Automated external defibrillators (AEDs): how they work, vehicle use, training and upkeep
How to use an AED, keep it ready in a vehicle and follow your state’s rules
Safety Behind the Wheel Foundation built this guide from Centers for Disease Control and Prevention (CDC) guidance, American Red Cross AED steps, Food and Drug Administration (FDA) device rules and federal public access defibrillation guidelines, along with state AED laws and published cardiac arrest research. Every source is listed at the end.
What an AED is and how it works
Sudden cardiac arrest happens when the heart stops beating without warning, so blood no longer reaches vital organs such as the brain [1]. The person collapses, does not respond and does not breathe normally. Without fast help, the person will die.
An automated external defibrillator, or AED, is a portable device that checks the heart’s rhythm. When needed, it sends an electric shock to help the heart return to a working rhythm [2]. That shock is called defibrillation. The device speaks each step out loud.
The key safety feature is built in. An AED will not deliver a shock unless it detects a rhythm that a shock can treat [3]. You do not need to read a heart tracing. You turn it on, place the pads and follow the prompts.
The U.S. Food and Drug Administration (FDA) classifies AEDs as Class III medical devices, its strictest class, which need premarket approval [4]. The approved system includes the AED plus the battery, the pads and any key used for children [4]. Pads are the sticky electrodes placed on the bare chest. Buy replacement pads and batteries made for your model.
Some AEDs ask you to press a flashing shock button. Others count down and shock on their own. Know which kind you carry, and train on it.
Why minutes matter on the road and at work
More than 350,000 people in the United States have a cardiac arrest each year, according to the American Red Cross [2]. The odds of survival drop by about 7 to 10 percent for every minute without CPR or a shock [3, 5]. Once 10 minutes pass, the chance of a successful rescue is very small [3, 5].
That is why federal guidance calls 3 minutes or less the best response time [3]. CDC guidance says an AED should be ready for use within 3 to 5 minutes [1]. An ambulance may need longer, especially on rural roads or in heavy traffic.
In a large North American trial, community sites such as shopping malls trained volunteers either in CPR alone or in CPR plus AED use [6]. Sites with AEDs had twice as many people survive to leave the hospital: 30 of 128 compared with 15 of 107 [6]. The volunteers gave no shocks that were not needed [6].
Cardiac arrest can also strike behind the wheel. A seven year study in Osaka, Japan, found 179 cardiac arrests among drivers [7]. Of those, 78 had a medical cause, and about half of those seemed to begin while the person was driving [7]. One month later, 11.5 percent of drivers with a medical cause had survived with good brain function [7]. Only 2.0 percent of those whose arrest came from crash injuries did [7]. Some people found slumped in a wrecked car had a heart emergency first.
Who carries an AED, and where it does the most good
The first person to reach a cardiac arrest is often an officer, a tow operator or a coworker. A review of police AED programs found that people were about 1.4 times as likely to survive after officers began carrying AEDs [8]. Patients first shocked by police survived more often than those first shocked by EMS, at 39.4 percent versus 28.6 percent [8].
Comparison compiled by Safety Behind the Wheel Foundation
Where an AED does the most good
| Setting | Why an AED fits | Question to answer first |
|---|---|---|
| Fire engines and EMS units | Often first to arrive | Does every unit, including command vehicles, carry one? |
| Police and highway patrol cars | Shorter time to first shock [8] | Who checks the device each shift? |
| Tow trucks and roadside service patrols | Work at crash and breakdown scenes | Are operators trained in CPR and scene safety? |
| Road agency and utility crews | Work far from hospitals | How long would an ambulance take to reach your sites? |
| Transit hubs, rest areas and fleet yards | Many people pass through | Can the public open the cabinet at all hours? |
| Employers with staff who drive | People work alone or far away | Is there a trained person on every shift? |
Should a family keep an AED in the car? For most families, a CPR class is the best first step. A vehicle AED needs regular checks, fresh pads and protection from heat and cold. If someone in your home has a heart condition, ask their doctor whether an AED makes sense.
Choosing an AED for a vehicle, site or fleet
Choose simplicity over extra features. The best AED is the one your team can reach and use without fumbling. Look for:
- Approved system: Confirm the device, pads and battery are FDA approved to work together [4].
- Clear prompts: Voice prompts should be easy to hear over traffic noise. Some models also coach you through CPR.
- Child use: Check whether the model offers child pads or a child key [4].
- Toughness: For vehicles, look for a rating against dust, water and vibration, and read the temperature range in the manual.
- Easy status check: The ready light should be visible through the case.
- Data review: Federal guidelines call for the program’s medical director to review each use [3]. Saved event data makes that easier.
- One model per fleet: The same model everywhere makes training and spare parts simpler.
AEDs are sold through professional emergency equipment suppliers, authorized dealers for each maker, medical supply distributors and training organizations that offer program support. Ask about spare pads, batteries, training units and recall notices. Also ask about medical direction, meaning a licensed physician who oversees your program. Some states require it, including Washington [9].
Carrying an AED in a vehicle
A vehicle AED faces jolts, dust, heat and cold. Plan for each.
- Mount the case in a bracket or strap it down. A loose case can fly forward in a hard stop.
- Store it where the crew can grab it in seconds, not under cones or chains.
- Check the storage temperature range in the manual. In extreme heat or cold, bring the AED inside between shifts.
- Mark the vehicle and compartment so any responder knows an AED is on board.
- Check the status light at the start of every shift and log it.
- After any use, restock pads and supplies, file a report and return the device to service [3].
- Tell your local EMS agency and dispatch center which vehicles carry AEDs. Federal guidelines say EMS should know how many AEDs you have, what kind and where they are [3].
That last step lets dispatchers send the closest equipped unit, not only the closest ambulance.
Using an AED at a roadside or collision scene
At a roadside, your first job is to avoid becoming a second victim. Park well off the road, turn on hazard lights and watch traffic. Our guide to post crash care explains how to protect the scene and call 911.
Once the scene is as safe as you can make it, use this sequence:
- Check whether the person responds and breathes normally. If not, call 911 and send someone for the AED.
- Start CPR right away if you are trained. Push hard and fast in the center of the chest.
- Turn on the AED as soon as it arrives and follow its prompts.
- Bare the chest. Wipe it dry and remove any medicine patches [10].
- Place one pad on the upper right chest and the other on the lower left side, a few inches below the armpit [10]. If the pads might touch, place one on the front of the chest and one on the back [10].
- Make sure no one touches the person, and call out “Clear” before the AED checks the rhythm or shocks [10].
- After a shock, or if no shock is advised, restart CPR at once [10].
- Keep following prompts until EMS takes over or the person breathes normally.
The Red Cross adult steps apply to children 8 and older who weigh more than 55 pounds [10]. For younger children, learn the child steps in a class that covers children and infants. CDC estimates about 23,000 cardiac arrests in children each year [1].
What is different after a wreck
An AED cannot fix bleeding or broken bones. Cardiac arrests caused by crash injuries are less survivable than those with a medical cause [7]. Still, if a person is unresponsive and not breathing normally, use the AED. It will shock only if a shock can help [3].
Do not move an injured person unless they face danger, such as fire or traffic. If CPR is needed, follow the 911 dispatcher’s advice on positioning. Severe bleeding needs its own tools, covered in our companion guide on bleeding control kits.
Training that sticks
In the public access trial, volunteers with training used AEDs safely and saved more lives [6]. CDC notes that CPR from a bystander can make survival two to three times as likely [1].
Federal guidance says trained responders should take a formal refresher course no less than every two years [3]. CDC recommends a response team trained in CPR and AED use, with practice drills at least once a year [1]. Safety Behind the Wheel Foundation gives fleets and responders the same advice.
Build training around your real setting:
- Train on a practice unit that matches the model you carry.
- Time how long it takes to pull the AED from the vehicle and reach a patient 100 feet away.
- Practice at a roadside, with cones set and a lookout watching traffic.
- Rotate roles so each person practices calling 911, doing CPR and running the AED.
- Review every real use, with your medical director when possible [3].
OSHA has no rule written just for AEDs [5], but employers should still treat training as part of the purchase.
Maintenance and readiness checks
An AED that is locked away or out of date cannot help anyone. In 2025, researchers checked public AEDs in three high risk neighborhoods of Birmingham, Alabama [11]. Of 37 AEDs open to the public, none could be reached around the clock [11]. Five had expired batteries and pads, and two would not work [11].
Federal guidance says to check AEDs and their supplies routinely, and again after every use [3]. New York and Washington law tell owners to maintain and test AEDs by the maker’s standards [9, 12]. Use this checklist at each shift change or on a set weekly date.
Register each device with its maker so you get recall notices, and keep the check log with your program records.
Laws, liability and registration
As of October 2026, AED rules still differ widely by state. One research team counted 921 state and federal rules that touch community AED use, with large differences between states and few federal rules [13].
The federal Cardiac Arrest Survival Act gives civil immunity to people who use or try to use an AED in a perceived medical emergency [14]. Owners are also covered if they tell emergency responders where the device is, maintain and test it, and train employees who may use it [14]. It does not cover gross negligence or reckless, willful or criminal misconduct [14]. The federal law applies only where a state has no AED immunity law of its own for that group [14].
Comparison compiled by Safety Behind the Wheel Foundation
What three states ask of AED owners and users
| State | What the law asks of AED owners and users |
|---|---|
| New York | Register each AED’s location and type with the state health department, report every use to local EMS or the 911 center, post a sign at the main entrance, and name a trained person [12] |
| Washington | Train expected users in a state approved CPR and AED course, enlist physician medical direction, tell local EMS where the AED is, and call 911 after use [9] |
| Florida | Training and telling local EMS where the AED is are encouraged, not required. Anyone who uses an AED must call EMS as soon as possible [15] |
Before you place an AED, ask your state EMS office: Do you need to register it? Is medical direction required? Must training come from an approved course? Are signs or reports after each use required?
Limits and common mistakes
Watch for these common mistakes:
- Treating the AED as a replacement for 911 or CPR. It works alongside both.
- Locking it away. A cabinet no one can open after hours does not help [11].
- Ignoring chirps or expired dates. A chirp or warning light means the device needs attention.
- Leaving it in a hot or frozen vehicle. Follow the temperature range in your manual.
- Forgetting to restock. A used AED with no fresh pads is out of service.
- Keeping EMS in the dark. If dispatchers do not know you carry an AED, they cannot send you.
Frequently asked questions
Can I hurt someone by using an AED?
An AED shocks only when it finds a rhythm that a shock can treat [3]. In the large public access trial, trained volunteers gave no inappropriate shocks [6]. The bigger risk is waiting, because every minute without CPR or a shock lowers the chance of survival [5].
Do I need a certificate to use an AED in an emergency?
AEDs are built to be easy to use, so a person with no medical background can follow the prompts [2]. Federal law protects people who use one in good faith, except for gross negligence or willful misconduct [14]. Training still makes you faster and calmer.
Can an AED be used on a child?
Yes. CDC estimates about 23,000 cardiac arrests in children each year [1]. Red Cross adult steps apply to children 8 and older who weigh more than 55 pounds [10]. Many AEDs offer child pads or a child key [4], and a class that covers children teaches the differences.
Is it safe to use an AED in the rain or on a wet road?
Wipe the person’s chest dry before placing the pads, as AED steps direct [10]. If you can do so safely, move the person out of standing water. Make sure no one touches the person when the AED checks the rhythm or shocks [10]. Follow your device’s instructions for wet conditions.
Will an AED help someone injured in a car accident?
It depends on why the heart stopped. Cardiac arrests from crash injuries have low survival, while those with a medical cause do better [7]. Some drivers have a heart emergency first and then a collision [7]. If the person is unresponsive and not breathing normally, use the AED. It will decide whether a shock can help [3].
The bottom line
Recommendation from Safety Behind the Wheel Foundation
Safety Behind the Wheel Foundation encourages every fleet and responder agency to keep a ready AED within reach of its crews. An AED lets an ordinary person give the shock that some cardiac arrests need, but only if it is close, charged and in trained hands. For responders, road crews, fleets and transit sites, the plan is the same. Pick a simple, approved model, mount it where the crew can reach it, check it every shift and practice until the steps feel automatic.
Tell your local EMS agency where your AEDs are, and learn your state’s rules before you buy. Those steps can turn minutes of waiting into a real chance at survival.
Related articles
Sources and further reading
- 1Centers for Disease Control and Prevention. Cardiac Emergency Response Plans. Updated September 9, 2026. Data year: not stated (current estimates). cdc.gov/…/index.html
- 2American Red Cross. What is an AED? Accessed October 2026. Data year: not stated (annual estimate). redcross.org/…/what-is-aed
- 3U.S. Department of Health and Human Services and General Services Administration. Guidelines for Public Access Defibrillation Programs in Federal Facilities. Federal Register, 66 FR 28495, May 23, 2001. govinfo.gov/…/01-12939.htm
- 4Electronic Code of Federal Regulations. 21 CFR 870.5310, Automated external defibrillator system. Up to date as of September 22, 2026. ecfr.gov/…/section-870.5310
- 5Occupational Safety and Health Administration. Automated External Defibrillators (AEDs): Overview. Accessed October 2026. osha.gov/aed
- 6Hallstrom AP, et al. Public-access defibrillation and survival after out-of-hospital cardiac arrest. New England Journal of Medicine, 2004;351(7):637-646. Data year: trial data collected before 2004. pubmed.ncbi.nlm.nih.gov/15306665
- 7Sado J, et al. Characteristics and Outcomes of Out-of-Hospital Cardiac Arrest Occurring While in a Motor Vehicle. American Journal of Cardiology, 2018;121(11):1387-1392. Data year: 2009 to 2015. pubmed.ncbi.nlm.nih.gov/29605079
- 8Husain S, Eisenberg M. Police AED programs: a systematic review and meta-analysis. Resuscitation, 2013;84(9):1184-1191. Data year: studies published through 2012. pubmed.ncbi.nlm.nih.gov/23643893
- 9Washington State Legislature. RCW 70.54.310, Semiautomatic external defibrillator, duty of acquirer, immunity from civil liability. Enacted 1998 (1998 c 150 s 1). app.leg.wa.gov/RCW/default.aspx?cite=70.54.310
- 10American Red Cross. AED Steps: How to Use an AED Correctly. Accessed October 2026. redcross.org/…/aed-steps
- 11Smith TM, et al. Automated External Defibrillator Availability, Accessibility, and Usability in High-Risk Out-of-Hospital Cardiac Arrest Neighborhoods of Birmingham, Alabama. Circulation: Population Health and Outcomes, published September 2026. Data year: 2025. pubmed.ncbi.nlm.nih.gov/42695142
- 12New York State Senate. New York Public Health Law Section 3000-B, Automated external defibrillators; public access providers. Text as shown on site, revised June 2026. nysenate.gov/legislation/laws/PBH/3000-B
- 13Adriansen DJ, Fischberg BL, Marill KA, et al. A Heterogeneous Legal Landscape Governs Community AED Use: Crowdsourced United States AED Legal Review and Gap Analysis. Prehospital Emergency Care, 2025;30(2):258-268. Data year: laws in force at time of review (published 2025). pubmed.ncbi.nlm.nih.gov/40257330
- 14Office of the Law Revision Counsel, U.S. House of Representatives. 42 U.S.C. 238q, Liability regarding emergency use of automated external defibrillators. Accessed October 2026. uscode.house.gov/…/view.xhtml?req=granuleid:USC-prelim-ti…
- 15Florida Legislature. Florida Statutes Section 401.2915, Automated external defibrillators. Last amended by ch. 2012-177. leg.state.fl.us/…/0401.2915.html
This article reflects the safety priorities of cardiac arrest response on the road and at work. It is general education, not medical, legal or financial advice, and it does not replace a CPR and AED class. AED laws change, so verify details with official sources. For your own situation, contact your state EMS office or health department, your local EMS agency, your program's medical director or your doctor. Reviewed October 2026.
Cite this article: Safety Behind the Wheel Foundation. “Automated external defibrillators (AEDs): how they work, vehicle use, training and upkeep.” drivewithcare.org, https://drivewithcare.org/automated-external-defibrillator-aed-vehicles/. Reviewed October 2026.
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