An Automated External Defibrillator (AED) is a life-saving device used in sudden cardiac arrest emergencies. The readiness of an AED is determined not by a single expiration date but by the separate lifespans of three distinct components. The device’s ability to function relies on the main unit’s hardware integrity, the battery’s power capacity, and the electrode pads’ chemical stability. Understanding these individual expiration and replacement cycles is essential for ensuring the device is ready to deliver a therapeutic shock.
The Lifespan of the Main Unit
The AED main unit, which contains the electronics and housing, does not have a hard expiration date. Its longevity is typically defined by the manufacturer’s warranty period, which commonly ranges from five to ten years and covers defects in materials or workmanship.
The internal electronics are often designed to function for ten to fifteen years with proper care and maintenance. The main unit’s lifespan depends heavily on being stored under recommended conditions and avoiding physical damage. Exposure to extreme temperatures or humidity can compromise the sensitive circuitry and housing, potentially shortening its operational life. The unit remains functional as long as it passes its self-tests and replacement parts, such as batteries and pads, are available.
Battery Longevity and Replacement Cycles
Battery failure is the most frequent cause of an AED being non-functional. Battery life is measured by two separate metrics: shelf life and standby life. Shelf life refers to how long a battery lasts when stored unused in its original packaging, typically spanning five to seven years from the date of manufacture.
Standby life is the period the battery remains capable of delivering a shock while installed in the AED, which is a significantly shorter span of two to five years. This difference exists because the installed battery continuously powers the AED’s internal monitoring system and periodic self-tests, gradually draining the charge. Most AEDs use disposable lithium batteries that must be replaced after expiration or a rescue. Conversely, some models utilize rechargeable batteries, which require regular charging and more frequent replacement compared to their disposable counterparts.
Electrode Pad Expiration
Electrode pads are a consumable component with a definite expiration date that must be monitored closely. The typical shelf life for AED pads is between 18 months and 5 years, with most models falling in the two to four-year range. This expiration results from the breakdown of the conductive gel coating the adhesive side of the pads.
The gel is necessary to ensure strong adhesion to the patient’s skin and to facilitate the efficient transfer of electrical current from the AED to the heart. Over time, the water-based electrolyte gel dries out, reducing both the pads’ ability to stick and their conductivity. Using expired pads risks poor electrical contact, which can compromise the device’s analysis of the heart rhythm and decrease the effectiveness of the delivered shock. Manufacturers produce different sized adult and pediatric pads, and having both on hand is necessary for comprehensive readiness.
Essential Readiness Checks
Ensuring an AED lasts its intended lifespan requires a proactive maintenance routine focused on operational status and environmental control. Most AEDs perform automatic self-checks daily or weekly, communicating results via a small visual indicator light. A green or solid indicator signals the device is rescue-ready, while a flashing or red light, or an audible chirping sound, alerts the user to a detected problem.
These visual checks should be performed routinely to confirm the ready status and that the device is accessible. The storage environment significantly impacts the longevity of all components. Extreme heat accelerates the degradation of the battery’s lithium chemistry and causes the conductive gel on the pads to dry out prematurely. Similarly, freezing temperatures can quickly drain battery capacity and prevent proper pad adhesion.
AED manufacturers typically specify an optimal temperature range for storage and operation, generally between 32°F and 122°F. Storing the AED in a climate-controlled location, away from direct sunlight, is the most effective way to maximize the lifespan of the battery and pads. When an issue is identified by the status indicator, the user must check the expiration dates on the installed battery and electrode pads, as timely replacement restores the device to operational status.