Dive tables, decompression, and training dive

[HPT3]

During my recent open water certification, we desended to 60 ffw and on this short dive of 23 minutes when we ascended, we did NOT do a decompression safety stop. After passing the OW test, I'm still not clear about decompression. This is the way I understand it. On the NAUI air table a decompression safety stop is not necessary unless one exceeds the recommended dive time. For example, on a first dive to 100 fsw a diver can stay down for a maximum time of 22 minute WITHOUT any decompression stop, but if that diver exceeds that 22 minutes to 25 minutes they must do a mandatory stop at 15 feet for 5 minutes. If they were to stay down from 26 to 40 minutes they must decompress for 15 minutes. I do understand that a 3 minute stop is a SAFETY procedure and I will abide by that. What I do not understand is why in the HELL would they (instructors) teach all this and ignore this on a certification dive? This has confused the hell out of me and it's only been through my own reading that I finally get it. Or don't I ? :fury:

 

[Don Burke]

HPT3 once bubbled... During my recent open water certification, we desended to 60 ffw and on this short dive of 23 minutes when we ascented we did NOT do a decompression safety stop. After passing the OW test, I'm still not clear about decompression. This is the way I understand it. On the NAUI air table a decompression safety stop is not necessary unless one excites the recommended dive time. For example, on a first dive to 100 fsw a diver can stay down for a maximum time of 22 minute WITHOUT any decompression stop, but if that diver exceeds that 22 minutes to 25 minutes they must do a mendetor stop at 15 feet for 5 minutes. If they were to stay down from 26 to 40 minutes they must decompress for 15 minutes. I do understand that a 3 minute stop is a SAFETY procedure and I will abide by that. What I do not understand is why in the HELL would they (instructors) teach all this and agnor this on a certification dive? This has confused the hell out of me and it's only been through my own reading that I finally get it. Or don't I ? :fury:

What did your instructor say when you asked him about it?

 

[SeaJay]

That's pretty much what I was thinking.

HP, I'm afraid I couldn't answer your NAUI table question... I have not used them.

PADI tables - which are similar - I know, however... And I can tell you that the 3 minute "safety stop" isn't a requirement... It's a recommendation.

The other two are requirements. You NEED to do those.

At least, that's the story according to the PADI table.

The bottom line is that there are no tables that are going to ensure that you don't get bent. That is, there is no profile you can dive where the risk of DCS is zero. People do get bent while diving within the tables.

Confused yet? So are the rest of us.

DCS - or the risk of it - doesn't seem to be a "black and white issue." Instead, it's shades of gray, making it difficult to teach or understand.

The recommendations as of late is that if you do a dive below 60 feet, do a "safety stop." It's a good idea, and is recommended. Other than that, don't dive past your NDLs until you're trained to do so. If you blow your NDL while underwater, stick to the rules you were taught... 5 mins at 15 if you blew by less than 3 minutes, and 15 at 15 if you blew by more.

...So was your instructor wrong for not doing a safety stop on a deep (> 60 feet) dive, even though he was within NDL's? Well... No... It wasn't "wrong." He did miss a great opportunity, though, to show you guys the recommended safety procedure for "deep" dives.

 

[Pam_In_Paradise]

Congratulations HPT3 on questioning the lack of a safety stop on your certification dives. IMHO this is something that should be taught and practiced from the very beginning. Although your dive was not one that required a deco period, you should always do a safety stop at the end of every dive. Since each person is different and there are various factors that might predispose us to a DCS hit, this safety stop is just that - an extra bit of safety. I personally have several factors that cause me to not only take a 3 minute stop at 15 ft but I do an initial safety stop halfway from depth to surface. For example, if I dive to 100 ft ( I am advanced trained and experienced), I will do a 1 minute at 50 ft, 1 minute at 25 ft and then at least 3 minutes at 15 feet. If I have been diving repetitively, I will increase those times. I also go up very slowly. Don't despair - as you do your safety stop(s) look around you. Sometimes I see something more interesting while hanging there than I did at the bottom. Keep learning - your Open Water certification is just the beginning. Dive Safe and Enjoy!
Pam

 

[HPT3]

About asking my instructor, I figured they're the experts. If a safety stop wasn't needed then we go right up. Some experts???

 

[GoBlue!]

I may very well be wrong, but I thought that NAUI is now recommending that dives >= 60' should have a 1 min stop at 1/2 of max depth as well as the standard 15ft stop. Can't remember where I read this, though....can someone clarify?

(If this is the case, it seems that your instructors should have observed a 1 min stop at 30ft as well as the 15ft stop that is "recommended" for NDL diving.)

Jim

 

[Don Burke]

I tried to attach a GIF of the NAUI tables with no luck.

Here's a link:

http://www.naui.org/table1.htm

The stop appears to be mandatory.

 

[jbd]

are not mandatory. They are a procedure that allows some extra time for offgassing which reduces to some degree the overall risk of getting DCS.

If you stay in the limits of your dive tables and ascend slowly you can come straight to the surface without undue risk of injury.

NAUI has recently made the suggestion that for dives deeper than 40 feet the dive may make a stop at one half of the maximum depth for one minute and then make the customary stop at 15 feet for 2 minutes. This is based on the concept of what is sometimes known as the Pyle stops or deep stops.

For the 60 foot dive mentioned at the beginning the divers had 3 completely acceptable options.

1. Ascend at 30 feet per minute straight to the surface.

2. Ascend at 30 feet per minute to 15 feet and do the 3 minute safety stop and then ascend at 30 feet per minute to the surface

3. Ascend at 30 feet per minute to 30 feet and stop for 1 minute. continue the ascent to 15 feet and stop for 2 minutes and then continue the ascent to the surface.

I agree that safety stops can be an enjoyable part of the dive. It gives you time to practice hovering skills and also gives you time to look at the minute creatures floating in the water column.

Mandatory decompression stops are quite a bit different than safety stops. Screwing up a mandatory stop will either guarantee that you will get DCS or it will significantly increase your risk of getting DCS.

 

[CincyBengalsFan]

Other table resources can be found through these links

http://www.ssl.umd.edu/projects/ControlStation/Personal/SCUBA/DiveTables/Navy_Tables.html


http://www.reefscuba.com/navytables.htm


http://www.flash.net/~table/table/p0000065.htm


http://divemar.com/NAUI/docs/articleshortfrm.html

 

[Don Burke]

jbd once bubbled... are not mandatory. They are a procedure that allows some extra time for offgassing which reduces to some degree the overall risk of getting DCS.

If you stay in the limits of your dive tables and ascend slowly you can come straight to the surface without undue risk of injury.

NAUI has recently made the suggestion that for dives deeper than 40 feet the dive may make a stop at one half of the maximum depth for one minute and then make the customary stop at 15 feet for 2 minutes. This is based on the concept of what is sometimes known as the Pyle stops or deep stops.

For the 60 foot dive mentioned at the beginning the divers had 3 completely acceptable options.

1. Ascend at 30 feet per minute straight to the surface.

2. Ascend at 30 feet per minute to 15 feet and do the 3 minute safety stop and then ascend at 30 feet per minute to the surface

3. Ascend at 30 feet per minute to 30 feet and stop for 1 minute. continue the ascent to 15 feet and stop for 2 minutes and then continue the ascent to the surface.

I agree that safety stops can be an enjoyable part of the dive. It gives you time to practice hovering skills and also gives you time to look at the minute creatures floating in the water column.

Mandatory decompression stops are quite a bit different than safety stops. Screwing up a mandatory stop will either guarantee that you will get DCS or it will significantly increase your risk of getting DCS.

Somehow I read the original post as 100 feet.

I agree with you.