Question How to dive nitrox for the first time

[happy-diver]

If I'm doing a couple of shore dives I'll breathe nitrox100 driving between dive sites, like last Wednesday

 

[EFX]

If you are going to do only two dives for the day and you are not going to extend your bottom time nitrox probably isn't necessary. This is most common during DM group led dives. Where nitrox makes a big difference is when doing multiple dives a day (more than two) and especially when diving over multiple days. The accumulation of nitrogen will begin to limit your bottom time to stay within your NDL. This is common when diving at a resort or on a live-aboard. In these cases I highly recommend getting nitrox certified. Usually, it's class room training only -- no dives are needed. You will learn about oxygen toxicity, how to calculate MOD, and how to test your tank among other things.

 

[uncfnp]

Any responsible operator would not mix air and nitrox divers together.

It happens. In fact it is not uncommon around the Caribbean but fortunately these operators don’t require you to ascnd as a group so your bottom time is not restricted by air divers.

But this also just happened to us in Indonesia on a Raja Ampat liveaboard. There were two air divers and there were 4 to a group. Of course we were the couple grouped with the air divers. Fortunately they also did not require us to ascend as a group so Eric and I could continue the dive if the 2 air divers went up early.

 

[Blackcrusader]

If you are going to do only two dives for the day and you are not going to extend your bottom time nitrox probably isn't necessary. This is most common during DM group led dives. Where nitrox makes a big difference is when doing multiple dives a day (more than two) and especially when diving over multiple days. The accumulation of nitrogen will begin to limit your bottom time to stay within your NDL. This is common when diving at a resort or on a live-aboard. In these cases I highly recommend getting nitrox certified. Usually, it's class room training only -- no dives are needed. You will learn about oxygen toxicity, how to calculate MOD, and how to test your tank among other things.

Yup this is mostly true. Some divers only doing two dives decided not to use nitrox as the dive times were one hour and secondly some divers gas consumption means they would not make the 1 hour diving staying deeper as I did. Having a dive doing a 20m average depth for the dive you want to have decent gas consumption.

I had a fall on the dive boat and getting some bruising so for a few days in my last 5 diving days I only did the two morning dives. So for me the 32% was allowing me to have those dives staying deeper. Also as most dives we started down to 30m depth the divers on 21% needed to come shallower before me. I reallly liked pushing the NDL a bit to the point where probably by 30 minutes into the dive the guides and other divers were back at 15m while I was at 22m - 25m depth with both plenty of NDL and also plenty of gas. Having a very low SAC rate allows me to safely enjoy the dives not needing to worry about the amount of gas required. Conditions were really calm as well.

I've seen many divers on nitrox happy to be with a guide and other divers on 21% they are not bothered by having shallower dives. I've done this myself. I have never been at a dive op that required divers on nitrox not to dive with divers on 21% Groups divers with some on 21% and others on 32% happens everywhere. At some dive ops you only get 21% so all divers are on the same gas.

Then the NDL difference comes down to the DC and settings people are using.

 

[Nemrod]

I am of a mnd that many who dive an air setting on Nitrox simply do not understand how to set their computers. As I have been told several times after being asked "how you stay down so long" my answer was learning to be still, using Nitrox and setting my computer accordingly. Then I am told, "James, we are just not into the technical stuff" and the next dive both of their computers locked out.

I am thinking to begin to advocate this basically harmless practice. That way, me and the DM or my buddy or whoever is left can have often a good 20 minutes of wonderful diving and with no fins sticking ino the side of my frame. Again, priceless.

I am not advocating or bragging about this profile, it was 32% mix and I was back on deck with a solid 500+ psi with an adaptive 5 minute safety stop and a cautionary 40 foot pause (half average depth). It is a bad practice to ride the computer even knowing the deco obligation will clear on ascent. But, sometimes, there is something interesting, I had the gas and well, bad, bad, bad Nemrod . All the cool stuff shows up like right at the last minute dang it. I shot my own buoy at 40 feet and surfaced alone.

 

[Subcooled]

@KatieMac
You are fooled if you think you are reducing your nitrogen load by ascending a bit if coming close to it - well at least if we are speaking about 30m.

Actually you then may load more tissues to the max than if you do an honest dive - speaking from the model. Afaik there is some evidence that doing this increases the risk of a dcs hit.

And "extending" the safety stop has probably been a real deco stop.

Now, while I belive this answer was not in the correct place, the message is an important one and worth bringing up.

 

[Subcooled]

This is just not true in all cases. I routinely dive 32% and my buddy dives air. My bottom time is generally limited by volume not by his %O2. I dive 32% to reduce N2 loading and a clearer head. However, I always set my computer appropriately so alarms are real and actionable.

When I dive on nitrox 30,32,34 or even 40, and my dive buddy is on air we do this:

1. I declare the maximum depth (oxygen toxicity is the limiting factor over gas narcosis)
2. My dive buddy declares the dive time (his/her nitrogen load being the limiting factor)

Which ever condition is met first, will be respected.

This is a simplified model without overhead diving and all the complications that it infers.

 

[Subcooled]

Lets clarify up a few things

When you increase the O2 % in the breathing gas
1. you cannot go quite as deep
2. you can dve longer in the shallows

 

[happy-diver]

All the cool stuff shows up like right at the last minute dang it.

 

[34109411]

I got my nitrox cert in 2023 as a dry course at the end of a dive trip but haven't dove nitrox since yet. I want to try nitrox on my planned october trip to cebu (moalboal, oslob, malapascua) but honestly I don't think I remember much from the course.

I will certainly do a full review of the course materials before the trip which I think are still available because the cert was with SSI. However, from what little I do remember, apart from the theory and the science, nitrox doesn't change much "how" I dive except that I need to check the gas and set my computer to nitrox mode, right? If there's a lot more I should do in practice then I better shut up and go back to the first page of the textbook now, but I just want to get a basic sense of where I am at the moment. Thanks in advance!

read the book again.