Safe and Unsafe

[trueno]

I am a Dive Master through NAUI. I am recently in the process of helping an Instructor with an Open Water class. I was asked to teach the NAUI Dive Tables and so I did. But at the end of the lesson I was pulled aside and was told if I am going to teach dive tables, I need to teach every thing, so I had asked what it was that I missed? The instructor explained that I need to talk about the flying aspect toward diving. I then asked him to elaberate and it was said to me that I needed to explain how we can fly after diving in a plain. I said to the instructor that I was taught not to fly after diving for 24hrs. NAUI say's after the first dive you shouldn't fly for 12hrs, and if you have a repetitive dive day, you shouldn't fly for 24hrs. Now with this said. My question is, Why would I even mention the idea of flying is ok after diving? I don't know the specific numbers, but, I do know that the cabin pressure can change any where from 1000-10,000ft with in a ten minute time span. I do not consider this safe, in both knowledge or practical application. I would like feed back if anyone is willing to help?

 

[bleeb]

II don't know the specific numbers, but, I do know that the cabin pressure can change any where from 1000-10,000ft with in a ten minute time span. I do not consider this safe, in both knowledge or practical application.

Can you expand on reasons why you don't consider this safe? The standard commercial aircraft pressurization is 8000 ft, which is roughly equivalent to 0.78 ata IIRC. In other words, a pressure change of a little under 30% or 7 ft of water, which, while not insignificant, are both considerably less than what people experience in the majority of dives.

Another thing to consider is what exactly would you recommend to new students with respect to flying after diving. I don't think you can get away without saying anything. They might assume there are no issues at all.

 

[SteveAD]

The point is not to teach that it is ok to fly after diving, rather when it is ok to fly. You have it right. The residual Nitrogen in the body can pose a DCS threat if the diver goes to a less than sea level with an elevated nitrogen level. The student needs to know this info. I think you may have simply had a miscommunication with your instructor. Did you teach the tables with NO MENTION of flying after diving rules? If so, that is what your presentation was lacking.

There is a hierarchy in a teaching situation. A DM certainly should not contradict an instructor in front of students, but the instructor should try to afford the DM the same courtesy. In the event that potentially dangerous misinformation is being passed the presentation should be stopped tactfully and discussed out of student earshot. Communication is always important. I always debrief my DM students and DMs after we work together critiqueing how they did as well as inviting question from them. Ask your instuctor questions and if you have more questions after his answer keep on asking them.

 

[ligersandtions]

Teaching students how to use the dive tables and teaching them about flying after diving are separate issues, imo. Granted, I understand that you will be teaching them about residual nitrogen when you are talking about the tables, and that is the concern when it comes to flying....but teaching a student how to use a dive table to plan a dive (or repetitive dives) has little to do with flying afterwards.

You should mention flying after diving; explain what it is that makes it a risky activity if done too soon after a dive (or multiple dives), and when it is okay to fly. If you have access, I know there are tables (this could tie it into the above discussion) that show your pressure group / residual nitrogen, planned flight altitude / cabin pressure, and how long you should wait after your dive before you fly based on the two criteria.

But I would say that you are not in the wrong for not mentioning flying after diving when you're teaching dive planning and tables. It should be discussed, but that is not the only time it can be done effectively.

 

[Diver0001]

My question is, Why would I even mention the idea of flying is ok after diving?

You teach it because it's the agency recommendation and you must teach it.

What I always say about flying after diving is that "waiting too long is impossible, flying too soon is. Be cautious and take these recommendations for what they're worth... the ABSOLUTE minimum."

In addtion to that, people you teach *will* go on diving holidays and they need to know how to deal with this.

R..

 

[masterof0]

My question is, Why would I even mention the idea of flying is ok after diving?

It is important to discuss issues like this because the people you are teaching don't know what they don't know. If you don't have this conversation with them, they won't give it the first thought and not realize that the is a "no fly time" following diving. (As I have come to learn this is not as much of a "no fly" time as it is a change - reduction - in atmospheric pressure including driving). As a DM/Instructor, you should error on the side of caution and over communicate when it comes to issues related to safety and health.

As a new diver, I can tell you that I certainly never would have given it a thought. This has held true to a lot of things I have learned over the course of the 6 months of my diving.

 

[covediver]

You teach about flying after diving because a lot of people fly off to places other than the pacific northwest in order to go diving in warmer water.

Why you would teach it in the context of something as narrow as how to use tables in beyond me. It is properly discussed in the context of RNT and the bends. Current precautionary practice is to limit altitude changes after diving and until current practice changes you are obliged to teach what current practice is (yes, it is a tautology, albeit a useful one in defining standard of care and training).

What does the instructor syllabus call for in that module and did the instructor provide that information when he asked you to talk about the tables? Sounds like the instructor wants to play, "bring me another rock, I don't like the one you brought me."

The 12- versus -24 hour offgasing margin has been around longer than I have been diving. I recall that it was repetitive group D when I was learning. I always like the 24 hour rule myself, because it gives me a time to relax and check out some of the above water attractions.

 

[Puffer Fish]

You teach about flying after diving because a lot of people fly off to places other than the pacific northwest in order to go diving in warmer water.

Why you would teach it in the context of something as narrow as how to use tables in beyond me. It is properly discussed in the context of RNT and the bends. Current precautionary practice is to limit altitude changes after diving and until current practice changes you are obliged to teach what current practice is (yes, it is a tautology, albeit a useful one in defining standard of care and training).

What does the instructor syllabus call for in that module and did the instructor provide that information when he asked you to talk about the tables? Sounds like the instructor wants to play, "bring me another rock, I don't like the one you brought me."

The 12- versus -24 hour offgasing margin has been around longer than I have been diving. I recall that it was repetitive group D when I was learning. I always like the 24 hour rule myself, because it gives me a time to relax and check out some of the above water attractions.

Thank you so very much. I was worried that the only message was one of flying... but go to Hawaii, dive in the morning and visit the top of a volcano can be a lot worse...

So, does anyone want to guess if the issue taking a hot shower or going in a hot tub after diving was also addressed?

 

[String]

Flying after diving is important as most divers dive on a holiday and most of those get there and back by plane so its important to teach them.

There are no hard and fast rules about flying and diving. Some agencies say 24hrs, some 16, some 12. Some insurance companies say different again and say 24 or even 48hrs.

If you actually do the maths using the altitude and transfer tables you can work out your own time if needed. Its something people need to be aware of, understand AND know how to calculate for themselves.
Its a good time to introduce the concept of altitude tables and cover the basics of those.

As for the pressure thing most commercial aircraft are pressurised to a cabin altitude of about 5500ft. It CAN in theory drift up to about 8000ft but very rarely these days. Therefore you can plan for that with altitude tables. The only real danger would be in the event of the aircraft losing cabin pressure but OTOH if that happens you may have more to worry about than being "a bit bent" and in any case you'd (i) be on oxygen and (ii) only for a few minutes while it descended.

 

[rstofer]

Not only should flying be discussed but so should altitude changes in general. For example, if you drive from sea level to a mountain lake at 6000 feet, you have some residual nitrogen before you ever get in the water.

How much? Well, I imagine it depends on how long it took to get there. Some dive computers, like the Dive Rite Nitek Duo, will calculate this for you. Others are less helpful.

From a tables point of view, you could be an H diver if you go to Lake Tahoe from Sacramento. See The Complete Guide To Boating Lake Tahoe: Diving, Dive Sites, Tips

This doesn't need to be discussed in great detail but, like flying, it should be mentioned as a consideration. The availability of an Altitude Diver course might be mentioned as well. Just in passing...

Richard