Nitrox course. What's the point?

[lermontov]

That’s not true. The computer doesn’t really care what type of water it is in. It only cares about the pressure. In MOD, that’s all that really matters as well. The formulas for calculating MOD are translated to distance so that they will be more meaningful to us. Pressure isn’t really a measure we can visualize well.

The only thing that would be different if you set the wrong salinity is that the depth displayed will be different compared to the actual. But, then again, the depth displayed is just an estimation assuming constant atmospheric (and water) pressure.

the easy solution is something ccr divers adhere to religiously - always know your PO2
caveat: its true about its also a little joke

 

[EFX]

Getting back to the OP's question: "Nitrox course. What's the point?" The point is, as others have mentioned already, it gives you a cert enabling you to rent and/or fill tanks with nitrox. The O2% being anywhere between 22 and 40% for recreational divers. The advantage that is stated most often is that it gives you more dive time when doing multiple dives per day and/or multiple days of diving for the same depth and surface interval with air, assuming your dives are NDL limited and not gas limited. Two of the best known scenarios are diving from live-aboards or shore diving at a resort.

There is another scenario I ran into when I signed up to do a 3 tank dive with Jupiter dive center in Jupiter, Florida. All dives were drift dives over the reef in about an average depth of 75 feet from a boat. There were two dives in the morning, then lunch, then a third dive in the afternoon. They insisted that in order to do all three dives you had to dive Nx36. You could get on the boat as an air diver but you were restricted to doing only the first two dives. So, having the nitrox cert gives you options you wouldn't have otherwise.

I would recommend taking the class only course. Some agencies offer dives with it but you will pay more and learn nothing additional. Assembling your equipment on a nitrox tank is no different than assembling the equipment on an air tank. Underwater, you will feel no different breathing nitrox than air -- the mechanics of breathing are the same. Some divers say they feel better post-dive after diving nitrox as opposed to air but others say it doesn't make any difference.

 

[ToneNQ]

You are right. I am wondering if I will learn anything more in Nitrox course than in Science of Diving that I have already taken. I can calculate PPO2, know the limitations, understand Oxygen clean and service, know if equipment are compatible. It seems to me that I have already learnt all the theory and Nitrox course is almost 100% theory only.

You've learned the concepts, its not certain you have learned the theory. None of it is rocket-science, things like Equivalent Air Depth aren't even overly useful. But it all has a purpose and someday, you'll need EAD just like MOD. I'm curious as to why you were watching MOD on your deep course, its not a vaguely relevant diving NDL on air. I expect you might have a bit to learn about MOD. There is a good chance you know enough, but I expect you'll know more and you'll know it better if you looked at all of those theories as an EAN diver, rather than a broadly interested diver. There are aspects to each piece of theory that are not relevant to some types of diving, so those things are only taught in the diving that is relevant. I had to do two dives with my Nitrox, they were additional cost to the course and they were required to get certified. The dives are easy, but its doing your pre-dive routine with extra steps, and its wise to have competent supervision the first time you do something.

If you really have mastered all of the theory, talk to your instructor. I did Solo last year, normally some eLearning, classroom instructor work and a few dives. eLearning was unavoidable but it was also easy, so I just did it. For the classroom stuff, because I already have Sidemount we didn't have to reinvent the wheel with how to sling a pony bottle and manage a second air source underwater. Because I have a few tech certs, we didn't have to reinvent the wheel regarding how to carry and use equipment redundancy. But we still did the dives and he still put me through a few scenarios that were new to me. Its pretty rare that your instructor won't know something that you know, so talk to them, see what you can come up with. If you want the cert you have to demonstrate competence, if you don't want the cert then put the effort into something that you do want.

 

[ToneNQ]

I said half a joke, not 100%. Now, if you want to erect yourself as the Grand Master, bring it on. I believe that a dry suit does not give as much as freedom of movement than a wet suit. And it even have some additional training and safety constraints. You do question that? Fine. Then, I am sure that you will explain to us how a dry suit is much more convenient and has less safety requirement than a wet suit. I am waiting.

Its not an absolute question, there is no absolute answer. Water temperature is a key ingredient, and your tolerance to cold. A thick wetsuit takes an eternity to get on and greatly restrict movement, but there are some exotic ones that have less impact. I'd wear my drysuit over a 7mm any day of the week, I also think its more comfortable than a 3mm with extra insulators. A drysuit is far more comfortable to wear for surface intervals, and much better to put back on after that first dive when everyone on the boat is whimpering about how cold and miserable their wetsuit is.

Skills are different, risks are different, ballast is also different. I'd be hesitant to suggest one is safer than the other because its very dependent on the specific risk. I'm not going to detail the specifics because its a limitless scenario, and you're not going to understand some of the concepts as a newbie to diving. Also not all scenarios would be relevant to you, and as a recreational sport diver a wetsuit meets your needs superbly. You'll come around by yourself, or you never will, but they're expensive so you won't change your mind because of lobbying on SB.

 

[BRT]

delete

I didn't get quite that far so didn't have to delete.

 

[wetb4igetinthewater]

without the nitrox cert you cannot dive nitrox. no shop is gonna give you a tank fill without that card.

@peter_guy told me a story how he presented a trimix card and was turned down for nitrox. He then asked for trimix, but without helium. lol

 

[lermontov]

@peter_guy told me a story how he presented a trimix card and was turned down for nitrox. He then asked for trimix, but without helium. lol

haha good one - "can you mix me a 32/01 please"

 

[Blackcrusader]

When you dive on air are you limited by NDL's or by gas?

Air is not my issue and even if diving with others using nitrox a lot of divers will not get close to NDL if staying say at 30m as they are not so good on air and would end up with a short 40 minute dive time. Nitrox limits depth so for deeper dives to 45m I do that on air. I dive with people using nitrox and even then they are the ones limited by consumption rather than NDL if they want to do an hours dive. Sometimes I will ride NDL on air say go to 40m stay at 3 mins to NDL back to 20m then get to 3 mins to NDL then ascend. I can do that on a single tank and get in an hours dive. So this is on AL80's at most dive centers in Asia. I find some people want to end the dive as they feel cold after an hour whereas I do not feel cold and I do not use a wet suit.

On vacation dives I am not riding NDL all the time. I may go deep for first part of the dive if I wanted to see something. My average max depth on last 250 dives is 26m. Deepest dive 45m and longest dive 93 minutes. One dive I exceeded NDL limits for a short time and cleared deco. Also a lot of vacation dive buddies are on air not nitrox. Some DM's are required to use Nitrox at least one dive per day if doing 3 dives a day. Lets say I decided to use Nitrox 32% and did a dive to 30m and stayed there for 35 minutes, my issue is not air the issue would be the dive buddy and air most would be very low already and would need to be shallower much earlier to do an hours dive. Sure if I wanted a shorter dive time with a dive buddy who uses more air. I like to get at least 55 - 65 mins on a dive but 90 mins if possible.

So take my longest dive... I could have used nitrox and had some more time at a wreck but it's a small wreck have been to before so just really wanted to dive without time restrictions on the total dive. Not many dive centers let you do 90 minute dives. As you can see I do a lot of dives where time is spent at shallower depths. Not many divers can do this dive for this time and finish with 50 bar on an AL 80. The dive shop owner and I have done this dive together and he can do around 65 - 70 mins to 50 bar. So he lets me and a DM guide do it without other divers. The DM guide is slightly better on air than I am. So for last 70 minutes of the dive we were around 15m depth.

 

[Blackcrusader]

Interesting. So, it is possible to safely do 4 dives a day on air.?

Perfectly safe if you are not pushing NDL limits for the whole dive or always going on deep dives. It's how I do my dive vacations. Normally 2 weeks and actually the most dives I did in a single vacation in less than 3 weeks was 58 dives.

 

[Blackcrusader]

Getting back to the OP's question: "Nitrox course. What's the point?" The point is, as others have mentioned already, it gives you a cert enabling you to rent and/or fill tanks with nitrox. The O2% being anywhere between 22 and 40% for recreational divers. The advantage that is stated most often is that it gives you more dive time when doing multiple dives per day and/or multiple days of diving for the same depth and surface interval with air, assuming your dives are NDL limited and not gas limited. Two of the best known scenarios are diving from live-aboards or shore diving at a resort.

Dody... Nitrox 32% means I get longer times to NDL and is better over repeated dives. However dive times still depend on your sac rate and how long you stay at depth. If I was using nitrox 32% staying at 30m depth for 24 minutes I do not exceed NDL and can ascend and finish the dive. If on air at 30m can stay for 15 minutes but that is then 0 NDL so for safety lets make it 12 minutes at 30m on air. Nitrox gives me longer time to stay deep. It does not change the sac rate. So on multiple dives where you want to go deep to 30m then you get longer times to NDL. Even when I dive with my friends are also good on gas consumption we do not push staying deep on our dives. Sometimes we use nitrox but leave our computers on 21%. Some DM guides will do this as well.