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The Frenzel mouthfill equalization technique

As it is teached at advanced F.BIZ courses
by: (c)Sebastian Naslund

How to equalize below RV-breakpoint (approx 30 meters).

Frenzel mouthfill is not a new equalization method, the mouthfill is a supportive technique that makes you able to equalize with Frenzel equalization below you RV-break point. The point where your lungs have been compressed to their minimum volume (residual volume), from which valsalva equalization is impossible. It basically means that you fill your mouth with air from the lungs before this point and then use this air to equalize with. The epiglottis must remain closed all the time. This technique was first put on paper by Eric Fattah.

The mouthfill can be done with a push from the torso/lungs, or better sucked up with a negative pack. They can be combined and that lets you draw the mouthfill somewhat later, but that is always risky. The best technique is to constantly top up until you feel you may not be able to do it fully again.

The bigger the mouthfill the better. It is a question of repetitive training to be able to hold a full mouthfill with out losing it. Below are 15 (dry) training techniques that enables you to train and master frenzel mouthfill.

Make sure valsalva works for you, feeling a good internal "click" when equalizing.

1) Breathe out with a half closed epiglottis, making a wheezing sound far down in your throat. Like fogging a mirror. Make sure you control the epiglottis. Switch to breathing in. Switch to breathing in staccato (opening/closing the epiglottis fast).

2) Close mouth and nose - fill mouth with air from lungs and then push it down again. Do it fast. It should be the mouth that moves the air, torso and stomach is totally relaxed.

3) Close epiglottis, close one nostril, do "air pumping" (in/out) through nose - pumping by opening and closing mouth cavity while keeping lips sealed. Try on empty lung, exhaling fully, closing epiglottis and feeling a vacuum in the chest. Torso/stomach not involved.

4) Now while doing above - close the second nostril - what happens? Do it again. You should feel pressure on the eardrums - this is frenzel equalization. Epiglottis must be closed. Push a bit harder with "mouth". If you fail to equalize you may be doing a "soft palate block" (see below).

5) Do full frenzel by squeezing the air in your mouth (diminish mouth cavity, pressing jaw and tongue upwards) causing pressure of air up towards sinuses. Imagine crushing a golf ball in your mouth. If you can not - then look at #7-9

Play with it, you will stumble upon the solution.


6) Frenzel has similarities to packing, Frenzel = push air up, packing = push air down with the mouth. Practice packing by taking a full breath (epiglottis closed) and then put the fingers normally used to hold a cigarette in front of your tensioned closed lips. Pinch your nose with the other hand. Now suck hard in through the imagined cigarette and fill your mouth, then seal your mouth, tense your cheeks and "swallow" the air into the lungs. Put your tongue tip up behind the upper teeth and squash the air, making your mouth cavity empty. Now suck through tight lips again. Over and over. If you fail, read the instructions again. If you succeed, be careful, Packing can be dangerous. Do not over pack - it can lead to air emboli (air bubbles moving into the bloodstream).

If you can pack through your nose you have full control over soft palate and epiglottis.

7) Frenzel demands that you tension nothing else but what is needed to get pressure in your mouth. Tension in other parts in your head and throat may cause you to fail due to soft palate block. The air has to have free passage upwards.

Do a relaxation exercise: Open your mouth, relax face (lips) and shake it (in fast repeating no-movement). Do it on exhale and make a relaxing sighing sound from stomach.

8) Do #5 again. And try it with different head positions. Chin down, head to side, move jaw.

9) If you still can not equalize, you are doing a "soft palate block". In order to understand what that is, you must now voluntarily do a palate block, blocking the passage of air upwards.

- Find your soft palate by breathing in and out through (only) your nose while having your mouth open. Switch between exhaling through mouth and then nose. It is your soft palate that blocks and opens.

To prove that you actually are blocking, you must be able to produce a "geeky sound". Do frenzel (air in mouth, epiglottis closed, compress air, push it upwards AND soft palate block). If you keep your nostrils unblocked you will be able to produce a sound through your nose. Let a little air pass the soft palate block while using frenzel to push air upwards.

Understand that if you can not find and tension a muscle, neither can you find and relax it.


Once you master Frenzel and frenzel mouthfill (which can take a long time), you will find a deeper limit for your equalization. Maybe so deep that hypoxi becomes your next problem (you can equalize deeper than oxygen will last), be careful.

Once you are able to do longer divetimes, you will be able to do deeper dives, so deep that the mouthfill will be used up. How to solve it?

1) The obvious solution is a bigger mouthfill.

A mouthfill and cheekfill. Beginners often fail to take a FULL mouthfill. It should involve a wide jaw opening, full blown cheeks, and filled lips. To push the last bit of air out of your lungs, suck up your diaphragm to help fill your mouth. Train this diaphragmatic movement after breathing out as much air as you can. Do it with a reverse packing movement with the mouth. Epiglottis has to close immediately after.

This movement may involve arching your back.

2) Another way to improve the mouthfill equalization is to take it on the absolute limit of your VC capacity. The deeper you can take it, the deeper it will last.

3) From here on it is about nurturing and making the most of that ONE mouthfill. Being able to use it to the last drop. When the mouth is empty jaw movements and lip movements (gliding lips side to side over the front teeth). Being able to do BTV (handsfree opening of the eustachians) will help at this moment.

Different volumes of mouth and ways of sealing the mouthfill:
1) Full mouthfill:
...mouth cavity, upper throat (above epiglottis), jaw opened fully (lips sealed), cheeks pumped, and air in front of teeth (lips "filled"). Usually the start of a very good mouthfill.
2) Same as above, but without pumped cheeks and lips. A smaller volume, but more controllable and usually stronger. This is where you will end up when going deeper.
3a) Front mouthfill:
...soft palate sealer (root of tongue goes up), the air is trappep in the front of the mouth and will not be lost if you swallow.
3b) Back mouthfill:
...tongue touches roof of the mouth just behind the upper front teeth. Mouthfill is getting smaller and smaller.
4) Empty mouth - mouthfill. Yes when the mouth is empty there is still air left that can be used to equalize by squeezing the air in the sinues and upper throat by compressing the upper throat area by pulling back jaw, pulling chin to chest, drawing back tongue (without blocking passage up to esutachians).

(Full cheeks but with jaw closed, teeth "closed". Not a very usefull method.)


If you, at the surface, can empty your lungs down to Residual Volume and along a rope sink feet first using a mouthfill to equalize without any pain in your ears to lets say 5 meters (15 feet) then you are using frenzel mouthfill. This evaluation and training method will put you at risk of lung squeeze and early hypoxi (blackout). It is extremely advanced and should be done under supervision.

Being able to use a mouthfill from the surface down to 10 meters proves that you could theoreticly use a full mouthfill from 30 meters down to 70 meters.


Taking a mouthfill is one thing, holding on to it another. It is very common to loose it. If you do, there is no need to go complaining about it, like it is something that HAPPENS TO you. You dropped it because you have not trained enough.

Now some exercises that will train you not to loose your mouthfill during the dive. You usually loose it because you swallow. You swallow because you have gathered saliva in your mouth, or you have an urge to breath, or you have contractions. Here comes a few simulations on land.

Do not loose your mouthfill

1) Take a full mouthfill, hold your breath, wait for saliva to assemble in your mouth - do not swallow, do not loose your mouthfill. Concentrate on that sealed epiglottis. Focus.

2) Full mouthfill, hold your breath, wait for contractions, do not loose your mouthfill. This you can rehearse in every static breath hold training you do.

3) Same as above, but now equalize with Frenzel in between contractions. Do it with mask or noseclip. Now, on land. No need to go to the sea or pool.

4) Now do the above but include mask (or noseclip) and walking apnea.

5) Learn to do a swallow movement without losing the mouthfill down into the lungs. Swallow, after sealing the passage down to the throat by pushing up the back of your tongue (you will unfortunatly loose some air with this manouvre, but salvageing most of the mouthfill). Better not to swollow.

If all this was easy and you do not know what the fuss is about, you may not be doing a frenzel mouthfill, but be one of those gifted persons that can do BTV, handsfree equalization.

On the other hand if you are confused and frustrated, you are quite normal: start from the beginning again. It is an advanced technique that takes training to learn. There is a longer text on the topic to be found at

tongue tip just below lower teeth

Mouth mouthfill open jaw fully
Ways of sealing the mouthfill: