Question How to dive nitrox for the first time

[lowwall]

So what it's common, you keep saying that as if because it's done that way often, it's somehow beneficial. It's not, at least to the diver who is paying for Nitrox and took the course so he or she can use it.

It's not about survival it's about longer, more enjoyable dives.

Of course there's a need to dive with a buddy who is on Nitrox, otherwise you're going to get a shorter bottom time than you paid for. Whether or not there are "mixed air/nitrox groups all the time" doesn't mean it's a good idea. Because it's not. No different than a dive charter that forces a diver to team up with an instabuddy of unknown skills, health, experience, etc because the charter doesn't want to pay a crewmember to do it.

Your argument is based on assumptions about the freedom to dive your own profile that do not necessarily reflect the realities of many (most?) actual dives.

A large percentage of the dives made in the world today are led by DMs, require the divers stay in fairly close contact, have a fixed time limit, and follow a profile that stays far from MOD for any nitrox divers and from NDL for any air divers. For these dives it truly doesn't matter if one buddy is on nitrox and the other on air.

 

[KenE]

Of course there's a need to dive with a buddy who is on Nitrox,

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.

 

[Nemrod]

Sorry, running an air profile while diving nitrox is simply not the right thing to do. Many good reasons have already been posted.

You do not always have the option to "shallow up" when the profile is relatively square such as on a reef drift dive, on a wreck, or simply if the topography is deeper.

An adaptive safety stop does not help you when diving an air profile on nitrox. it only reflects that you came relatively close to your air NDL or exceeded a certain depth.

There are many better ways to increase your safety while diving nitrox. You could stay farther away from you your NDL or you could set the computer to a more conservative setting.

Out of interest, what computer do you dive and what settings do you use? The adaptive safety stop makes me think it may be a Shearwater, not sure if other brands also run this.

Amen, exactly. Divers who do this simply do not fully understand. But it is okay, all we can do explain why it is not a good idea and then grownups have to decide for themselves. It is a bad practice though not necessarily a dangerous one. But it can be.

Dinosaurs breathed Nitrox, I wonder what they set their computers too. Oh, wait, extinction!

 

[gamon]

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.

Ok that's fair. High gas consumption can negate the potential extended bottom times provided with Nitrox.

 

[gamon]

Your argument is based on assumptions about the freedom to dive your own profile that do not necessarily reflect the realities of many (most?) actual dives.

A large percentage of the dives made in the world today are led by DMs, require the divers stay in fairly close contact, have a fixed time limit, and follow a profile that stays far from MOD for any nitrox divers and from NDL for any air divers. For these dives it truly doesn't matter if one buddy is on nitrox and the other on air.

Right. If it's a mixed gas group led by a DM and all divers must surface together, and do the same surface intervals then Nitrox is almost pointless.

 

[uncfnp]

Hi @KatieMac I understand what you are saying and I know others that do this as well. Many years ago this too was recommended to me by medical dive professionals as a way to lower my risk. But I think this practice is now largely obsolete with modern dive computers that have conservative settings.

As previously stated, unless you have an older computer that doesn’t have conservative settings, you are wiser to set your dive computer for your actual nitrox percentage.

 

[boulderjohn]

Many years ago this too was recommended to me by medical dive professionals as a way to lower my risk. But I think this practice is now largely obsolete with modern dive computers that have conservative settings.

I never thought it made any sense.

I think it's prevalence is at least partially true to Dive Training magazine, which had at least two articles by editor Alex Brylske that essentially said that divers had two (and only two) choices for using a computer with nitrox: 1) dive with limits set for air for greater safety or 2) dive with it set to the accurate nitrox mix for extended bottom time, in which case he evidently assumed that you had no choice but to dive to the full no decompression limits for that nitrox mix. He didn't actually say that, but in his explanation, he pointed out that there was essentially no safety difference between diving to the NDLs for air and diving to the NDLs for nitrox. Stopping somewhere in between was not an option.

Alex was (and still is) a brilliant man, a true pioneer in the world of diving. He wrote the Encyclopedia of Recreational Diving. But he was simply wrong on this, and he led a lot of people astray.

PS: I wrote to Dive Training magazine after one of those articles. I never got a reply.

 

[lowwall]

Right. If it's a mixed gas group led by a DM and all divers must surface together, and do the same surface intervals then Nitrox is almost pointless.

Certainly true when it comes to single dive DCS risk. But you might want to use Nitrox anyway if this is one of many dives you are doing in a short time. Or if you believe it helps with subclinical side effects of diving such as fatigue.

 

[lowwall]

Dinosaurs breathed Nitrox, I wonder what they set their computers too. Oh, wait, extinction!

According to a reliable resource, it was carbon monoxide poisoning (and maybe cancer) that caused it, not DCS.

 

[NothingClever]

Diving nitrox with the computer set to air adds a safety margin.

Seriously, who taught you this?

I’m not asking for a specific name, but was this a technique you got from an instructor, a dive buddy or something heard in resort chatter?