Checking an AED takes about two minutes and involves verifying the status light, confirming that electrode pads haven’t expired, and making sure the battery still has life. Most organizations should do this monthly, though a quick visual check of the status indicator can happen anytime you walk past the unit. A study published in JAMA found that maintenance errors and neglected equipment checks account for a large share of defibrillator failures during actual emergencies, so these simple inspections genuinely matter.
Check the Status Indicator Light
Every AED has a status indicator, usually a small light on the front or top of the device. When the light flashes green, the unit is operational and ready to use. A red, orange, or non-flashing light means something is wrong, whether that’s a dead battery, an internal fault, or expired pads the device has detected.
For a more thorough check, open the AED lid. The status indicator should briefly turn red, then return to green within about five seconds. You should also hear voice prompts begin to play, confirming that the speaker works. Close the lid and watch for the same red-to-green cycle again. If the light stays red or the device stays silent, it needs servicing.
The two most common AED models in public spaces are the Philips HeartStart OnSite and the Zoll AED 3. Both use a green flashing light to signal readiness, but the exact location and style of the indicator varies. If you’re responsible for checking an AED, spend a minute with the user manual so you know exactly where to look on your specific model.
Verify Electrode Pad Expiration Dates
Electrode pads have a printed expiration date on their sealed packaging. Expired pads may not conduct electricity properly, and the adhesive gel can dry out over time, meaning they won’t stick to a patient’s chest when it counts. Check this date every month and replace pads shortly before they expire, not after.
A few important rules for pad storage:
- Keep pads sealed. Don’t open the packaging until an actual emergency. The gel begins to dry once exposed to air.
- Watch for temperature damage. Pads exposed to extreme heat or cold, or repeated temperature swings, can degrade faster than the printed date suggests. If your AED sits in a vehicle, an outdoor cabinet, or near a loading dock, inspect pads more frequently.
- Stock the right type. If your location serves children, confirm you have pediatric pads available and that those are current too.
Confirm Battery Life
AED batteries typically last about five years in standby mode, but this varies by manufacturer and how often the device runs self-checks. The expiration or installation date is usually printed on the battery itself or recorded on a sticker on the outside of the unit. Write the install date on the battery with a marker if it isn’t already there.
A passing self-test (green status light) is the easiest way to confirm the battery still holds a charge. Some models display a battery level icon when you open the lid. If the battery is within a few months of its expected end of life, replace it proactively. A device that passes its self-test today could fail next month if the battery is on its last leg.
Inspect the Storage Environment
Most AEDs are rated for storage between 32°F and 122°F (0°C to 50°C). That range covers most indoor environments easily, but outdoor cabinets, parked vehicles, and unheated warehouses can push past those limits in summer or winter. Heat is especially damaging because it accelerates battery drain and degrades the adhesive gel on electrode pads.
During your check, look at the physical condition of the AED and its case. Make sure nothing is cracked, that no moisture has gotten inside, and that all accessories (a razor, gloves, a CPR barrier mask) are still present if your kit includes them.
Test the Wall Cabinet Alarm
If your AED lives in a wall-mounted cabinet with a built-in alarm, that alarm needs its own check. The alarm runs on a 9-volt alkaline battery that lasts roughly two years in standby mode, though replacing it once a year is a safer practice. To test it, make sure both the key switch and the internal alarm switch are in the ON position, then open the cabinet door. You should hear a loud alarm and, if the cabinet has one, see a strobe light flash.
A low alarm battery can cause partial failures. The audible alarm might still sound when the door opens, but the strobe light won’t flash. If you hear a periodic “chirp” coming from the cabinet, that’s the alarm telling you its battery is dying and needs immediate replacement. Most cabinets also have a key switch on the outside that lets you silence the alarm during routine maintenance so you don’t cause a scene every time you do an inspection.
Keep a Written Log
A simple paper log stored near the AED, or a digital spreadsheet, creates accountability. Each monthly entry should record the date, the inspector’s name, the status light result, the pad expiration date, and the battery expiration date. This log does two things: it proves to regulators or your organization that the device is being maintained, and it creates a pattern you can spot over time. If a device starts failing its self-test intermittently, a log makes that visible before a real emergency exposes the problem.
Many workplaces assign AED checks to front-desk staff, security teams, or facilities personnel. What matters less is who does it and more that someone specific is responsible, with a backup if that person is out. Research on defibrillator failures consistently points to the same issue: not that the technology is unreliable, but that no one was clearly assigned to keep it ready.