Remember when Nitrogen Narcosis was called Martini's Law? The theory goes that the narcotic effect of nitrogen is similar to consuming one martini for every 33 ft of depth. So if you dive to 33 ft., you feel as if you'd had one martini, 66 ft would be equivalent to two martinis, 99 ft, three martinis and so on. It sounds silly now, but it sounded reasonable when Lloyd Bridges said it on the television show Seahunt.
Our knowledge of Nitrogen Narcosis and its effect has grown a little since "Martini's Law," and one of the most profound advances was the realization that if we added helium to our breathing mix, we could limit the amount of nitrogen and hence manage our narcosis level. Mixed gas diving has been around for a long time in commercial applications, but it's only gotten popular in recreational/technical diving in the last 10 years or so. There are myriad diving courses teaching the use of helium mixes in various forms (trimix, triox, heliox, heliair, helitrox, ad nauseum) for use at various depths.
I would like to pose a question: at what depth here in the Great Lakes do you need to start adding helium to the mix? Traditionally, the entry level technical diving courses have taught the use of air or nitrox to a depth of about 150'. Students not comfortable diving air to that depth either have to limit their depth, or take a more advanced course like Trimix Diver to be able to utilize helium-based mixes. Do you think there is value in adding a module to the entry level courses, like Adv. Nitrox/Deco, that would cover using limited helium-based mixes. Many organizations offer such courses, I'm just wondering how many people see the value in making "trimix lite" available at the Adv. Nitrox/Deco level, or do you feel breathing air to 150' is fine and we should leave the helium alone until divers take the full Trimix Diver course?
1 comment:
Depending on the conditions, I think 150Ft is the point where narcosis comes into play. I got narc'd twice: once in Cozumel and I swear I had no idea what was going on...too long in the water and too deep evidently for my constitution. I thought I had finally become one with the ocean down below 150Ft!......the 7 other divers waving at me from 100 Ft above me didn't even trigger any questions on my part.....The second time was on the Miller Lite in Fort Lauderdale. I knew instantly I was narc'd and went up 4 Ft to de-narc. It worked. I have never been narc'd ever since, probably because I now dive Trimix. It is expensive and I usually dive below 200Ft when I use it, but I also have many dives on the Hydro Atlantic around 150FSW on 21/35. Back to the subject: IANTD has a good program that includes Helium for these depths. TDI is more old fashioned in that way and so am I.
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