Exceeding maximum dive time?

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kat.hayes

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Just started my certification course and am wondering about the following:

1. Using Naui dive tables, what happens if you stay longer than the maximum dive time you are supposed to stay without a deco stop? As an example, what if you go down 60-ft and go beyond the maximum dive time of 55 minutes to, say 65 minutes? Is this dangerous or does it mean you just need a longer deco stop?

2. What about on your second dive if you go beyond the adjusted maximum dive time (AMDT)?
 
Just started my certification course and am wondering about the following:

1. Using Naui dive tables, what happens if you stay longer than the maximum dive time you are supposed to stay without a deco stop? As an example, what if you go down 60-ft and go beyond the maximum dive time of 55 minutes to, say 65 minutes? Is this dangerous or does it mean you just need a longer deco stop?

2. What about on your second dive if you go beyond the adjusted maximum dive time (AMDT)?

These are good questions, but should be answered by your instructor. The internet is a great place to discuss diving protocols, but one should be careful to take the answers with a grain of salt.

Let us know what your instructor tells you! :eyebrow:
 
If you exceed the maximum no-decompression time, you increase the risk of an attack of DCS. This risk can be reduced with a decompression stop of appropriate length, assuming you have sufficient air to complete one. The same is true of your second dive. This will be covered in your course. Decompression dive are generally considered advanced dives.
 
i am also interested in this question. perhaps an instructor or tech-diver here can give some quick pointers?
 
Here's the thing. Decompression diving is not something a person should learn on the internet.

With that said, decompression stops depend on the time at depth and the gasses carried, plus the method of calculation of your deco profile. For anyone really interested, you can download a free trial version of V-Planner and pop in the numbers and play with it yourself until your heart's content.
 
While I generally agree with Rick, I think this is a sufficiently basic question that a more responsive answer is warranted and dpbishop has provided that. I disagree only with the bit about "assuming you have sufficient air to complete one." In that regard, a decompression stop of the appropriate length will, in theory, reduce the risk of decompression sickness (bends). If you do not have sufficient air, then you cannot do one and have an increased risk of DCS.

There is rarely a reason a new diver should exceed the times given in the tables. (I never say never.)
 
Don't know the NAUI tables, but the PADI tables have on them emergency decompression instructions for overstaying your welcome at your particular depth.

Two pieces of advice:

One. Ask your instructor.

Two. Don't press the NCD limits.
 
Back in the day when I took the class, it was stressed.... Plan your dive, then DIVE THE PLAN.

Most tables are only a guide, and just because they say you "can" make the dive, that doesn't mean you "should" make the dive. It never hurts to go a little conservative.

I don't know how NAUI handles accidental overruns on table based dives, but my guess is your instructor does, ask. Oftentimes it's easy to get excited about the class and start asking questions that'll be answered later in the course, I wouldn't get too far ahead of yourself just yet.
 
The basic assumption behind no-stop tables is that, during your dive, if you have any issues, a direct (but controlled) ascent to the surface is an acceptable solution. Once you exceed no-stop times, that direct ascent becomes a more and more hazardous option, and your risk of getting hurt by doing a direct ascent increases steadily.
 
Just started my certification course and am wondering about the following:

1. Using Naui dive tables, what happens if you stay longer than the maximum dive time you are supposed to stay without a deco stop? As an example, what if you go down 60-ft and go beyond the maximum dive time of 55 minutes to, say 65 minutes? Is this dangerous or does it mean you just need a longer deco stop?

Since you are using NAUI tables, a certain amount of deco information is provided. The MDT (NDL to PADI divers) is 55 minutes for 60' However, if you overstay to 80 minutes you MUST make a 7 minute stop at 15'. This stop is MANDATORY.

Recreational diving is based on the concept of a direct ascent to the surface at any time. A mandatory deco stop moves the dive outside recreational concepts.

Is it dangerous to use the NAUI tables exactly as given? I doubt it! If it was significantly more dangerous, the tables would have been revised years ago. As far as I know, the 1989 edition is the most current version and it requires an ascent rate of 30 fpm while PADI still allows 60 fpm.

Every agency is recommending a 3 minute safety stop at 15 feet. But the safety stop is not mandatory. Those deco entries on the NAUI table ARE mandatory. Skip them and you will very likely wind up in a chamber.

There is also a significant difference in how bottom time is measured. For NAUI, it is the time between descending from the surface and ascending back to and reaching the surface. The entire round trip. Obviously, it doesn't include the mandatory deco time (although the tables don't say that). Since you can only ascend at 30 fpm, you need to cut 2 minutes off the MDT of a 60' dive so you are back to the surface on time. You really have just 53 minutes from the time you leave the surface until you must begin your ascent for the first (non-repetitive) dive.

2. What about on your second dive if you go beyond the adjusted maximum dive time (AMDT)?

Even with the extended bottom times and mandatory deco, you still wind up with a letter group. There is no change in the procedure, you just do the surface interval and plan the next dive.

You should be discussing this with your instructor. Most of the folks around here are working with the PADI tables and NAUI concepts are different.

Ask your instructor. Don't rely on a single word I have typed. If you mess this up, you will wind up in a chamber or paralyzed or dead.

Personally, I never went beyond the MDT. I never wanted to test the deco entries.

Richard
 
https://www.shearwater.com/products/swift/

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