Breathing gas sometimes coming out of my nose in CCR diving. Mask issue or OPV ?

[WOB0.01J]

Hello Divers

I had a great time diving my CCR to improve my trim and buoyancy last weekend. Both of those things are improving significantly. Got to be down there for almost 2 hours. However, during my dive I have noticed something that is quite uncomfortable which was not a issue during my OC career ---- sometimes my nose would almost automatically exhale and breathing gas would keep coming out of my nose. I think this is might be because my OPV was not opened enough so that the loop volume is too high which leads to leaking out of my nose and not the OPV. Or because my mask simply doesn't fit me as well as I thought it did during my OC career.

Does anyone have any inputs? THX

 

[Alekseolsen]

As someone with as much as 1 CCR dive (and an upcoming class!) I'm a bit surprised to read of the OPV. I spent most of my dive making sure I had "minimum loop volume", thus there wouldn't be any triggering of an OPV - so is there differences to you unit or? Genuinely curious

 

[Superlyte27]

Hello Divers

I had a great time diving my CCR to improve my trim and buoyancy last weekend. Both of those things are improving significantly. Got to be down there for almost 2 hours. However, during my dive I have noticed something that is quite uncomfortable which was not a issue during my OC career ---- sometimes my nose would almost automatically exhale and breathing gas would keep coming out of my nose. I think this is might be because my OPV was not opened enough so that the loop volume is too high which leads to leaking out of my nose and not the OPV. Or because my mask simply doesn't fit me as well as I thought it did during my OC career.

Does anyone have any inputs? THX

What kind of rebreather? Probably diver error. Too much loop volume or solenoid firing to keep a ppo2 impossible to keep. Likely not a mask issue. You should be able to make the dive without a mask and not vent out your nose. Guessing you need to work on loop volume, make sure you’re not injecting o2 when you shouldn’t be and your OPV shouldn’t be venting any gas at all if everything else mentioned above is right.

 

[WOB0.01J]

As someone with as much as 1 CCR dive (and an upcoming class!) I'm a bit surprised to read of the OPV. I spent most of my dive making sure I had "minimum loop volume", thus there wouldn't be any triggering of an OPV - so is there differences to you unit or? Genuinely curious

OPV is over pressure valve. ADV is automatic diluent valve which can be triggered once the loop volume is less than what you need. OPV is when the loop volume gets too high and the system vents out some gas out of the loop. My unit has both OPV and ADV. Sometimes if i take a deeper breath than usual, the ADV will be triggered and increase the loop volume which could lead to OPV vent some gas out

 

[WOB0.01J]

What kind of rebreather? Probably diver error. Too much loop volume or solenoid firing to keep a ppo2 impossible to keep. Likely not a mask issue. You should be able to make the dive without a mask and not vent out your nose. Guessing you need to work on loop volume, make sure you’re not injecting o2 when you shouldn’t be and your OPV shouldn’t be venting any gas at all if everything else mentioned above is right.

I think it is because of loop volume issue. Sometimes I will take a deeper breath than usual which leads to ADV firing, increase the loop volume and my OPV was not open enough which leads to gas coming out of my nose

 

[rddvet]

This is likely diver related not unit related. I will say that the biggest hurdle ive had in ccr diving is chronic allergies and dealing with the loop. SInce its a closed circuit it affects your nose just as much as your lungs. That's what you're dealing with. My issues is with all of my congestion I can sometimes get alot of sinus pressure buildup from the loop unlike I've ever experienced in OC

 

[Dsix36]

I have hundreds of hours on several different rebreathers, including homemade, and still have to work at not venting out my nose during some dives. It is not a unit related issue at all, just a natural way of breathing that we have to relearn during rebreather dives.

 

[broncobowsher]

Sometimes it can also be a factor of the rebreather (where are the counterlungs) and body position. The rEvo rolled on it's back, head up slightly) really wants to make puffy cheeks.

 

[scubayinzer412]

it happend to me also sometimes. dont know why. but make happend lso in OC diving but with cc diving you noticed it.
whe it happend i pinch a little bit my nose.

 

[billgraham]

It's your brain. Also, you get better at managing loop volume as you go up and down and improve with time.