unlimited dives shallower than 30 ft. min S.I.

[Spoon]

guys i know you can basically stay shallower than 30ft without time limits and wanted your opinions or theories f you can do multiple repeated dives over a 12-13 hour period with minimum si? just asking because i did 8 dives last week. only dive 1 to 3 were deeper than 30. if you waited long enough to offgass the nitrogen from dive 1 to 3, then theoretically you can dive onwards with min S.I since you are diving shallower than 30 ft?

 

[clgsamson]

use a wheel bro...

 

[Spoon]

use a wheel bro...

i have bro first 3 dives are considered but theoretically dive 3 onwards is unlimited. the wheel doesnt account for physilogical factors like: stress, fatigue, dehydration etc. brought this up with the local dan rep and he said that its possible but fatigue can play a likely role in the later dives.

 

[LavaSurfer]

Just curious
Were you using EAN?
If so, What % and would CNS clock come into play after 8 dives (possibly 8 hours or more at those depths)?

 

[Spoon]

Just curious
Were you using EAN?
If so, What % and would CNS clock come into play after 8 dives (possibly 8 hours or more at those depths)?

nope i was just diving on air. all of the dives after dive 3 were in the 30-35 min range and made sure i wouldnt exceed this depth. also wouldnt being at this relatively shallow depth at prolonged dives be the same as offgassing nitrogen close to the surface?

saw a show in the discovery channel, "marine machines" they featured a guy who stayed underwater breathing air from a depth of 15 ft for 3 whole days..

 

[LavaSurfer]

nope i was just diving on air. all of the dives after dive 3 were in the 30-35 min range and made sure i wouldnt exceed this depth. also wouldnt being at this relatively shallow depth at prolonged dives be the same as offgassing nitrogen close to the surface?

saw a show in the discovery channel, "marine machines" they featured a guy who stayed underwater breathing air from a depth of 15 ft for 3 whole days..

Going by what I was tought, dive the tables and as many times as you want. Just watch the RN. In class we walked through a day diving 7 dives with varying SI's and still had time to spare.

 

[Jamdiver]

Interesting question Spoon.

Well strictly speaking they are time limits i.e (NDL limits) on dives to 9 meters (30 feet) however you'd need to be in the water for close to 4 hours on the first dive for this to be an issue.

I've attached 2 BSAC tables for analysis.
Should note that BSAC tables are more conservative than PADI.

Assuming that after dive 3 you've offgassed all nitrogen from the previous dives, which would take a minimum of 10 hrs to enter tissue code A.

If you don't wait the 10 hrs, according to BSAC tables you'd have some residual nitrogen in your system when you start the remainder of the dives. You'd be in tissue group B or C when you start the other dives.

If you spent the rest of those dives at about 20ft (6m) you would be offgassing the residual nitrogen, at about 30 ft you'd be adding nitrogen to your system (albeit very slowly).

However in all practicality I personally wouldn't worry about doing multiple dives at the depth you mentioned. For an added degree of safety i'd stay at about 20 ft.
Just my 2 cents.

Combined Surface interval table

Table A

 

[Spoon]

Interesting question Spoon.

Well strictly speaking they are time limits i.e (NDL limits) on dives to 12 meters (30 feet) however you'd need to be in the water for close to 4 hours on the first dive for this to be an issue.



However in all practicality I personally wouldn't worry about doing multiple dives at the depth you mentioned. For an added degree of safety i'd stay at about 20 ft.
Just my 2 cents.

yes i am aware that your ndls at this depth of 30ft are something like 300 mins. so technically i could have a couple of more dives with times of 30mins each in the bag while watching the ndl times closely and if i even stay shallower than 20ft i would be offgassing.

 

[Spoon]

However in all practicality I personally wouldn't worry about doing multiple dives at the depth you mentioned. For an added degree of safety i'd stay at about 20 ft.
Just my 2 cents.

actually i stayed in the region of 20-29 ft watching my depth gauge closely to make sure i wouldnt pass 30ft. whats weird was that at the end of dive 8, i actually felt better and less tired than my usual day of three dives (110, 90, 60ft )

 

[Jamdiver]

Sorry, should have read 9 meters = 30 feet

actually i stayed in the region of 20-29 ft watching my depth gauge closely to make sure i wouldnt pass 30ft. whats weird was that at the end of dive 8, i actually felt better and less tired than my usual day of three dives (110, 90, 60ft )

Actually that isn't that weird Spoon i've had similiar experiences, after a wreck dive to about 28 meters (93 feet) 36 min dive time, did a 5 minute safety stop at 20 feet for an added degree of safety.

Anyway I surfaced feeling kinda tired with a little bit of a headache, did a 2nd dive an hour l8r on another wreck at about 40 feet for 30 minutes. After surfacing from the 2nd dive I felt sooo much better it was like night and day.

Leads me to believe that the time spent shallow on the second time was in essence me offgassing the nitrogen from the second and first dive.