Slow Ascent / Bad Dive Shop Owner?

[MongoliaLuke]

Hi guys,


So today was diving a wreck, it was a super small WW2 fighter plane in around 40m of water. Anyway we spent 10mins on the wreck, and 2 mins before we enter deco we decide to ascend slowly back up. Apart from seeing the wreck on a sandy bottom this is pretty much a blue water dive.


Anyway, on the ascent, one of the tec guys who was buddy with someone else (not even my buddy) was telling me i should ascend faster than my current rate and shaking his head disapprovingly in water.


This really annoyed me because it was part of my buddy and i's plan to ascend slowly given the depth and the deep depths of the other dives we were doing that day. Also as we were ascending my computer (Suunto Zoop) was telling me i was ascending at a good pace, not too fast (in the yellow/red warning zone). This really angered me as i got the feeling the tec guy (Also the dive shop owner) was just trying to conserve air so that we could use the same air tank to go dive on another wreck after this one instead of having to go home to get new cylinders, which he wanted to do.


This annoyed me for several reasons because:
1) I would rather be safe than sorry, and this was pre-arranged plan so i dont think the Tec diver had any reason to get annoyed with us.
2) The tec wanted us to conserve air so we had enough air to go to the next wreck (Only 20m max), and his reason was that he didnt like the time it takes to offload the boat, refil and get going again etc. This is the same guy that also tried to get me to change my PO2 level on my watch to 1.5, rather than 1.4, and got annoyed at me when i changed it back to 1.4. Really sounds like he is being a cheapshake and trying to hurry up the dive like he had better things to do given his wanting us to use this one cylinder for two dives, and also all of the above i have mentioned.

In the end we did go back and get second cylinders, and i am glad we did, as this dive shop owner/tec guy got angry, so it was a good bit of in your face!


Let me know your opinions, is this pretty unprofessional for a dive shop owner? Or pretty reasonable and i am being selfish by not conserving my air more and should have ascended quicker?


Cheers,
Luke

 

[Doubler]

Plan your dive and then dive your plan. Unless he had input into your plan or you were doing something dangerous he should leave you alone. My 2 pence.

 

[MongoliaLuke]

But its not too dangerous to ascend slowly right? The slower the better i guess? Or do you run into problems if too slow that i haven't considered before? Like re-absorbing nitrogen etc... but i guess not as its all a basic physics and pressure game right?

 

[kelemvor]

Sounds like you've found a dive op to avoid.

 

[fred3798]

Name him and shame him. I's be surprised that PADI would take kindly to a PADI shop pushing for 1.5 PO2 or faster ascent.

 

[MongoliaLuke]

Ha i will name and shame when i finish diving with them! I have already pre-paid for my diving there, so dont want to name and shame and then they read this and become even more unprofessional to me!

Plus maybe it is a bit unfair for me to name and shame, i have read some really good reviews for them recently, and so maybe my experience was just a once off, and to be fair they were pretty busy to perhaps they were under a lot of stress!

 

[boulderjohn]

But its not too dangerous to ascend slowly right? The slower the better i guess? Or do you run into problems if too slow that i haven't considered before? Like re-absorbing nitrogen etc... but i guess not as its all a basic physics and pressure game right?

Yes, there is such a thing as too slow. While you are ascending, some of your tissues are still taking on nitrogen. Too slow, and the nitrogen you are taking on is counteracting the benefit of the nitrogen you are letting go.

A study published by DAN compared three ascents rates (10 FPM, 30 FPM, and 60 FPM) and determined that 30 FPM was the best of the three and 10 FPM was the worst. It also concluded that safety stops were more important then the ascent rate.

 

[Sevenrider860]

But its not too dangerous to ascend slowly right? The slower the better i guess? Or do you run into problems if too slow that i haven't considered before? Like re-absorbing nitrogen etc... but i guess not as its all a basic physics and pressure game right?

In a tech dive with deco obligations, a slower ascent to the stop than planned ( usually 10m/min ) is not safer. The deco plan is based on a set ascent rate. If you make a slower ascent, then your plan is no longer valid. So there are instances where slower ascents are not safer.

 

[OkByMe]

60 to 60 or mid point, 30 from 60 to 20, slow to zip, hang at 15 for 5 or 6, creep to the surface. That is a good plan. Faster ascent from deeper water prevents additional N load - rate of pressure change is less so take advantage. I think that was what he was trying to say, but should have been discussed as part of the pre-dive briefing. Do it or not, your choice.

As for PPO, I started with 1.4 and progressed to 1.6 after realizing no issues. I have often thought of trying a little higher under controlled conditions, But I guess there is not point in putting my head in the noose, just to see if I'll Hang, even if there is someone there to cut the rope. Re-set to 1.4 on busy multiple dive days or loaded (work hard) dives or solo, just for safety.

 

[Scared Silly]

PPO2 - if 40m was your max depth then assuming air your PPO2 was 1.05. So I am not sure what they issue would be? Were you diving NITROX?? For me if diving NITROX at 40m I would be fine with a max 28% (1.4 PPO2) given it was to be a short no deco dive.

That said many tech divers believe that using a PPO2 of 1.2 gives a wider margin of safety during the working part of the dive. During the ascent 1.4 is fine with a switch to 1.6 at 6m for 100% O2


As for the ascent rate. The common rate is 10meters/min (30ft/min). However, many tech divers will use an ascent rate of 20meters/min (60ft/min) when coming up from deeper depths <40m but only until around 20-30m when a stop might be done for a gas switch. After that a 10meters/min would be used.

So in your case coming up from 40m to 20m at 20m/m instead of 10 m/m would have saved 1 min. and maybe 3 cuft of gas. Hardly enough to that it would make any difference for a second dive.


IMHO the op is basically making an issue with no gain while making the customer uncomfortable.