Modern AEDs are engineered around a single design principle: a person who has never seen one before should still be able to save a life with it. The voice prompts, visual indicators, and pad packaging are all built for that exact moment of panic. Even with that engineering, knowing the eight-step operating sequence ahead of time materially improves response speed, and response speed is the single biggest predictor of survival in cardiac arrest. According to the American Heart Association, every minute of delay in defibrillation reduces survival probability by roughly 10%. Knowing the procedure shaves seconds. Seconds save lives.
This guide walks through the complete AED operating sequence, the AHA Chain of Survival framework that surrounds it, pad placement specifics, pediatric considerations, the special-case scenarios most bystanders worry about, and what every voice prompt actually means.
The AHA Chain of Survival, where the AED fits
The American Heart Association’s Chain of Survival is the canonical framework for cardiac arrest response. The AED is the third link. Without the first two, the AED can’t save a life. Without the AED, links four and five (advanced care and recovery) usually can’t either.
| Link | Action | Who performs it | Timeframe |
|---|---|---|---|
| 1 | Recognition + call 911 | Bystander | 0 to 60 seconds from collapse |
| 2 | Early CPR (chest compressions) | Bystander | Begin within 60 seconds |
| 3 | Early defibrillation (AED) | Bystander or first responder | Within 3 minutes , AHA target |
| 4 | Advanced care (EMS, paramedics) | EMS | Average 7 to 14 min response |
| 5 | Post-cardiac-arrest care (hospital) | Hospital | Days to weeks |
None of this works if the pads are out of date.
The conductive gel dries and adhesion fails, so a pad that will not sit flat cannot deliver its energy properly. Check yours against the printed date.
All models: pads and battery costs · Philips parts · ZOLL parts
The 8-step bystander AED protocol
The complete sequence from collapse to first shock. Practice this mental walkthrough before you ever need it.
1
Recognize cardiac arrest
Look for: sudden collapse, unresponsiveness (tap shoulder, shout), no normal breathing (gasping is not breathing). If all three are present, treat as cardiac arrest. Don’t wait for a pulse check , non-medical bystanders frequently miss weak pulses.
2
Call 911 (or have someone call)
Speak clearly: “Cardiac arrest” + address + nearest landmark. If you’re alone, put the phone on speaker and stay with the patient. If a second person is present, send them to call while you start CPR.
3
Retrieve the AED + start CPR immediately
If anyone is nearby, send them for the AED while you begin chest compressions. Hands in the center of the chest, push hard and fast (100 to 120 compressions per minute, ~2 inches deep). Don’t wait for the AED to start.
4
Turn the AED on
Open the cabinet (alarm may sound, ignore it). Press the power button (or open the lid, some models power on automatically). Voice prompts begin immediately.
5
Expose the chest
Remove or cut through clothing. Wipe the chest dry if wet. Shave if extremely hairy (most AEDs include a razor in the cabinet). Remove medication patches with a gloved hand or cloth. Set jewelry aside.
6
Open and apply the pads
Open the pad packaging. Peel the backing. Apply pads exactly as shown on the diagram printed on each pad: one upper-right chest (below the collarbone), one lower-left chest (below the armpit, on the ribs). Plug the pad cable into the AED if not pre-connected.
7
Stand clear, let the AED analyze
The AED says, “Analyzing, do not touch the patient.” It evaluates heart rhythm in ~10 seconds. If shock is advised, it announces and either delivers automatically (fully-automatic AED) or prompts you to press the shock button (semi-automatic). Make sure no one is touching the patient before the shock.
8
Resume CPR immediately
After the shock, or if “no shock advised”, resume chest compressions immediately. The AED will re-analyze every 2 minutes. Continue this cycle until EMS arrives or the patient shows signs of life (movement, breathing).
Pad placement, the most-asked detail
Pad placement is printed on the pad itself with a clear diagram, but the standard placement is:
- Upper pad: Right side of the patient’s chest, just below the collarbone, slightly to the side of the breastbone.
- Lower pad: Left side of the patient’s chest, below the armpit, on the ribcage.
The pads create a diagonal electrical path through the heart. If pads are reversed (lower-left and upper-right swapped), the AED still works, current still passes through the heart. Don’t waste time repositioning correctly oriented pads.
Pediatric AED use
Children under approximately 8 years or 55 lb (25 kg) should receive reduced shock energy. Three pathways exist depending on the AED model:
| Pathway | How it works | Examples |
|---|---|---|
| Pediatric pads | Separate pad set with attenuated energy | ZOLL Pedi-Padz II, Defibtech Pediatric, Philips OnSite Pediatric (M5072A) |
| Pediatric key | Insert a key to switch the device into pediatric mode using adult pads | Philips HeartStart FRx Infant/Child Key |
| Adult/Child toggle | Single pad set, child mode activated by button | Physio-Control LIFEPAK CR2 (Quik-Step) |
If pediatric pads are not available in a true emergency, use adult pads on a child, placing them front-to-back to avoid pad overlap. Adult-to-pediatric is still better than no defibrillation. The AHA 2025 Guidelines explicitly permit this.
For infants under 1 year, the AHA prefers manual defibrillation by a healthcare provider if available, but if only a public AED is on hand, pediatric pads are used.
Special-case scenarios
Patient is wet (pool, rain, sweat)
Move the patient to a dry surface if possible. Wipe the chest dry before applying pads. AEDs can be used in light rain or snow per AHA 2025 guidelines. Avoid standing water, the rescuer should not be in contact with conductive water.
Patient has a pacemaker or an implanted defibrillator
You’ll see a visible lump under the skin and possibly a small scar near the collarbone. Place the AED pad at least 1 inch away from the device. Proceed normally.
Patient is pregnant
AED use during pregnancy is fully indicated. Place pads in standard positions. Defibrillation does not harm the fetus. The mother’s survival is the priority.
The patient has a hairy chest
If pads won’t stick due to chest hair, press firmly and rip off , the hair comes with the pads. Apply a backup set of pads. Most AED cabinets include a small disposable razor for this purpose.
Patient is wearing jewelry or has piercings
Remove necklaces if they’re in the pad placement zone. Otherwise, leave jewelry alone, don’t waste time. Nipple piercings should be uncovered before pad placement.
Patient is on a metal surface
Place pads as normal. The metal surface doesn’t affect AED function, current still flows through the patient. If possible, move them to a non-conductive surface, but don’t delay defibrillation.
Patient has a transdermal medication patch
Remove the patch with a gloved hand or cloth before placing the pad. Patches can interfere with shock delivery and cause skin burns.
The voice prompt translation
Different AED brands phrase prompts slightly differently. Here’s what the common phrases actually mean:
| What the AED says | What it means | What you do |
|---|---|---|
| “Apply pads to bare chest.” | Open packaging, place pads per diagram | Follow the diagram on the pad |
| “Plug in connector.” | The pad cable is not yet connected to the AED | Plug the cable in |
| “Stand clear, analyzing.” | AED is reading the heart rhythm | Do not touch the patient · ~10 seconds |
| “Shock advised, charging” | Patient is in a shockable rhythm | Continue standing clear |
| “Stand clear, press the orange button.” | Semi-auto: deliver shock | Verify no one is touching, press the button |
| “Shock delivered” (or sound) | Shock complete | Resume CPR immediately |
| “No shock advised, begin CPR.” | Rhythm not shockable (could be asystole, PEA, or organized rhythm) | Continue CPR, AED will re-analyze in 2 min |
| “Push harder” / “Good compressions” (ZOLL) | CPR depth feedback | Adjust compression depth |
Common mistakes to avoid
✓ Do
- Start CPR immediately, even before the AED arrives
- Push hard and fast, 100 to 120 per minute
- Apply pads exactly per the diagram
- Stand clear during analysis and shock
- Resume CPR within seconds of the shock
- Continue the cycle until EMS or the patient revives
✗ Don’t
- Delay CPR while waiting for an AED
- Stop compressions to check for a pulse repeatedly
- Touch the patient during analysis or shock
- Be afraid of “doing it wrong”, AEDs only shock when needed
- Move the patient unnecessarily
- Remove pads after a shock, leave them on
What if the AED says “no shock advised”?
This is one of the most misunderstood prompts. It does not mean the patient is fine. It means the heart is not in a shockable rhythm, likely asystole (flatline), pulseless electrical activity (PEA), or an organized rhythm. The patient still needs CPR. Continue compressions until the AED re-analyzes (every 2 minutes) or EMS arrives.
For deeper context, see our “AED Says No Shock Advised, What It Means” article.
Real-world outcomes when AEDs are used quickly
Real-world case
Damar Hamlin, January 2023
NFL safety Damar Hamlin collapsed in cardiac arrest during a Monday Night Football game. Sideline medical staff started CPR and used an AED on the field. Hamlin survived and resumed his NFL career the following season. The case became one of the most-cited modern examples of why on-site AED access plus trained CPR responders save lives.
70%+
Survival rate when AED is used within 3 minutes of collapseSource: American Heart Association
~10%
Survival drop per minute of defibrillation delaySource: AHA Public Access Defibrillation data
~12%
Survival without bystander interventionReplacing your AED pads or battery
AED pads and batteries expire on a fixed schedule whether the device is ever used or not, and they are the single most common reason an AED fails when it is needed. In the largest published analysis of FDA-reported AED events, 40,787 cases, batteries accounted for 23.2 per cent of failures and pads and connectors for 23.7 per cent, so 46.9 per cent of all AED failures are consumables (DeLuca et al., Annals of Emergency Medicine, 2012, PMID 21872969). Below is every current replacement part with its price and service life, verified against seller product data on 12 September 2026.
Model Adult pads Battery Pediatric option 10 year consumable cost Philips HeartStart OnSite M5071A $99.00, 2 years M5070A $249.00, 4 years Separate M5072A cartridge, prescription only About $894 Philips HeartStart FRx SMART Pads II 989803139261 $89.00, 2 years M5070A $249.00, 4 years Infant/Child Key $139.00, reusable About $854 ZOLL AED Plus CPR-D Padz 8900-0800-01 $230.00, 5 years Lithium set of 10 $100.00, 5 years Pedi-padz II $155.00, 2 years About $330, the lowest we track ZOLL AED 3 CPR Uni-padz 8900-000280-01 $234.00, 5 years 8000-000696 $201.00, 5 years None needed, Uni-padz cover children About $435 Defibtech Lifeline DDP-100 $75.15 DBP-1400, part DCF-200 $229.10 DDP-200P $130.25 About $530 Defibtech Lifeline VIEW DDP-2001 $83.05 DCF-2003 $240.45 DDP-2002 $136.40 About $813 HeartSine Samaritan PAD Pad-Pak-01 $236.00, pads and battery in one cartridge Included in the Pad-Pak, there is no separate battery Pediatric Pad-Pak PAD-PAK-02 $279.00 About $472 Cardiac Science Powerheart G5 XELAED001C $88.00 XBTAED001A $495.00, 4 years XELAED003C $127.00 About $1,342, the highest we track Physio-Control LIFEPAK CR2 Quik-Step 11101-000021 $196.00, adult and child in one set LIFEPAK CR2 lithium battery $341.00, about 4 years None needed, the Quik-Step set covers children Not published per part Prices verified against the public product data of AED Leader on 30 September 2026. Service life is the manufacturer figure where one is published; where it is not, check the expiry date printed on the part itself. Ten year consumable cost is our own calculation from those part prices and service lives.
Three things owners get wrong
- Buying the wrong Philips pad. The FRx uses SMART Pads II, part 989803139261. SMART Pads III belong to the FR3, a different device. The OnSite uses M5071A and the two are not interchangeable.
- Assuming the pediatric part is optional. On a ZOLL AED Plus, Pedi-padz II cost $155.00 and last two years, which is about $775 across a ten year life. On a ZOLL AED 3 or a LIFEPAK CR2 the pads already cover children and that cost is zero.
- Tracking the wrong date. HeartSine combines the pads and battery into one Pad-Pak cartridge, so there is a single expiry to track. Every other model here has two parts on two separate clocks.
Full replacement schedule by model is on our AED pads and batteries page. If you are still choosing a device, the ten year running cost is usually a bigger number than the discount you are negotiating: see every AED brand ranked by price and ten year cost.
Recertified prices across all seven models
Recertified units are the same models under the same FDA premarket approvals, restored, tested and sold with a minimum three year warranty.
Model New Recertified You keep Buy Philips HeartStart OnSite $1,589 $875 $714 (45%) AED Leader or Response Ready Philips HeartStart FRx $2,099 $875 $1,224 (58%) AED Leader or Response Ready ZOLL AED Plus $2,082 $875 $1,207 (58%) AED Leader or Response Ready ZOLL AED 3 $2,399 $1,150 $1,249 (52%) AED Leader or Response Ready HeartSine Samaritan PAD 350P $1,411 $875 $536 (38%) AED Leader or Response Ready HeartSine Samaritan PAD 450P $1,761 $875 $886 (50%) AED Leader or Response Ready Cardiac Science Powerheart G5 $2,157 $1,225 $932 (43%) AED Leader or Response Ready Prices verified 30 September 2026 against the public product data of both stores. Both list identical recertified prices, so buy from whichever fits your order size: AED Leader for one to four units, Response Ready for five or more and for compliance and fleet programmes. New prices are the AED Leader list price on the same date.
The honest risk. A recertified AED is a used device. The three year minimum warranty is what makes the saving worth taking. Read recertified versus new and how to choose a refurbished AED before you decide.
Source: AHA Out-of-Hospital SCA statistics
What to do after EMS arrives
- Leave the AED pads attached, EMS will continue using them or transition to their own equipment
- Be ready to brief responders: time of collapse, time AED was applied, number of shocks delivered, any medications visible
- Don’t move the patient until EMS instructs
- If possible, retain the AED for event-data download, the device logs every action and shock delivered
Frequently Asked Questions
How do you use an AED step by step?
The 8-step bystander protocol: (1) recognize cardiac arrest, (2) call 911, (3) retrieve AED + start CPR, (4) turn on the AED, (5) expose the chest, (6) apply pads per diagram, (7) stand clear and let the AED analyze and shock if advised, (8) resume CPR immediately. The device talks you through every step.
Where do the AED pads go on the body?
One pad goes on the upper right chest, just below the collarbone. The other goes on the lower left chest, below the armpit, on the ribcage. Each pad has a diagram showing exact placement. Adult pads in adult patients; pediatric pads in children under ~8 years or 55 lb.
Can you hurt someone by using an AED?
No. AEDs only deliver a shock when they detect a shockable rhythm (ventricular fibrillation or pulseless ventricular tachycardia). If the patient does not need a shock, the device will say “no shock advised.” It is designed to shock only these rhythms.
Can I use an AED on a child?
Yes. Use pediatric pads or pediatric mode (via the device’s key or switch) if available. For children under ~8 years or 55 lb without pediatric capability, adult pads can be used in an emergency, placed front-to-back to avoid overlap. Per AHA 2025 guidelines, this is acceptable when pediatric pads aren’t available.
How long does an AED analysis take?
Roughly 10 seconds. The device reads the patient’s heart rhythm and decides whether a shockable rhythm is present. During analysis, no one should touch the patient. CPR pauses briefly during analysis, then resumes immediately after shock delivery (or after “no shock advised”).
Do I keep doing CPR after the AED shock?
Yes, immediately. Resume chest compressions the second the shock is delivered, without checking for a pulse. Continue the cycle (CPR + AED re-analyzes every 2 minutes) until EMS arrives or the patient shows signs of life.
What if I’m wrong about what’s happening?
In most cases you’re protected. Every U.S. state’s Good Samaritan law extends civil immunity to bystanders acting in good faith. If you misjudge the situation, the AED itself will not shock a non-shockable rhythm. These protections have conditions that vary by state, such as acting in good faith and without gross negligence. The greatest risk is not using one when you should have.
Do I need training to use an AED?
No legal requirement. AEDs are explicitly designed for use by untrained bystanders with voice prompts. However, formal CPR/AED certification through AED Leader, AHA, or American Red Cross significantly improves confidence and response speed under stress, and is the difference between hesitation and action in the first 90 seconds.
Get hands-on AED training in under 3 hours.
Sources & References
- American Heart Association, 2025 CPR & ECC Guidelines
- American Heart Association, Cardiac Arrest Overview
- American Heart Association, Public Access Defibrillation Resources
- American Red Cross, CPR Steps
- FDA, AED Regulation & Guidance
- NIH, National Heart, Lung, and Blood Institute: What is cardiac arrest?
Disclaimer: This article is informational and not a substitute for hands-on CPR/AED training. Always call 911 in a real emergency. AEDs are FDA-regulated Class III medical devices.
