How Many AEDs Does My Building Need? A Practical AED Placement & Coverage Guide

The most common compliance mistake. A facility installs one AED near reception, checks the “we have an AED” box, and assumes it’s done. In a 25,000 sq ft single-floor open office, that may genuinely be enough. In a multi-floor school, a sprawling warehouse, or a hotel with locked guest corridors, one centrally-mounted device covers a small fraction of the building inside the 3-minute window.

How AED Quantity Planning Actually Works

AED quantity is not driven by square footage alone, contrary to what most “1 AED per X sq ft” rules of thumb suggest. It’s driven by response time, with square footage as a proxy. The relationship is simple once you break it down:

1. Total drop-to-shock budget   = 180 seconds (the 3-min rule)
2. Subtract setup + shock time  = ~60 seconds (open AED, place pads, analyze, shock)
3. Round-trip walking budget    = 120 seconds
4. One-way walking time         = 60 seconds

5. Average pedestrian speed     = 4.4 ft/s (FHWA standard)
6. Straight-line one-way reach  = 60 × 4.4 = 264 ft

7. Real-walk distance           = 264 ÷ building path factor
8. Effective coverage radius    = result of step 7
9. Coverage area per AED        = π × radius²

10. Safety factor applied       = ÷ 1.85 (industry convention)

The path factor reflects how circuitous a real building is compared to a straight line. A warehouse aisle is nearly straight (path factor ~1.2). A partitioned office with hallways and doors forces detours (~2.0). A hospital with security wings and locked stairwells is brutal (~2.5). The same square footage covers a vastly different number of people depending on which layout you’re working in.

Then there’s the floor problem. Every floor needs its own AED, full stop. Stairs and elevators add 60 to 90 seconds to retrieval time, which mathematically eliminates the possibility of meeting the 3-minute rule across floors. There is no clever placement that solves this. Plan for one device per occupied floor as a hard minimum.

AED Coverage by Building Type, in Plain English

Different facilities have different coverage densities, not because the AHA rule changes, but because the path factor and the risk profile change. Here are the typical sq-ft-per-AED values once the math is applied:

Notice the gym number. The math alone would suggest ~30,000 sq ft per AED, similar to a partitioned office. But cardiac arrest is significantly more likely during vigorous exertion, NEJM 2000 (Albert CM et al.) documented up to 17× higher risk in habitually inactive individuals during exercise. The coverage tightens because the underlying risk is higher, not because the building is harder to walk.

How the AED Quantity Calculator Works

The AED Quantity Calculator automates the math above. You provide three to five inputs and the tool returns a defensible number based on the AHA 3-minute rule.

Building type sets the sq-ft-per-AED baseline and the path factor automatically. Total square footage drives the coverage-by-area calculation. Number of floors sets a hard minimum (one AED per floor), independent of square footage. High-risk areas (gym zones, pools, kitchens, heavy machinery) apply a 1.3× risk multiplier to the recommended count. Optional locked-zone inputs add one device per separately access-controlled area.

The calculator returns two numbers: a bare minimum that satisfies most state compliance baselines, and a recommended count that meets the AHA 3-minute drop-to-shock standard. The gap between the two is where survival outcomes live.

Real-World Coverage Examples

The math comes alive when applied to actual buildings. These are typical outputs the calculator produces for common facility sizes:

The Most Common AED Placement Mistakes

Coverage math is only half the battle. The other half is where you actually mount each device. After reviewing hundreds of real facility AED programs, the same placement mistakes appear over and over:

1. Treating multiple floors as one zone

The most common, most expensive mistake. A facility installs one AED on the ground floor and assumes it covers the second and third floors. It doesn’t. Plan one AED per occupied floor minimum, more if a floor exceeds the building-type sq-ft-per-AED threshold.

2. Mounting AEDs in locked offices or back rooms

If the AED is behind a locked door after hours, it covers nobody after hours. Mount in public-access corridors, alarmed cabinets, and visible locations. The American Red Cross and OSHA guidance both emphasize unrestricted access during all operating hours.

3. Poor or missing signage

A bystander who can’t see the device in a panic cannot retrieve it in 3 minutes. Standardized AED signage with the universal heart-and-bolt symbol, visible from at least 50 feet, mounted at the device location and at every floor entrance.

4. Distance from likely incident zones

In a gym, the AED belongs on the floor, near the cardio equipment, not in the manager’s office. In a manufacturing plant, near production lines, not the break room. Place devices where cardiac events are statistically most likely to occur.

5. Failing to register and maintain

Most U.S. states require AED registration with the local EMS authority. Pads expire every 2 years, batteries every 3 to 5. A device with expired consumables is not coverage, it’s a liability. Monthly visual inspection and an annual deeper check are the baseline maintenance routine.

Minimum Compliance vs AHA Recommendation: The Critical Gap

Two different numbers come out of every coverage analysis, and the gap between them is the single most important detail buyers miss.

Bare minimum compliance is the floor most state laws and insurance policies accept. For many smaller buildings, that’s one AED, sometimes regardless of layout. It satisfies the statute. It does not guarantee the building meets the 3-minute survival standard.

AHA recommended coverage is what the science says you actually need to meet the survival math, every point in the building reachable within a 3-minute drop-to-shock round trip. It’s not legally required in most jurisdictions. It is what separates a compliant building from one where collapse is genuinely survivable.

The gap, often one or two extra devices and a few thousand dollars over five years, translates roughly into a 50-percentage-point survival difference (70% with timely defibrillation vs 20% without). For schools, healthcare, public-access venues, and any facility where wrongful-death liability is non-trivial, the AHA-aligned number is the only defensible answer. The minimum compliance number is the one buyers regret.

What if my building’s layout doesn’t fit a standard building type?

Most real buildings are hybrids. Use the closest match in the calculator and override with the longest-walk-distance input if you have a known farthest point greater than 250 feet from the proposed AED location. When in doubt, consult your medical director or local EMS authority.

The Bottom Line

AED quantity is not a guess. It’s a response-time problem with a defensible answer. Apply the AHA 3-minute rule, multiply by your building’s path factor, add one device per floor, layer in risk modifiers for gyms and machinery, and you have a number that holds up to legal, insurance, and clinical scrutiny.

Run your building through the AED Quantity Calculator to confirm the number. Use the Find Your Perfect AED tool to choose the right model for each location. Model the full 5-year cost with the AED Cost Calculator before procurement. Register with your local EMS authority. Train at least one designated responder per location. Inspect monthly. That’s the entire program, distilled into a paragraph.