Avoiding and Treating Reverse Block During Scuba Diving Ascent

A reverse block may occur upon ascending to the surface, as air expands in our tissues. It’s pretty rare to experience a reverse block. Most divers would not experience reverse block while scuba diving as long as taking the right measures to prevent it from happening.

Depth, pressure and volume. Some background:

The deeper we get the more pressure is applied on our body. These changes are more drastic at shallow water, where even a small change in depths can be easily felt. Every 10m/33ft of salt water adds 1bar/atm of pressure to the ambient pressure applied on us. Adding 1atm/bar of pressure due to the air pressure and you’ll experience 2 bars at 10m/33ft, 3bars at 20m/66ft and so on.

DEPTH 0m/0ft 10m/33ft 20m/66ft 30m/100ft
PRESSURE 1atm/bar 2atm/bar(1+1) 3atm/bar 4atm/bar
VOLUME 1 liter 1/2 liter 1/3 liter 1/4 liter

As we ascend air bubbles that were dissolved in our tissues will expand. Under normal circumstances air will simply escape our tissues to our bloodstream and out it goes when exhaling.

A reverse block is caused by mucus blocked sinuses that prevent these air bubbles from escaping our body. Upon ascending, trapped bubbles press on the sinuses which cause serious pain above the eyes, around the chicks, and all the way down to the teeth.

How to avoid a reverse block?

Luckily, reverse block can be easily avoided for most divers:

  1. Those with chronic sinus problems should not dive, unless checked by a dive physician.
  2. Never Dive with a cold. Diving with a cold increases your chances of experiencing a reverse block, which is something I don’t recommend trying to temper with. When having a cold you may have your sinuses blocked which can make it difficult to equalize upon descent and even more serious, experiencing a reverse block upon ascent.
  3. You may use decongestion drugs, as long as you make sure these will not ware out during the dive, or else you’ll find yourself stuck at mid-water struggling with a reverse block.

What do I do if I experience a reverse block?

  1. Relax. All you have to do is to stop your ascent and signal to your body you have some problems and you need to take your time ascending to the surface.
  2. Descend a few feet/meters, that increases water pressure and shrinks those trapped air bubbles, which decreases the pressure on your tissues and may relieve the pain.
  3. Take your time. Equalizing reverse block may take some time, so make sure you and your buddy have enough air left in the tank. Some reverse block cases are only solved after 10-15 minutes so be patient and don’t force your ascent.

Treating Reverse Block

If you do ascent to the surface while experiencing a reverse block your condition mat only get worse. It may also lead to sinuses rapture, which on a minor scale may lead to some nose bleeding, but may also lead to sinuses infection if left untreated.

look for some professional help if experiencing serious reverse block.




  1. I suffer from reverse block after I Ascend, each dive. It causes me no pain and I don’t realise I have it until ont he surface,until my buddy makesme aware I have a little nose bleed.

    I find when I am Ascending I get quite a bit of flem on my chest riseing up into my throat , I have never dived with a cold nore would I.

    Can anyone think of a cause for this or give me and Advice please. This has not stopedme from diving as I have just completed my Advanced course.

  2. Hi Jodie,
    a minor nose bleed can happen from time to time, and I’m not that concerned about it , but I’m more worried about your chest, and I’d definitely encourage you to see a physician before you continue diving. As I’m not a dive physician . Not me, nor any dive professional should take responsibility for your health giving you these kinds of advices.

  3. I had a reverse block back in july and it gave me a really bad head ache and it’s been off and on but for almost a month it hasn’t changed and I still have a head ache in february and I don’t know why does anybody?

  4. Hi Nick.
    I’m not a physician and have no means to consult you on matters I shouldn’t. My guesses are you may have sinuses infection, but you wouldn’t know for sure till you go check it out.
    Feel Well,

  5. Nick – I’m interested to know if you got anywhere with your issue…I suffer similar effects – I really struggle with equalisation esp reverse blocks (I burst an ear dum on my last dive!) I suffer with sinus issues a few times a year and I have a feeling this is a factor.

  6. Hi Steve,
    I also suffered from sinuses issues recently, and I encourage you to get checked. You probably will be advised to stay off diving till you recover. Diving with sinuses issues is not recommended, trust me. Additionally, I will deferentially suggest you to get your ears checked too, I cannot stress enough how serious neglecting and ignoring these symptoms might be.

  7. I also suffer with the reverse blockage issue. I can no longer free dive as I can’t come up as fast as I would like. I find the best way to clear the ears when ascending in a scuba dive is to till your head over with your ear facing towards the surface. I can actually feel and see the air bubbles come out of my ear. This has been the only thing that I’ve found to help. I’d love to hear of any other treatments or tricks to resolving this issue.

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