Who Can An AED Be Used On? Every Exception, Answered

Most of the hesitation we hear from safety coordinators is not about whether their people can operate an AED. It is about the moment of doubt in front of an actual patient. She is pregnant. He has a scar and a hard lump under the collarbone. The floor is wet. There is a patch on his chest. Somebody in the room says wait.

That pause is the problem this article exists to remove. Below is every scenario responders ask about, with the answer up front and the reasoning underneath.

The Complete Exception Table

Why The Device Makes Most Of This Decision For You

An AED is not a shock button. It is a rhythm analyzer with a shock button attached. Once the pads are on the chest, the unit reads the electrical activity of the heart and classifies it. If it does not find ventricular fibrillation or pulseless ventricular tachycardia, it announces no shock advised and will not charge. The American Red Cross puts it plainly: a person who is not in cardiac arrest will not receive a shock.

This is the single most useful thing a lay responder can know, because it inverts the risk. The danger in a cardiac arrest is not that an untrained person attaches an AED to someone who does not need it. The danger is that a trained person hesitates over a question the device would have answered in nine seconds.

The Real Exception: Anything Between The Pad And The Skin

Almost every genuine AED complication comes down to contact. A defibrillation pad works by putting current through the chest along a path it can predict. Anything that breaks the seal or offers a shortcut changes that path.

Chest Hair

Dense chest hair holds the pad off the skin. The consequence is not usually a failed shock. It is an impedance reading the device does not like, a check pads prompt, and lost time. Press each pad down firmly with the heel of your hand first. If the unit still reports a pad problem, pull the pads off sharply, which removes much of the hair with them, and apply the spare set. Many AEDs ship with a razor in the response kit for exactly this reason. Shaving is the fallback, not the first move, because it costs seconds you do not have.

Medication Patches

A transdermal patch is the one item on this page that genuinely must come off. Nitroglycerin, fentanyl, nicotine, and hormone patches typically carry a backing that conducts, and a pad placed over one can arc, burn the skin, and divert energy away from the heart. Peel the patch off with a gloved hand, wipe the skin, and place the pad. Do not spend time hunting for patches on the back or arms. You are only concerned with the pad landing zones.

Jewelry And Clothing

Necklaces, chains, and body piercings should be moved out of the pad area rather than removed, which takes too long. Underwire in a bra is not a contraindication. The 2025 American Heart Association guidelines went a step further and addressed this directly, noting it may be reasonable to adjust the position of a bra rather than remove it. That recommendation exists because hesitation over undressing a woman in public measurably delays defibrillation.

The Scenarios That Look Like Exceptions And Are Not

Implanted Devices

A pacemaker or implantable cardioverter defibrillator shows as a hard rectangular lump with a surgical scar, usually below the left collarbone. It does not rule out defibrillation. It only moves the pad. Place the pad at least an inch clear of the device so the current is not shunted through the generator casing. Full detail is in our guide to AED use with a pacemaker or ICD.

Pregnancy

There is no modified procedure. Standard adult pads, standard placement, standard energy. The reasoning is direct: the most effective treatment available for the fetus is a successfully resuscitated mother. See using an AED on a pregnant woman.

Water And Metal

Rain does not stop a defibrillation. Standing water does, briefly, and only long enough to drag the patient clear of the puddle. Metal grating, bleachers, and deck plate are safe as long as the pads are not touching the metal and no one is in contact with the patient at the moment of discharge. The full reasoning, including why these two are treated differently, is in wet, rain, and metal surfaces.

Children And Infants

An AED is used on children. Pediatric pads or a pediatric key reduce the delivered energy and are preferred for patients under eight years old or under roughly 55 pounds, but the absence of pediatric pads is not a reason to withhold defibrillation. Adult pads on a child are better than no defibrillation. We cover placement, the infant front-to-back position, and which units carry a key in using an AED on infants and children.

The Two Situations Where The Answer Is Genuinely No

A patient who is breathing normally and has a pulse. This is not cardiac arrest and an AED has no role. The distinction that trips people up is agonal gasping, an irregular snoring or gulping noise in the first minutes of arrest that looks like breathing and is not. Treat gasping as arrest. This is covered in depth in can you use an AED on someone who is breathing.

On yourself. Sudden cardiac arrest drops cerebral perfusion immediately, and consciousness goes with it. There is no scenario in which a person applies an AED to their own chest. This is the strongest argument for the thing we repeat most often: an AED protects a building, not an individual. It only works if someone else is present, knows where it is, and will go get it.

What This Means For Your AED Program

Every scenario on this page is a training scenario, not a purchasing one. But two of them have equipment consequences worth acting on.

First, spare pads. Half the exceptions above end with the instruction to use the second set. A program with one set of pads per unit has no margin for a hairy chest, a failed seal, or a pad applied and then repositioned. Second, a razor and a towel in the response kit. Both appear in this article repeatedly and neither is standard in every kit sold.

The Red Cross states that the chance of survival falls by roughly ten percent for every minute defibrillation is delayed. Every item in this article is a way of buying back part of one of those minutes.

Sources And Further Reading

Primary guidance for this article comes from the 2025 American Heart Association Guidelines for CPR and ECC, Part 7: Adult Basic Life Support, published October 2025, and from American Red Cross AED guidance.

This article describes what published resuscitation guidance says. It is not a substitute for hands-on training or for your device manufacturer's instructions for use, which govern that specific unit. Every AED model states its own pad placement, pediatric provisions, and environmental limits in its manual. Read it before you need it.