Only on ScubaBoard could we take a simple, straightforward question, especially in the Basic Scuba sub-forum, and completely careen off the rails with absolutely asinine answers and techniques.
Question How to dive nitrox for the first time
- Thread starter ttc008
- Start date
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I just checked the SSI Instructor Manual for Nitrox, and under "The Benefits of Breathing Less NIitroge", under "Nitrox use and Decompression Sickness" it lists. "Setting your computer for EAN21 (or using air tables) increases safety margin".
It goes on later to say "While treating nitrox as though it were air. may somewhat reduce the risk of decompression sickness, it does not eliminate it. Additionally, divers who treat nitrox as air must still keep their exposure to elevated partial pressures of oxygen within acceptable limits." There's a couple of other things listed on why you might want do dive an Air setting with Nitrox.
The student book has similar verbiage too.
Thanks for the detailed points. Can you also talk a bit about what’s normally going to happen in the dive shop on the day and where do I start?- Check that the gas analyser is calibrated, calibrate it if needed
- Analyse your gas
- Calculate your MOD
- Correctly label your cylinder with MOD, gas mix, your name
- Plan your dive - you will now be limited by gas, not just NDL/no-stop times
- Discuss with your buddy what gas are they diving (hopefully similar gas mix, if they are on air and you use nitrox, change your buddy)
- Set computer(s) to correct gas mix
Repeat each day
Like is the DM going to lead me to my tank and give me an analyzer so that I can do the checking?
The places I’m going to, Moalboal, Oslob, Malapascua, are all touristy sites and will probably be very busy. Do you have other practical suggestions for me to make sure everything is ready to go before we get in the water/on the boat?
Thanks again!
Each boat/shop will have their own standard procedure. Not specific to your trip but typically the shop will analyze and mark the tank after they fill it. There should also be a log book. You then confirm the gas and sign the log. Some divers don’t personally check their tank. Others will watch as staff uses the analyzer. Other times the diver themselves will use the analyzer. The unit is usually nearby but other times you will have to ask for it.
If you choose to use the analyzer make sure you know how. An inaccurate reading is not much better than no reading. And sensors can be easy to damage and expensive to replace. Plus different analyzers operate a bit differently. Get the staff to demonstrate before you try.
...some places will have an analyzer station set up somewhere and point you to it. It's unlikely that they would have staff accompany a certified (nitrox) diver, but if you ask for help they probably would send someone to help you out. Couple of places I've seen will have analyzer info in an Intro video that you can watch before you get there, or possibly may do so as part of their intake process.
I think I have seen every procedure imaginable. The one you don't want to accept is the one where they tell you what is in the tank and expect you to accept it without checking it. I have had that happen more than a few times, and I simply tell them I want to check it myself. They always produce an analyzer.
Blackcrusader
Contributor
Dives on the walls in Moalboal and also at Pescodore island do go to 40m for recreational divers.
Some guides do prefer not to exceed 30m on dives depending on the dive op. I have done many dives 35-40m depth in Moalboal. I was there for two weeks in February and again two weeks in March this year.
When I dive on 32% I set I try to limit my depth to 30m and do not push the MOD of 34m.
On most my dives the guides and other divers were on 21%. This just meant that as they needed to ascend due to NDL I would just continue the dive at around 20m depth or a bit deeper and then ascend near the end of the dive. This let me enjoy being on my own chilling out with the other divers just above me.
@ttc008 When you ask for Nitrox you need to analize the gas mix on your tank and make sure you set your DC to that mix. Always check the mix yourself. In fact where I was diving with Savedra in Moalboal you cannot take a nitrox tank without you first checking the mix in front of the staff, and writing the date, your name, cert level, gas mix and gas tank pressure in the shops nitrox log book. Then the tank was labeled with your name and the had mix on it. Although 32% is the standard mix sometimes you get 31.5% but you can also ask for 40% or 25%
Nitrox just allows you to stay deeper for longer but that means using more gas. It won't give you a longer total dive time. Recently I was diving where the dive op sets dives times at 60 minutes with 90 minute surface intervals between the morning dives and a 2 hour interval before the afternoon dive.
I am an experienced diver and use less gas than even the guides I was diving with. So I am about to utilize my nitrox mix and only ascend to a shallower depth when my NDL was at around 2 minutes.
Do pay attention to your SPG and to your NDL and enjoy your fun dives. Also upload your dive logs so you can review them after dives.
Blackcrusader
Contributor
Why would your buddy shoot to the surface and end the dive just because they had 1 or a few minutes of Deco time on their DC? Deco obligation will clear on the dive as they ascend to shallower depths without needing to end the dive. Of course better not to have unplanned deco and also be trained for deco and understand your DC as well.
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