To place an AED, you put one pad on the upper right chest, just below the collarbone, and the second pad on the lower left side of the chest, a few inches below the left armpit. The AED itself will walk you through each step with voice prompts, but knowing the basics ahead of time can save critical seconds when they matter most.
Standard Pad Placement on Adults
Every AED comes with a diagram printed on the pads or the device showing exactly where each pad goes. The standard position, sometimes called anterolateral, puts one pad on the right side of the bare chest between the collarbone and the nipple. The second pad goes on the left side of the torso, a few inches below the armpit, roughly along the lower ribcage. This positioning sandwiches the heart between the two pads so the electrical shock can travel through it effectively.
Press each pad firmly against the skin so there are no air pockets or wrinkled edges. A pad that doesn’t stick well can reduce the shock’s effectiveness or cause the AED to display an error. Once both pads are on, stop touching the person and let the AED analyze the heart rhythm. It will tell you whether a shock is needed and when to press the button.
Preparing the Chest First
The pads need direct contact with bare, reasonably dry skin. That means removing or cutting away clothing over the chest before placing anything. A few common situations require a quick extra step:
- Wet skin: You don’t need to dry the whole body. Just wipe the two areas where the pads will go with a towel, shirt, or whatever is handy. If the person is lying in standing water, move them out first if you can do it in under 10 seconds. A wet surface like a rain-soaked sidewalk or damp grass is safe to use the AED on, as long as the pads stick to dry skin and there’s no water pooled between them.
- Thick chest hair: If the pads won’t stick because of dense hair, shave the pad areas quickly. Most AED kits include a razor for this reason. If shaving is taking too long, press the pads down as firmly as you can and follow the AED’s prompts rather than delaying.
- Medication patches: If you see a transdermal patch (nicotine, pain medication, hormone therapy) where a pad needs to go, peel it off, wipe the area clean, and then place the pad. Use gloves if they’re available, since some patches can absorb through your skin too.
Working Around Pacemakers and Implanted Devices
Some people have a pacemaker or implanted defibrillator under the skin of their upper chest. You can usually see or feel a small, hard lump about the size of a matchbox, most often just below the left collarbone. If you spot one where a pad would normally go, place that pad at least four finger-widths away from the device. This keeps the AED’s shock from being absorbed or deflected by the implant. Don’t let the presence of an implanted device stop you from using the AED. The person is in cardiac arrest, and the AED is still their best chance.
Pad Placement for Children and Infants
Many AED kits include a separate set of smaller pediatric pads or a switch that reduces the energy level for children. If you have pediatric pads, use them for children under about 8 years old or under 55 pounds. If pediatric pads aren’t available, use adult pads rather than doing nothing.
For smaller children and infants, the two pads may be large enough to touch each other on the chest. If that’s the case, use front-and-back placement instead: one pad on the center of the chest and the other on the center of the back, directly behind the first. This still allows the electrical current to pass through the heart. The AED’s voice prompts will guide you either way.
Bras, Jewelry, and Metal Surfaces
A common concern is whether underwire bras or metal jewelry will cause problems. The International Liaison Committee on Resuscitation reviewed this question and found that in animal testing, shocks delivered directly through underwire caused no arcing, no burns, and no harm to the rescuer or the device. That said, the pads still need to sit flat on bare skin in the correct position. In most cases, you’ll need to at least push the bra out of the way or cut it. If you can reposition it enough to get full skin contact in both pad locations, that’s sufficient. Necklaces that sit above the pad areas don’t need to be removed, but if a piece of metal jewelry sits directly under where a pad goes, move it.
Metal surfaces like grates, bleachers, or steel decking are safe. Metal and snow are both poor enough conductors that the shock stays between the two pads on the person’s chest, not through the surface beneath them.
Does Pad Position Affect Survival?
The standard upper-right and lower-left position is what AED diagrams show and what most people learn in CPR training. But the 2025 American Heart Association guidelines reviewed the evidence and found that alternative positions, including front-and-back placement, work just as well. One study of over 1,000 shocks found identical success rates between standard and front-to-back positioning (about 82% for both). For a bystander using an AED, the message is straightforward: the standard position works, and if something prevents you from using it (a pacemaker on one side, a wound, a large patch you can’t remove), placing one pad on the front of the chest and one on the back is equally effective.
The Steps in Sequence
Pulling it all together, here’s the full sequence from the moment you have the AED in hand:
- Turn the AED on. Open the lid or press the power button. Voice prompts begin immediately.
- Expose the chest. Remove or cut clothing. Dry the skin if wet, shave if needed, remove medication patches.
- Peel and place the pads. Upper right chest, lower left ribcage. Press firmly with no air gaps. For small children, use front and back if the pads would overlap.
- Clear the person. Make sure nobody is touching them. The AED will analyze the heart rhythm.
- Follow the prompts. If the AED says to shock, confirm no one is touching the person and press the shock button. If it says no shock is advised, continue CPR.
- Resume CPR immediately after the shock. The AED will re-analyze every two minutes and tell you if another shock is needed.
Speed matters more than perfection. A pad placed slightly off from the ideal spot still delivers a shock through the heart. Hesitating to get everything exactly right costs time that the person’s brain can’t afford to lose. Get the pads on bare skin, get them roughly in the right spots, and let the machine do its job.