Question How to dive nitrox for the first time

[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?

 

[boulderjohn]

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.

I still usually use it. They used to call it Geezer Gas. I'm a geezer.

I generally try to avoid such dives to the greatest extent possible, but sometimes you have no choice. Unless it's super shallow, I'm doing the nitrox.

 

[arkstorm]

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?

I think it is also relevant to ask when this concept was taught because I seem to remember this idea being presented in the PADI EAN manual in the late 90's / early 2000's, i.e., prior to computers with conservativeness settings. I would agree that this concept is obsolete today.

 

[johndiver999]

I’d only make one set of numbers (your MOD) visible to others to thoroughly prevent confusing the dullard on the team (me).

In much smaller text, the cool kids put their O2 percentage down to the tenth on the neck of the cylinder as positive confirmation they’ve analyzed their gas.

So, if you’re diving a tank of 36% EANx, your tank will show:

29m / ttc008

And on the neck on a small label, you’ll write 35.9 (or whatever precise mixture your gas analyzer shows) and the date.

what are you talking about? ttc008 and what does 29 minutes mean?

I put the mix on the tank.

 

[boulderjohn]

what are you talking about? ttc008 and what does 29 minutes mean?

I put the mix on the tank.

I'm pretty sure it means an MOD of 29 meters.

 

[Nemrod]

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?

I have seen multiple instructors telling students to dive an air setting. Again, IMO, that alone is not especially dangerous but it gains nothing over setting your computer correctly, setting a comfortable (to you) gradient setting and then using the gray matter between the ears to say, hey, let's go up or shallow up or end the dive before approaching the NDL.

I have several times been on boats or at a dive locations where divers set for air and exceeded NDL and locked themselves out or pushed MOD depth.

I certainly can and do run hour plus dives on 80cf in that magic 60-100 feet zone. Tank volume is not for me (or many divers) the limiting factor, it is NDL.

I understand DCS is scary and inconvenient if it happens but I think that card is over played. Anecdotal, yes, but I have done thousands of dives and due to application of some common sense have never been bent. I have seen people get bent and they all did something really stupid and one fellow paid for it by spending his life in a wheel chair. Now that is inconvenient .