Nitrox Under The Boat?

[HJeffreyM]

Might not be if it reduces your safety stop before the next dive.

Don't you mean surface interval?

 

[Jediscuba]

Just a thought, not a proven fact but....
At 15' down an ocean swell of 5' is only 30%
at 5' down a swell of doubling your depth.

Your instructors idea might be valid in perfectly flat seas but you might eno****er a lung over pressurization while making "shallow" exteded stays.

 

[ianr33]

Don't you mean surface interval?

Err........Yes !

 

[Jeff Toorish]

Dr. Deco explained it perfectly, as usual. One other thing to remember, keep breathing off that regulator while climbing back onto the boat, especially if the boat's engine is running. The exhaust fumes from the boat will stop your offgassing.

Jeff

 

[paddler3d]

Hello HJeffreyM:

Breathing the tank down before climbing onto the boat is a good idea. Some call it the “hidden stop.” It reduces nitrogen loads before you exert muscle strain and reduces the chance for decompression bubble formation/growth.

Dr Deco :doctor:

Will you average dive computer continue to calculate nitrogen loading will doing this, so that in theory you can exit the water with no load, just as if you had a surface interval?

 

[HJeffreyM]

I don't know about other DCs, but my Elite T3 (hoseless, AI) returns to NORM SURF mode at 4fsw. I assume it begins calculating my offgassing with air at the surface at that time.

However, I continue to breathe off the tank at the surface for as long as possible (500psi, or I absolutely must change tanks for the next dive) for two reasons: 1) whatever my computer says, I know I'm better offgassing on 32 than 21 PO2, and 2) I paid for it!!! Yup, I paid extra for every tank of Nitrox so I'm going to obtain all the advantages I can from each one.

Anyway, Dr. Deco made it pretty clear that there's great benefit with Nitrox in doing both a very slow ascent from 15fsw and continuing to breathe it at the surface. I will keep doing that whenever possible.

Happy diving!

 

[DandyDon]

One other thing to remember, keep breathing off that regulator while climbing back onto the boat, especially if the boat's engine is running. The exhaust fumes from the boat will stop your offgassing.

Jeff

Hey, never thot of that. I often keep the reg in my mouth until well onto the boat for safety reasons usually, in case of a fall - at least on big boats. On smaller ones I am more likely to take my rig off in the water for the hand to pull up.

However, I continue to breathe off the tank at the surface for as long as possible (500psi, or I absolutely must change tanks for the next dive) f

Breath it down lower above 15 ft or onboard if you want. It'll take forever tho.