How Many AEDs Are Required in a Building?

No universal code tells you to install exactly three or seven AEDs in a building. The number depends on how quickly someone anywhere inside can reach a device, and the target that drives every major guideline is getting a shock delivered within three to five minutes of a cardiac arrest. In practice, that means placing AEDs so that the farthest occupant is no more than about a 90-second walk from one. A small single-story office might need just one; a sprawling multi-floor complex could need a dozen or more. The real question is not “how many” but “how far,” and that distinction changes how you think about placement entirely.

Why Every Minute Matters

The number of AEDs a building needs is ultimately a question about time, so the survival data behind the time targets are worth understanding. In a study of over 3,700 patients with witnessed out-of-hospital cardiac arrest, the chance of a shock successfully stopping a lethal heart rhythm dropped from 93% when the shock arrived within six minutes to 75% when it took longer than 16 minutes. Each additional minute of delay was associated with roughly a 6% drop in the chance of surviving to hospital discharge.¹ Separate modeling from Canadian communities estimated that cutting the response interval from eight minutes down to five could save dozens of additional lives per year in medium-sized cities.²

When a bystander applies an AED before paramedics arrive, the survival advantage is striking. A large analysis across a population of 21 million found that overall survival to hospital discharge was 7%. Among those who received bystander CPR alone, survival was 9%. When someone applied an AED before emergency services arrived, it rose to 24%, and when the AED delivered a shock, survival reached 38%.³ Those numbers explain why guidelines focus so heavily on having AEDs reachable before professional responders can possibly get there. An ambulance stuck in traffic or an elevator is irrelevant if a device is already on the floor where someone collapsed.

The 90-Second Walk Rule

The most widely cited placement principle comes from the American College of Sports Medicine, though its logic applies far beyond gyms. The recommended target is a total response time of three minutes (optimal) to five minutes (acceptable) from collapse to first shock. Because someone has to notice the arrest, call for help, run to the AED, grab it, return, and apply it, the device itself should be reachable within about a 90-second walk from any point in the facility.⁴ That 90 seconds accounts for only half the round trip; the responder still has to get back to the patient.

Translating a 90-second walk into a physical distance is straightforward but depends on the building. In open spaces at a brisk pace, people cover a lot more ground than they do navigating hallways, locked doors, and stairwells. Research tracking real-world lay responders found a median travel speed of about 2.3 meters per second, though this varied widely depending on urban density and obstacles.⁵ At that pace, 90 seconds covers roughly 200 meters in a straight line. But nobody walks in a straight line inside a building. Corridors force detours, locked security doors create chokepoints, and stairs slow you down. A reasonable planning rule for indoor environments is that each AED covers a radius of about 100 meters of actual walking distance, though building managers should walk the routes themselves with a stopwatch to verify.

From there, the math becomes building-specific. A rectangular single-floor office that measures 50 meters long can probably be covered by one centrally placed AED. An L-shaped building of the same total square footage might need two because the walking route around the corner doubles the effective distance. A campus-style facility with detached wings will need one per wing regardless of total area.

Multi-Floor Buildings and High-Rises

Adding floors changes the calculation dramatically. Cardiac arrests on higher floors of residential buildings already carry worse outcomes than those at ground level. A study from Toronto found that the delay between first responders arriving at the building entrance and actually reaching the patient was nearly five minutes on higher floors compared with three minutes at ground level. Arrests on the third floor or above were independently associated with about a 30% lower chance of survival to discharge.⁶ Those delays come from waiting for elevators, navigating fire doors, and simply covering vertical distance with heavy equipment.

For building managers, the implication is that a single lobby AED is almost never sufficient in a multi-story building. The ACSM guideline explicitly recommends placing an AED on each floor of multi-floor facilities.⁴ In tall buildings, even that may not be enough if a single floor is very large.

Researchers have also modeled whether it makes more sense to keep AEDs in building lobbies or in elevators. The answer depends on the building’s height and the relative likelihood of cardiac arrest on different floors. In a building where cardiac-arrest risk is roughly equal on every floor, placing an AED in the elevator produced shorter average response distances. A lobby-based AED performed better only in shorter buildings where ground-floor risk was much higher than upper-floor risk.⁷ This is largely theoretical, since keeping a device in a moving elevator raises practical questions about what happens when the elevator is on the wrong floor. But it illustrates the point that vertical travel is the dominant bottleneck in tall buildings, and any placement strategy that ignores it is incomplete.

Venues That Need Extra Coverage

Not all buildings carry equal cardiac-arrest risk, and high-risk settings justify denser AED placement. Fitness centers and gyms are a prime example. Vigorous exercise can trigger sudden cardiac arrest in people with undiagnosed heart conditions, and the risk is amplified when the clientele skews older or includes people with cardiovascular disease.⁸ In these settings, the three-minute target for collapse to shock is especially important, and many fitness-industry guidelines treat AED provision as a baseline expectation rather than an optional extra.

Schools are another high-priority environment. Though cardiac arrest in young students is rare, school campuses host a far wider age range than most people realize: staff members, coaches, parents at sporting events, and elderly visitors all use the grounds. A study of AED programs in U.S. high schools found high survival rates for both student athletes and older non-students who suffered cardiac arrest on school property.⁹ Despite that evidence, only 17 of 50 U.S. states required AEDs in at least some schools as of 2016, and just five of those states offered clear funding for purchases.¹⁰

Other venues that typically warrant multiple AEDs include airports, convention centers, large retail spaces, sports stadiums, and corporate campuses with thousands of workers. The common thread is either a large footprint that makes the 90-second walk impossible from a single unit, a high density of occupants that raises the baseline probability of an event, or a population profile that tilts toward higher-risk individuals.

Why Having an AED Is Not the Same as Having a Usable AED

One of the most underappreciated problems in AED planning is that devices installed on walls may be invisible or misunderstood in an emergency. The internationally standardized AED sign, a green-and-white symbol following ISO standards, turns out to be poorly recognized by the public. An international survey found that only about one in five people could correctly identify the standard sign, and only about one in four understood it as marking the location of an AED. Most respondents thought the sign indicated first-aid equipment generally, and many confused it with other green “safe condition” signs like emergency exits.¹¹

This matters more than it might seem. In a chaotic emergency, nobody is calmly scanning hallway signs. If the device blends into a wall of safety placards, bystanders may not realize a defibrillator is five meters from where someone just collapsed. A study of public-access defibrillation in Shanghai reinforced this finding at the system level, identifying non-standard signage, restricted access to the venues where AEDs were housed, and fragmented digital platforms as major barriers to getting devices to patients in time.¹² The lesson for building managers is that the number of AEDs you install is only as meaningful as people’s ability to find and access them under stress. Clear, prominent, distinctive signage and unlocked, well-lit cabinets are non-negotiable.

Maintenance Turns “Enough” Into “Not Enough”

A device with a dead battery or expired electrode pads is functionally equivalent to no device at all, and the problem is more common than most organizations realize. A Dutch study that inspected over 200 registered AEDs found that roughly one in five was not functional. The most common reasons were expired electrodes, physical obstacles blocking retrieval, and failed self-tests.¹³ A Japanese study tracking AED maintenance over five years found that about 15% of public AEDs were not ready to use, with invalid electrodes accounting for the majority of failures.¹⁴

A smaller but more recent audit in Birmingham, Alabama, found better numbers, with about 95% of inspected AEDs in usable condition, though roughly one in seven was classified as “at risk” of failure due to approaching expiration dates or minor issues.¹⁵ The variation between studies highlights that maintenance quality is driven by local ownership and accountability. AEDs installed in response to a building code or a one-time corporate initiative tend to be forgotten once the person who championed them moves on. Any serious AED plan includes a maintenance schedule: checking indicator lights monthly, replacing pads and batteries before they expire, and assigning a specific person as the responsible party.

If you are calculating how many AEDs a building needs and your maintenance track record is uncertain, it is worth building in some redundancy. Having a spare device in a central location ensures coverage is not wiped out when one unit fails its self-test on the day someone needs it.

Onsite AEDs Versus Waiting for Paramedics

A common objection to buying multiple AEDs is that emergency services carry their own defibrillators. The data make clear that onsite devices save time the ambulance simply cannot. A study comparing onsite and dispatched AED use found that when a device was already in the building, the median time to first shock was about four minutes. When the AED arrived by dispatch, that time stretched to roughly eight and a half minutes.¹⁶ In a setting where every minute costs about 6% survival, that four-and-a-half-minute gap is the difference between a living patient and a dead one. For buildings in dense urban areas where ambulance response is already fast, onsite AEDs still shave critical minutes off the timeline. For buildings in suburban or rural areas where response times are longer, the case is even more compelling.

Cost-Effectiveness and the Frequency Question

AEDs cost roughly $1,000 to $2,500 per unit, plus ongoing costs for replacement pads and batteries every few years. For a building that needs several, the total investment raises questions about value. Economic modeling has addressed this directly. A cost-effectiveness analysis found that AED deployment cost about $30,000 per quality-adjusted life year when a deployed AED was used on one cardiac arrest every five years. That figure falls well below the commonly used threshold of $50,000 per quality-adjusted life year. The ratio remained favorable as long as the annual probability of use was at least 12%.¹⁷

These numbers mean that in busy public spaces where thousands of people pass through daily, AED placement is cost-effective by almost any health-economics standard. In a small private office with 20 employees, the math is harder to justify on pure probability, though many organizations install AEDs for reasons beyond strict cost-effectiveness: employee peace of mind, risk management, and the moral weight of a life that could be saved. The buildings where the economic case is strongest are those with high foot traffic, aging occupant populations, or physically demanding activities on the premises.

The Regulations Are Patchwork

If you are looking for a specific legal answer to “how many AEDs does my building need,” the honest answer is that it depends entirely on where you are. An international analysis of AED-related legislation found enormous variability across countries, with no global consensus on where devices should be required or how many must be provided.¹⁸ In the United States, requirements vary not just state by state but by building type. Some states mandate AEDs in schools, gyms, or government buildings; others have no requirements at all. Local fire codes, occupancy permits, and industry-specific regulations add further layers.

Because of this patchwork, best practice tends to outrun the law. Many organizations that install AEDs go beyond the minimum legal requirement and follow the guideline-driven approach described above: one unit for every 90-second walking radius, one per floor in multi-story buildings, and extra units in high-risk or high-traffic areas. Meeting only the legal minimum may leave gaps that the survival data clearly show are dangerous.

The Bystander Problem

Even if a building has the right number of well-maintained, clearly signed AEDs in perfect locations, there is one more variable: will someone actually use the device? Bystander AED use remains surprisingly low despite the survival benefits. A narrative review of barriers identified unequal access to CPR training, social hesitations around touching a stranger’s chest, fear of legal consequences, and simply not knowing the device is there as recurring obstacles.¹⁹ Research into the psychological dimensions of the problem found that people who experience high personal distress in emergencies are less willing to perform AED-related actions, while those with greater empathic concern and ability to take others’ perspectives are more willing to act.²⁰

The implication for building managers is that installing AEDs without training is like installing fire extinguishers without fire drills. Regular training sessions, even brief ones that familiarize staff with the device’s location and basic operation, substantially increase the odds that someone will grab the AED and use it when the time comes. Modern AEDs talk the user through every step with audio prompts, so formal certification is not strictly necessary, but confidence matters. A person who has held the device once before is far more likely to use it than someone encountering it for the first time under the worst possible pressure.

Emerging Approaches to Faster Access

The science of AED placement is still evolving. The International Liaison Committee on Resuscitation issued a scientific statement identifying several innovative strategies for getting defibrillators to patients faster, including enhanced public outreach, optimized static deployment models, improved integration with emergency dispatch systems, and exploration of novel delivery methods like drones.²¹ Drone-delivered AEDs are being trialed in several countries, with the idea that a drone can reach a rural or hard-to-access location faster than a person on foot. Inside buildings, newer approaches include smartphone apps that alert nearby trained responders when a cardiac arrest is detected by a 911 call, directing them to the nearest registered AED.

For building-level planning, the most practical near-term development is the growing availability of digital AED registries that link device locations to emergency dispatch centers. When a 911 caller reports a cardiac arrest, the dispatcher can tell them exactly where the nearest AED is. This only works if the building’s devices are registered and kept current in the database, which circles back to the maintenance question. A device that exists in a registry but has expired pads is arguably worse than no listing at all, because it sends a rescuer on a wasted errand during the most critical minutes of someone’s life.