A chest seal is an adhesive dressing placed directly over a penetrating wound to the chest to prevent air from entering the chest cavity. Correct application takes under a minute, but the steps before and after matter just as much as the seal itself. Here’s how to do it right.
When You Need a Chest Seal
Any open wound to the chest that penetrates into the chest cavity needs to be sealed. These are sometimes called “sucking chest wounds” because air gets pulled through the hole with each breath, collapsing the lung on that side. The classic sign is an audible sucking or hissing sound at the wound site. You may also see bubbling in or around the wound, which the American Association for the Surgery of Trauma considers a definitive indicator. In some cases, you can actually see the lung through the wound opening.
The chest wall extends from the collarbones down to the bottom of the rib cage, and includes the sides of the torso under the armpits. Any penetrating wound in this zone, whether from a gunshot, stabbing, or shrapnel, is a candidate for a chest seal.
Check for an Exit Wound First
Before you apply anything, check the person’s entire torso for a second wound. Bullets and other projectiles often create both an entry and an exit wound, and both need to be sealed. Roll the person enough to visually inspect their back, and check under the armpits and along the sides of the torso. These areas are easy to miss, especially when clothing is in the way. Cut or remove clothing to expose the full chest.
If you find two wounds and only have one chest seal, use the seal on the larger wound and improvise on the smaller one (more on that below).
Vented vs. Non-Vented Seals
Commercial chest seals come in two types: vented and non-vented. Both work by creating an airtight barrier over the wound, and both immediately improve breathing and blood oxygen levels after application.
The critical difference shows up if air continues to leak inside the chest cavity after the seal is on. In animal studies, non-vented seals trapped that accumulating air with nowhere to go, leading to a dangerous buildup of pressure called tension pneumothorax in every subject after roughly 1.4 liters of trapped air. Vented seals, which have small one-way valves that let air escape outward but not enter, prevented this entirely, even with up to 2 liters of additional air injected.
A vented seal is the better option when available. If you only have a non-vented seal, use it. Sealing the wound quickly is more important than having the ideal equipment, but you’ll need to monitor the person closely afterward.
Step-by-Step Application
Prepare the Skin
The seal needs to stick firmly to the skin surrounding the wound. Blood, sweat, and body hair all compromise adhesion. Wipe the area around the wound as dry as you can using gauze, a cloth, or whatever clean material you have. Some commercial chest seal kits include gauze for this purpose. You don’t need to clean deep into the wound itself. Focus on getting the skin within a few inches of the wound edges dry enough for the adhesive to grip.
Time It With an Exhale
If the person is conscious and able to follow instructions, ask them to breathe out fully and hold it. Applying the seal at the end of an exhale pushes the most air out of the chest cavity before you close the wound. If the person is unconscious or unable to cooperate, apply the seal as quickly as possible without waiting.
Peel and Place
Remove the backing from the chest seal. Center it directly over the wound, making sure the adhesive border extends at least an inch beyond the wound edges in every direction. Press it down firmly, starting from one edge and smoothing outward to avoid trapping air bubbles under the adhesive. Run your fingers along all the edges to ensure a complete seal against the skin.
If the seal has a valve (vented type), make sure the valve sits directly over or very near the wound opening so trapped air can escape through it.
If You Don’t Have a Commercial Seal
When no chest seal is available, you can improvise with any non-porous material: plastic wrap, a section of a plastic bag, or even the packaging from a piece of medical equipment. Cut it large enough to extend well beyond the wound edges and tape it down on three sides, leaving the fourth side open. This creates a crude flutter valve: air can escape from the untaped edge during exhale but the plastic gets sucked against the wound during inhale, partially blocking air entry. This method is far less reliable than a commercial seal, and the Royal College of Surgeons of Edinburgh notes that three-sided dressings are often ineffective. Use one only as a last resort.
What to Watch for After Application
Once the seal is on, your job shifts to monitoring. The biggest threat is tension pneumothorax, where air pressure builds inside the sealed chest cavity and starts compressing the heart and the uninjured lung. This can develop within minutes and is life-threatening.
Watch for these warning signs:
- Worsening breathing difficulty despite the seal being in place
- Visibly distended neck veins, caused by pressure backing up blood flow to the heart
- Dropping blood pressure or increasing heart rate, which you may notice as the person becoming pale, confused, or losing consciousness
- The windpipe shifting to one side, visible or felt at the base of the throat, though this is a late sign
- Bluish skin color, particularly around the lips and fingertips
How to “Burp” a Chest Seal
If the person’s breathing gets worse after application and you suspect pressure is building, you need to release it. With a non-vented seal, this means “burping” the seal: peel up one corner or edge to break the airtight barrier, let the trapped air rush out (you may hear a hiss), then press the seal back down. This can be repeated as many times as needed.
Tactical Combat Casualty Care guidelines put it simply: lift one edge, let the tension decompress, then reapply. If burping doesn’t relieve the symptoms, remove the seal entirely for a few seconds to allow full decompression before resealing. A vented seal handles this automatically through its valve, which is one reason it’s the preferred option.
Positioning After the Seal Is On
If the person is conscious and breathing, sitting them up or positioning them leaning slightly forward on the injured side helps. Gravity assists drainage and keeps the uninjured lung in the best position to work. If they’re unconscious but breathing, placing them on the injured side (recovery position with the wound down) serves the same purpose, letting the good lung expand freely while gravity helps keep blood and fluid from flooding it.
Keep the person as calm and still as possible. Every extra breath and every movement increases oxygen demand at a time when their lung capacity is reduced. Get them to definitive medical care as fast as conditions allow.