopping after “no shock advised”: Resume CPR and continue following the AED prompts unless the person shows signs of life or emergency professionals take over.
- Removing the pads too soon: Leave the pads attached so the AED can continue its rhythm-analysis cycles.
Frequently Asked Questions About AED Use
Can anyone use an AED?
Yes. AEDs are designed to guide members of the public through an emergency using voice prompts, pictures, and visual instructions. CPR and AED training is still strongly recommended because hands-on practice can help a rescuer respond more quickly and confidently.
When should an AED be used?
Use an AED when a person is unresponsive and is not breathing normally or is only gasping. Call 911, begin CPR, and use the AED as soon as it is available. Do not use an AED on someone who is responsive and breathing normally.
Can an AED shock someone who does not need it?
An AED analyzes the heart rhythm and advises a shock only when it detects a rhythm that may respond to defibrillation. The rescuer should never press the shock button unless instructed by the AED.
Do you perform CPR before or after using an AED?
Begin CPR immediately after recognizing suspected cardiac arrest and continue until the AED is ready to analyze the heart rhythm. After the AED delivers a shock—or announces that no shock is advised—resume CPR immediately.
What does “no shock advised” mean?
“No shock advised” means the AED did not detect a heart rhythm that should receive a shock at that moment. It does not necessarily mean the person has recovered. Resume CPR immediately and continue following the AED and 911 dispatcher’s instructions.
Should you remove AED pads after delivering a shock?
No. Leave the pads attached and continue following the AED prompts. The device will instruct rescuers when to pause CPR so it can analyze the heart rhythm again.
Can you use an AED on a pregnant person?
Yes. Pregnancy should not delay CPR or AED use when a person is experiencing suspected cardiac arrest. Place the pads in their standard positions and follow the AED and 911 dispatcher’s instructions.
When should you stop CPR?
Continue CPR until emergency medical professionals take over, the person begins to respond or breathe normally, the scene becomes unsafe, or you are physically unable to continue. Follow the instructions provided by the 911 dispatcher and AED.
CPR / AED / FIRST AID TRAINING
Reading the AED steps can help reinforce the response process, but hands-on training gives participants an opportunity to practice recognizing cardiac arrest, performing chest compressions, delivering rescue breaths, placing AED pads, and following AED prompts.
Firefighter Safe CPR/AED/First Aid training helps individuals, community members, workplace safety teams, and other groups develop practical emergency-response skills. Training options include:
- Adult CPR/AED training
- Adult and child CPR/AED training
- Adult, child, and infant CPR/AED training
- Combined CPR, AED, and first aid training
- Community, workplace, and group training options
Individual CPR, AED, and first aid training is also available through Firefighter Safe’s community classes. Visit the CPR training page or contact Firefighter Safe to discuss current course options, scheduling, and certification needs.
AED Guidance Sources
This article is based on general adult CPR and AED guidance from recognized emergency-care organizations. Always follow the directions of emergency dispatchers, trained medical professionals, and the manufacturer of the AED being used.
Medical and safety information should be reviewed periodically as CPR and emergency-care guidance changes. Before publishing, Firefighter Safe should have this article reviewed by a currently credentialed CPR/AED instructor and display the reviewer’s name, relevant credential, and most recent review date.