Is it ok to do 2 deeper dives following a shallow dive?

[s.s.seafan]

For all dives done from a boat in saltwater.... once you return to shore and remain on land for 15 minutes (or longer) all residual nitrogen instantaneously leaves your body and you are clear to dive again..

wow, that's totally news to me they didn't teach me that in the OW course... that really helps to put my mind to ease. thank you!

 

[dumpsterDiver]

wow, that's totally news to me they didn't teach me that in the OW course... that really helps to put my mind to ease. thank you!

You revert back to a virgin too, if it only "happened" on the boat.

 

[scubadiver888]

wow, that's totally news to me they didn't teach me that in the OW course... that really helps to put my mind to ease. thank you!

It isn't taught in the OW course. I've heard there is a pig, who flies, that teaches this. I was told by a unicorn that it only works half the time if you didn't hear it from the flying pig.

 

[boulderjohn]

Most the stats and tables are based on doing the deeper dive first. If just don't know as much about doing the shallow dive first. Could be fine. Could be more dangerous. Add to that, if you do it once it could be fine. If you do it 1000 days in a row it could be bad. Without stats, don't know what happens if you do it 500 days in a row. Probably not as dangerous as 1000 days in a row. Could be that it is fine even for 10,000 days in a row. We just don't know.

Add to all of this that what is fine for me might be bad for you. Original tables were created based on Navy divers. I am DEFINITELY not in the same shape as a Navy diver. This could mean the Navy tables are fine for Navy divers but not for me.

The PADI tables were created based on their own original research. They were not based on the Navy tables or Navy research. The 2001 international workshop that determined that there was no reason that you could not do the deeper dive after the shallower dive reviewed all available research before coming to that conclusion. That workshop did say that the deeper dive should still be done first in the case of deep technical diving, but that decision was not based on research. It was based on the insistence of a participant, Bruce Weinke (originator of the RGBM algorithm), who postulated problems for very deep dives based upon his theory of bubble mechanics.

also, a separate question, if a calculation shows the dive time exceeds NDL, does a 3 min safety stop at 15' remove the DCS risk completely (for dives less than 60' or 80' deep)?

The PADI tables do not include decompression. All surface intervals are based upon the diver having stayed within no decompression limits (NDLs). Consequently, if you violate the NDL on a dive, the tables do not have any way of helping you until you are clear and can start over. If you look at the back of your RDP the third paragraph in the left column tells you what to do in case you violate an NDL. The procedures are pretty severe because they have to get you cleared so you can use the table again.

The surface intervals are based on the amount of time it takes a specific theoretical tissue in your body to be clear of nitrogen. The concept is called half-times, and it is similar to half-life in radiation. The PADI RDP uses the 60 minute theoretical tissue for normal NDL dives. If you just barely exceed an NDL (less than 5 minutes), it requires you to clear that tissue, which takes 6 half-times--or 6 hours of surface interval before diving. If you violate by more than that, the rules play it totally safe and require you to stay out of the water for 24 hours so you can start over from scratch.

If you use a computer, it does have the ability to deal with decompression, so you don't have to wait until the table is cleared to get back in the water. The computer will calculate a safe surface interval for you.

 

[scubadiver888]

The PADI tables were created based on their own original research. They were not based on the Navy tables or Navy research. The 2001 international workshop that determined that there was no reason that you could not do the deeper dive after the shallower dive reviewed all available research before coming to that conclusion. That workshop did say that the deeper dive should still be done first in the case of deep technical diving, but that decision was not based on research. It was based on the insistence of a participant, Bruce Weinke (originator of the RGBM algorithm), who postulated problems for very deep dives based upon his theory of bubble mechanics.

Never said the PADI tables where based on the Navy tables but I guess if you read that into my message others might as well.

My point, and what you never addressed in your quote, is that the rules we learn in OW training are THEORY. Like most statistics, if you follow the rules then the statistics SHOULD apply to you but there are no guarantees. Additionally, if research, statistics and theory apply to doing deeper dives first this says nothing about doing shallow dives first. It just says that, according statistics, we know it is good to do deep dives first but we know nothing about doing shallow dives first.

I think the fact you read into my message something I didn't say or you focus on one thing which might be wrong, totally avoiding the main concept I was posting, is why many people come onto ScubaBoard - Scuba Diving Forum - Diving Social Network - ScubaBoard Home and find the place to be hostile or intimidating. It seems to send the message, post a perfect message or the moderators will feel the need to pick on what is wrong without acknowledging anything correct.

 

[k ellis]

I've heard there is a pig, who flies,.

Of course pigs fly. Never heard the swine flu

 

[boulderjohn]

Never said the PADI tables where based on the Navy tables but I guess if you read that into my message others might as well.

Sorry. Since this entire thread is based on using the PADI tables, I somehow thought that when you wrote "Original tables were created based on Navy divers. I am DEFINITELY not in the same shape as a Navy diver. This could mean the Navy tables are fine for Navy divers but not for me" you were talking about the same tables everyone else was. My mistake.

My point, and what you never addressed in your quote, is that the rules we learn in OW training are THEORY. Like most statistics, if you follow the rules then the statistics SHOULD apply to you but there are no guarantees. Additionally, if research, statistics and theory apply to doing deeper dives first this says nothing about doing shallow dives first. It just says that, according statistics, we know it is good to do deep dives first but we know nothing about doing shallow dives first.

I believe I did address that point, apparently not clearly enough. When I said that the international workshop that investigated this in 2001 reviewed all available research before deciding that there was no safety issue precluding doing the shallower dive first, I thought the implication that there was more involved than you suggested. I was simply adding clarifying information to your post.

I think the fact you read into my message something I didn't say or you focus on one thing which might be wrong, totally avoiding the main concept I was posting, is why many people come onto ScubaBoard - Scuba Diving Forum - Diving Social Network - ScubaBoard Home and find the place to be hostile or intimidating. It seems to send the message, post a perfect message or the moderators will feel the need to pick on what is wrong without acknowledging anything correct.

I am sorry you feel my response was hostile. It was not intended to be. It was intended to correct what I perceived to be misinformation, as I indicated above. Even if I misread the intent of your statement, as you said others might have misunderstood as well, in which case I succeeded in correcting their misconception. My post was further intended to add additional helpful information regarding the thinking that went into the 2001 conference, information that was missing in the thread and which I thought would shed more light on your comments.

If you see such replies to your post as hostile, I do regret that. The written medium is such that if one is not very careful with wording, then intent can be misconstrued. This becomes especially problematic when one wants to respond to a post that appears to contain misinformation or incomplete information. For my failure to use more gentle wording, I apologize. On the other hand, if your post was intended to mean that you are looking for a forum in which everyone agrees with everything everyone else says and never posts anything but pats on the back, then this is not the place to be.