What Is a Defibrillator? Types, How AEDs Work & Workplace Guide

Reviewed by Prabakar Mahalingam, Managing Partner at AED Total Solution. Prabakar is a renowned national provider of safety training, products, and proprietary compliance software dedicated to addressing Sudden Cardiac Arrest (SCA).

Every year, more than 356,000 out-of-hospital cardiac arrests occur in the United States, according to the American Heart Association (AHA). For roughly 10,000 of those incidents, the victim is at work. Survival depends on how quickly someone intervenes, and a defibrillator is the single most effective tool for restoring a normal heart rhythm during sudden cardiac arrest.

This guide explains what a defibrillator is, how it works, the four main types of defibrillators, and why having an AED in your workplace can be the difference between life and death.

What Is a Defibrillator?

A defibrillator is a medical device that delivers a controlled electrical shock to the heart. Its purpose is to interrupt a dangerously abnormal heart rhythm, such as ventricular fibrillation or pulseless ventricular tachycardia, and allow the heart to re-establish a normal, effective beat.

During sudden cardiac arrest, the heart’s electrical system malfunctions. Instead of contracting in a coordinated rhythm, the heart quivers or stops pumping blood entirely. Without intervention, the brain and vital organs begin to suffer irreversible damage within minutes. A defibrillator resets the heart’s electrical activity so it can resume pumping blood.

Defibrillators come in several forms. Some are portable devices designed for use by everyday bystanders, while others are surgically implanted inside a patient’s body. The type most commonly found in workplaces, schools, and public spaces is the automated external defibrillator (AED).

How Does a Defibrillator Work?

A defibrillator works by sending an electrical pulse through the chest and into the heart muscle. This pulse momentarily stops all electrical activity in the heart, giving it the opportunity to restart with a normal rhythm. Think of it as a “reset button” for the heart’s electrical system.

Here is what happens step by step during defibrillation:

1. Detection: The device analyzes the heart’s rhythm through electrode pads placed on the patient’s bare chest. Modern defibrillators use sophisticated algorithms to determine whether a shockable rhythm is present.
2. Charging: If the device detects ventricular fibrillation or pulseless ventricular tachycardia, it charges its internal capacitor to the appropriate energy level.
3. Shock delivery: The electrical shock is delivered through the electrode pads. Most modern devices use biphasic waveform technology, which the AHA recognizes as more effective and safer than older monophasic systems.
4. Reassessment: After the shock, the device re-analyzes the heart rhythm. If a normal rhythm has not been restored, the cycle may repeat. CPR should continue between shock cycles.

The entire process takes only seconds. When paired with cardiopulmonary resuscitation (CPR), early defibrillation can double or triple a cardiac arrest victim’s chance of survival, according to the AHA.

Types of Defibrillators: AED vs. Manual vs. ICD vs. WCD

There are four main types of defibrillators, each designed for different situations and users. Understanding the differences helps organizations choose the right solution for their environment.

1. Automated External Defibrillator (AED)

An AED is a lightweight, portable device designed for use by the general public. It automatically analyzes the heart’s rhythm and determines whether a shock is needed. AEDs guide the user through each step with voice prompts, visual instructions, or both.

Key characteristics of AEDs:

• Designed for use by non-medical personnel with minimal or no training
• Portable and battery-operated
• Available in semi-automatic (user presses a button to deliver the shock) and fully automatic models
• Built-in safeguards prevent a shock from being delivered unless a shockable rhythm is detected
• Found in workplaces, schools, airports, gyms, government buildings, and other public locations
• All AEDs used in the U.S. must be FDA-approved

AEDs are the type of defibrillator most relevant to workplace safety and organizational preparedness. If you are evaluating AED devices for your organization, explore our selection of FDA-approved AEDs.

2. Manual External Defibrillator

Manual defibrillators are used by trained medical professionals in hospitals, ambulances, and advanced life support settings. Unlike AEDs, manual defibrillators require the operator to interpret the heart rhythm, select the energy level, and decide when to deliver the shock.

Key characteristics:

• Require advanced medical training (ACLS certification)
• Allow full control over energy levels and timing
• Often include additional monitoring capabilities (ECG, SpO2, blood pressure)
• Used in emergency rooms, operating rooms, and ambulances

Manual defibrillators are not appropriate for public-access or workplace use because they require clinical expertise to operate.

3. Implantable Cardioverter Defibrillator (ICD)

An ICD is a small device surgically implanted under the skin, typically in the upper chest. It continuously monitors the heart’s rhythm and automatically delivers a shock if it detects a life-threatening arrhythmia.

Key characteristics:

• Implanted through a surgical procedure
• Provides continuous, 24/7 heart rhythm monitoring
• Delivers internal shocks automatically when needed
• Used for patients with a high risk of sudden cardiac arrest due to existing heart conditions (learn more about life expectancy after ICD implant)
• Available in transvenous, subcutaneous, and cardiac resynchronization therapy (CRT-D) configurations

4. Wearable Cardioverter Defibrillator (WCD)

A WCD is a vest-like device worn on the outside of the body, under clothing. It continuously monitors the heart and can deliver a shock if it detects a dangerous rhythm. WCDs serve as a temporary solution for patients who need defibrillator protection but are not yet candidates for an ICD.

Key characteristics:

• Worn externally, no surgery required
• Provides continuous monitoring similar to an ICD
• Typically prescribed as a bridge therapy
• Used while a patient is awaiting ICD implantation or during recovery from a cardiac event

What Does AED Stand For?

AED stands for Automated External Defibrillator. For details, see our guide on what AED stands for. The name describes exactly what the device does:

• Automated: The device automatically analyzes the heart rhythm and determines whether a shock is needed. Some models deliver the shock automatically; others prompt the user to press a button.
• External: The device is applied to the outside of the body using adhesive electrode pads placed on the chest. No surgery or invasive procedure is involved.
• Defibrillator: The device can deliver an electrical shock (defibrillation) to restore a normal heart rhythm.

The critical distinction between an AED and other defibrillators is accessibility. AEDs are specifically designed so that anyone can use them, regardless of medical background. According to the FDA, public-access AEDs “are intended to be used by laypeople who have received minimal training.” The AHA echoes this guidance, noting that although formal training is recommended, it is not required to use an AED.

For a detailed walkthrough of using an AED in an emergency, see our step-by-step guide on how to use an AED.

Who Can Use an AED?

The short answer: anyone. AEDs are designed to be used by the general public, including people with no medical training. The device provides clear voice prompts and visual instructions to guide the user through every step.

Important safety facts about AED use:

• You cannot harm someone by using an AED. The device will only deliver a shock if it detects a shockable heart rhythm. If the heart is beating normally, the AED will not deliver a shock.
• Legal protections exist. The federal Cardiac Arrest Survival Act of 2000, along with Good Samaritan laws in all 50 states and the District of Columbia, provides limited immunity from civil liability for people who use an AED in good faith during an emergency.
• Training is recommended but not required. The AHA recommends AED and CPR training to build confidence, but formal certification is not a legal prerequisite for using an AED on someone in cardiac arrest.

If your organization wants to prepare employees to respond confidently in an emergency, consider pairing your AED program with training. Learn more about AED certification requirements and training options.

Why Your Workplace Needs an AED

Sudden cardiac arrest does not discriminate by age, fitness level, or occupation. It can strike anyone, anywhere, at any time. Workplaces that are equipped with AEDs and trained responders give their employees the best possible chance of survival.

The Numbers Make the Case

• ~10,000 cardiac arrests per year occur in workplace settings, according to OSHA.
• Cardiac arrest accounts for 13% of all workplace fatalities.
• Survival drops 7-10% for every minute without CPR or defibrillation (AHA).
• 90% survival rate when defibrillation is delivered within the first minute.
• Only 5-7% survival when organizations rely solely on EMS response times (OSHA).
• Up to 60% of workplace cardiac arrest fatalities might have been prevented if AEDs were immediately available (OHS Online).
• Workplace cardiac arrests show up to 5.9 times higher survival rates compared to other settings when AED programs are in place.

OSHA and Regulatory Guidance

While there is no federal mandate requiring AEDs in every workplace, OSHA strongly recommends them as part of a comprehensive first-aid response plan. OSHA’s guidelines state that employers must ensure adequate first-aid treatment is available, either through trained personnel or rapid access to emergency services. For many workplaces, especially those with remote locations or large footprints, having on-site AEDs is the most practical way to meet this standard.

Additionally, many states have enacted their own AED requirements for specific industries and building types, including schools, fitness centers, and government buildings. Requirements vary by state. For an overview of state-specific regulations, see our guide to AED state law compliance.

Beyond Compliance: Duty of Care

Having an AED program demonstrates that your organization takes its duty of care seriously. It reduces liability exposure, may lower insurance premiums, and most importantly, shows employees that their safety is a priority. An AED program is not just equipment on a wall. It is a system of readiness that includes device placement, regular inspections, maintenance, documentation, and trained responders. For guidance on optimal device positioning, see our AED placement guidelines and compliance overview.

Managing all of these components can be complex, especially for organizations with multiple locations. That is where a managed AED program comes in. Learn how AED Total Solution’s program management services can handle every aspect of AED compliance and readiness for your organization.

How to Choose the Right AED for Your Organization

Selecting an AED involves more than picking a device off a shelf. The right choice depends on your environment, the size of your facility, and your compliance obligations. Here are the key factors to consider:

1. FDA approval: Only purchase FDA-approved AED devices. The FDA maintains a public list of approved devices and accessories.
2. Ease of use: Look for clear voice prompts, visual guides, and intuitive design. Semi-automatic models require a button press to deliver a shock; fully automatic models deliver the shock on their own.
3. Durability and environment: Consider whether the AED will be used indoors, outdoors, or in extreme conditions. Some models are designed for harsh environments such as construction sites or manufacturing floors.
4. Pad and battery lifecycle: AED pads and batteries have expiration dates. Choose models with long shelf lives and set up a system to track and replace consumables before they expire.
5. Pediatric capability: If your organization serves children (schools, daycares, recreation centers), ensure the AED supports pediatric pads or has a pediatric mode.
6. Ongoing maintenance and monitoring: AEDs require regular inspections, firmware updates, and documentation to remain compliance-ready. A managed AED program ensures nothing falls through the cracks.
7. Multi-location scalability: Organizations with multiple sites need centralized visibility into the status of every device. Look for solutions that provide dashboards, automated alerts, and audit-ready reporting.

Need help selecting the right AED solution? Contact AED Total Solution for a personalized recommendation based on your organization’s size, industry, and compliance needs.

For organizations that need AEDs for a limited time, such as events or construction projects, our AED rental program provides a flexible alternative to purchasing.

Frequently Asked Questions About Defibrillators

What is the difference between an AED and a defibrillator?

An AED is a type of defibrillator. The term “defibrillator” refers to any device that delivers an electrical shock to the heart. AEDs are the portable, user-friendly version designed for non-medical personnel. Other types of defibrillators include manual devices used by paramedics and doctors, implantable cardioverter defibrillators (ICDs) placed inside the body, and wearable cardioverter defibrillators (WCDs).

Can you use a defibrillator on someone with a pacemaker?

Yes. According to the AHA, a defibrillator can be used on someone who has a pacemaker or an ICD. For details, see our guide on how defibrillators differ from pacemakers. The key precaution is to avoid placing the electrode pads directly over the implanted device. Most AED instructions address pad placement clearly.

Do you need training to use an AED?

Formal training is not legally required. AEDs are designed for use by anyone, with step-by-step voice and visual instructions. However, the AHA and the American Red Cross both recommend CPR and AED training to improve confidence and response time. Many organizations include AED training as part of their workplace safety programs.

How much does an AED cost?

AED prices vary depending on the manufacturer, features, and accessories included. Beyond the initial purchase price, organizations should account for ongoing costs such as replacement pads, batteries, and program management. For organizations that want a full-service solution, AED Total Solution offers comprehensive program management that covers device maintenance, inspections, compliance tracking, and documentation.

Are AEDs required by law in workplaces?

There is no single federal law requiring AEDs in all workplaces. However, OSHA recommends them as part of workplace first-aid preparedness. Many states have enacted their own AED requirements for specific settings, including schools, fitness centers, government buildings, and certain commercial facilities. Requirements vary by state, so it is important to understand the regulations that apply to your location and industry.

How often should AEDs be inspected?

The FDA recommends routine maintenance checks to ensure AEDs are ready for use. Most manufacturers recommend monthly visual inspections and periodic functional tests. Pads and batteries must be replaced before their expiration dates. Organizations should maintain a documented inspection schedule. A managed AED program automates inspection tracking, sends compliance reminders, and maintains audit-ready records. Learn more about AED pad maintenance and placement.

What should I do if someone goes into cardiac arrest at work?

Follow the DRSABCD action plan: check for Danger, check for Response, Send for help (call 911), open the Airway, check for Breathing, begin CPR, and use a Defibrillator (AED) as soon as one is available. The AED will guide you through each step. Continue CPR between shocks until emergency medical services arrive.

Protect Your People with a Response-Ready AED Program

A defibrillator is not just a piece of equipment. It is the most time-critical tool in any cardiac emergency. Understanding the types of defibrillators, how they work, and why AEDs belong in your workplace is the first step toward building a safer environment for everyone.

AED Total Solution provides full-service AED program management that covers everything from device selection and placement to ongoing inspections, compliance tracking, remote monitoring, and audit-ready documentation. We combine software-driven monitoring with hands-on program oversight so your AEDs are not just present, but truly ready when every second counts.

Ready to strengthen your organization’s emergency preparedness? Explore our AED program management services or browse FDA-approved AED devices to get started.