Lung Packing in Freediving: How It Works and the Risks

Lung packing is the practice of forcing extra air into your lungs after they are already full. You take the deepest inhale you can, then keep adding air in small gulps using your mouth and throat as a pump. The technical name is glossopharyngeal insufflation, usually shortened to GI. Each gulp adds a little volume above your normal total lung capacity, so a heavy packer can hold noticeably more air than a single maximum breath would allow.

This sits at the advanced and frankly controversial end of the sport. It is not a beginner technique and it is not a shortcut. If you are still building your base, your time is far better spent on breath-hold training and relaxation than on squeezing extra liters into your chest. Packing only starts to matter once everything else is already dialed in.

Lung packing

Glossopharyngeal insufflation (GI). Pushing extra air in above a full inhale. Adds volume above total lung capacity.

Reverse packing

Glossopharyngeal exsufflation. Pulling small amounts of air up from the lungs at depth to refill a mouthfill for equalization.

Total lung capacity

The maximum air your lungs hold on a normal full inhale. Packing aims to exceed this; reverse packing operates well below it at depth.

Your diaphragm and rib cage can only inflate your lungs so far. Once they are at their limit, you physically cannot inhale any more through normal effort. Packing bypasses that ceiling by using the muscles of the mouth, tongue, cheeks, and throat as a separate pump that operates after the inhale is finished.

The sequence

1. 01 —Take a full, slow, maximum inhale until your chest and belly are completely expanded. This is your starting point, not the end.
2. 02 —Close the glottis (the same valve you close to hold your breath) to seal the air already in your lungs and stop it escaping back up.
3. 03 —Take a mouthful of air by dropping the jaw and tongue, the way you would scoop water with your mouth.
4. 04 —Seal the lips, raise the tongue and compress the cheeks, and push that mouthful downward against the closed glottis.
5. 05 —Open the glottis for an instant so the pressurized mouthful is forced down into the lungs, then close it again to trap the new volume.
6. 06 —Repeat in small, controlled gulps. Each pack adds a fraction of a liter. Stop at the first sign of tightness, dizziness, or visual disturbance.

Done correctly the motion is smooth and almost gentle. The common beginner error is treating it like force: big, hard gulps driven by aggression. That is exactly the version that injures people. The pump should feel deliberate and quiet, not strained.

There are three honest reasons divers pack, and one of them is not what most beginners assume.

More oxygen on board

The obvious one. More air means more oxygen stored, which can extend a hold. But the gain is modest. The extra volume is a fraction of total lung capacity, and the oxygen it adds is small relative to what relaxation and efficient diving save. A diver who packs but cannot stay calm gains far less than one who never packs but is genuinely relaxed.

More air for equalization at depth

This is the reason packing matters most for depth divers. As you descend, lung volume shrinks under pressure and you run out of air to push into your ears. Starting with more total volume means more air available for your equalization technique deep in the dive, where running dry is what ends most deep attempts.

Lung and rib cage flexibility

Gentle, progressive packing under supervision is sometimes used to maintain chest and lung wall flexibility, which deep divers need as the rib cage compresses at depth. This is a separate goal from maximizing a single hold, and it is the use case where small numbers and patience matter most. Stretching the chest is not the same as cramming it full before a dive.

This is the part beginners skip and the part that matters most. Packing pushes pressure inside your chest above what any normal breath produces. Your lungs and the circulation inside your chest are not designed for that, and the consequences are documented in the medical literature, not theoretical.

Lung barotrauma and pneumothorax

Overfilling the lungs raises transpulmonary pressure, the pressure difference across the lung wall. Push it too high and lung tissue can tear. Documented outcomes include pneumothorax (a collapsed lung), pneumomediastinum (air leaking into the chest cavity around the heart and airway), and lung bleeding. Studies on trained breath-hold divers have found lung injury from glossopharyngeal insufflation, and asymptomatic air leaks appear common enough that researchers consider mild barotrauma a real hazard of the technique.

Arterial gas embolism

If air is forced through torn lung tissue into the bloodstream, it can travel as a gas embolism. Reaching the brain, that can cause stroke-like neurological symptoms. This is rare, but it is the worst-case chain that starts with overpressure in the chest.

Packing blackout

The high pressure inside your chest squeezes the large veins returning blood to your heart. Less blood returns, so the heart pumps less out, and blood pressure can drop sharply. The result is a packing blackout: divers go dizzy, see stars, and can lose consciousness while still standing on the deck or floating on the surface. This is why you never pack standing up, and why fainting after packing has nothing to do with running out of oxygen.

None of this means packing is guaranteed to hurt you. It means the margin for error is small and the failure modes are severe. That combination is exactly why it belongs at the advanced end of the sport, learned slowly and never improvised.

Reverse packing, technically glossopharyngeal exsufflation, runs the pump backward. Instead of pushing air into full lungs on the surface, you use the throat at depth to pull a small amount of air up out of the compressed lungs and into your mouth, refilling the mouthfill you use to equalize. It is the deep-diving counterpart to lung packing, and the safety picture is different.

Where lung packing is widely viewed as risky, small and gentle reverse packing is a mainstream part of advanced equalization and is taught on serious depth courses. The key word is small. The technique works best as a tiny, efficient pull that brings up just enough air for the next equalization while you stay relaxed. Learn it alongside breathing technique and equalization, not in isolation.

Like forward packing, reverse packing should be learned dry first to find the motion, then taken into the water gradually. Practicing it standing carries the same fainting risk as forward packing, so do your dry work sitting or lying down.

The single most important rule: do not learn packing from an article, this one included. Glossopharyngeal techniques are instructor-led skills. A certified course that specifically covers advanced equalization and lung volume work is the only responsible way in, and a good instructor will tell you when you are not ready yet. If you are weighing courses, our guide to choosing a freediving certification covers what to look for.

The progression that keeps you intact

1. 01 —Master the fundamentals first. Relaxation, CO2 tolerance, and clean equalization should already be solid. Packing on a weak base is risk with no payoff.
2. 02 —Start dry, sitting or lying down. Never pack standing. The packing blackout drops people where they stand, and a fall is its own injury.
3. 03 —Use one or two gentle packs to begin. Learn the motion at low volume before you ever consider adding more. Smooth and quiet, not forced.
4. 04 —Have a person present. Dry packing alone risks fainting unobserved; in-water work always requires a trained buddy watching continuously.
5. 05 —Respect every stop signal. Chest tightness, dizziness, visual changes, coughing, or pain means stop for the day. There is no rep worth a torn lung.
6. 06 —Add volume over months, not sessions. Lung and chest flexibility adapts slowly. Rushing the numbers is the single clearest path to injury.

Lung packing earns a place in some advanced divers' toolkits, mostly for equalization volume and chest flexibility rather than the oxygen bump beginners imagine. It also injures people every year who treated it as a trick rather than a serious technique. If you build patiently, learn in person, and stay honest about the stop signals, it can be done carefully. The fastest way to get hurt is to skip the base and chase the gulps, so put your reps into the fundamentals first and let packing wait until your diving actually asks for it.