Diving shallow on Nitrox.

[NAM001]

The analysis I read said that O2 is actually more narcotic than N2, but because some of it is metabolized, that brings its overall effect to be very close to that of N2.

Archer are you talking about narcotic in the recreational range or the tech depth ranges. I ask this because it is (I assume) true tat O2 is narcotic however IF it does not become disabling narcotic till ie 200 ft then it is a non worry issue at <100 ft. Millions of divers use nitrox to 140 all the time and if you dive air you are diving nitrox by definition. folks are deep diving air to 200 ft. At some point all gassed take their toll as the PP of that gas increases. Our bodies are geared to run on PPO2 of .21 +/- yet we by application push it to 1.4 and above without consequence. Also time has to be a factor in the exposure at those PPO2's. A hospital bed with a O2 tent will get you after a period of time and there are protocols to prevent that. In diving we use trimix to manage those factors. We insert a replacement gas that is not narcotic in the depth ranges we are using them at. Ill make this up but He may be narcotic below 1000 ft, so at 200 ft its a non issue.

 

[NAM001]

You really should be sure you're putting oxygen-compatible air in a nitrox-labeled tank, to ensure you don't get crap in the tank. My shop's fill rig has an extra filter on the side where they make nitrox, and that's also what they use for filling tanks labeled nitrox, with air.

Here is a question to ask yourself. how long did the folks that started diving nitrox dive with regular air with no problems till some scientist said you could have a problem under the right conditions. IMO the problem is not the O2 being put into a tank. Its the O2 being put in a oil contaminated tank. that occurs over a long period with reasonable fill stations. If one fill station develops a major problem and is not detected early it can happen in minutes.. A station with a problem only takes one fill to contaminate. I have 2 lp95's that came from a vip with rust in them. They were 1 year old and only filled by one fill system. when the shop closed i got one of the compressors and filters systems. the filters were plumbed backwards. moisture separators had compressor air going into the top and out the bottom blowing moisture into the fill line. That line filled a tank directly of a single 4500 cascade tank. Those filters were military filters and looked like perhaps 18" long bullets with a decsicant filter cartridge in them. I probably got a direct fill one time and that did it. One year later the tank had rust blotches and no water in the tank. What ever water was in there was blown out during nonrmal use or empting.

 

[mi000ke]

Just got nitrox certified last week. Did my first dive of day - deep wall - on nitrox 32. Second dive was 60' reef after 50 min SI. Thought I'd save a few dollars and go air on the second dive. Ended up having to come up to 40' for last 15 min to keep my (admittedly conservative) Cressi computer from going into deco. I did nitrox on all the dives - deep and shallow - after that. Did not notice any difference being on nitrox. But when diving at 7:30 am, I feel like sh*t no matter what.

 

[archer1960]

Here is a question to ask yourself. how long did the folks that started diving nitrox dive with regular air with no problems till some scientist said you could have a problem under the right conditions. IMO the problem is not the O2 being put into a tank. Its the O2 being put in a oil contaminated tank. that occurs over a long period with reasonable fill stations. If one fill station develops a major problem and is not detected early it can happen in minutes.. A station with a problem only takes one fill to contaminate. I have 2 lp95's that came from a vip with rust in them. They were 1 year old and only filled by one fill system. when the shop closed i got one of the compressors and filters systems. the filters were plumbed backwards. moisture separators had compressor air going into the top and out the bottom blowing moisture into the fill line. That line filled a tank directly of a single 4500 cascade tank. Those filters were military filters and looked like perhaps 18" long bullets with a decsicant filter cartridge in them. I probably got a direct fill one time and that did it. One year later the tank had rust blotches and no water in the tank. What ever water was in there was blown out during nonrmal use or empting.

Yeah, if things aren't built or operated properly, you can be screwed in a hurry.

 

[archer1960]

Archer are you talking about narcotic in the recreational range or the tech depth ranges. I ask this because it is (I assume) true tat O2 is narcotic however IF it does not become disabling narcotic till ie 200 ft then it is a non worry issue at <100 ft. Millions of divers use nitrox to 140 all the time and if you dive air you are diving nitrox by definition. folks are deep diving air to 200 ft. At some point all gassed take their toll as the PP of that gas increases. Our bodies are geared to run on PPO2 of .21 +/- yet we by application push it to 1.4 and above without consequence. Also time has to be a factor in the exposure at those PPO2's. A hospital bed with a O2 tent will get you after a period of time and there are protocols to prevent that. In diving we use trimix to manage those factors. We insert a replacement gas that is not narcotic in the depth ranges we are using them at. Ill make this up but He may be narcotic below 1000 ft, so at 200 ft its a non issue.

The article didn't go into a ton of detail, but the impression I got was that the narcotic effect was based on the molecular weight, which for 02 is 32, and N2 is 28, so they're pretty close, and the metabolism of O2 reduces its effect slightly. CO2 is 44, which is why it's much more narcotic than the others. Helium's molecular weight is 4, so it's much less narcotic, but has other effects.

 

[Storker]

the impression I got was that the narcotic effect was based on the molecular weight

Only if you do some serious cherry-picking of the data. There seems to be a correlation between lipid solubility and narcotic effect, but none between molecular mass and narcotic effect.

Carbon Dioxide, Narcosis, and Diving | Global Underwater Explorers

 

[archer1960]

Only if you do some serious cherry-picking of the data. There seems to be a correlation between lipid solubility and narcotic effect, but none between molecular mass and narcotic effect.

Carbon Dioxide, Narcosis, and Diving | Global Underwater Explorers

I didn't intend to cherry-pick; it was a brain fart on my part. You're correct, and I was remembering wrong.

 

[tarponchik]

Here is another thought after my recent experience. On a 50-90 ft boat dive, everyone including the DMs was going on NITROX. So, silly me, I did not want to ruin the party. I am trying to be a team player sometimes, so asked for NITROX too.

We jumped into water with 2 DMs, one leading, and one guarding our backs. The DMs signal thumbs down, so down we go with DM #1 and wait for 10 min at the mooring anchor for the rest of the group with DM #2 cause someone could not sink. Finally, we start cruising but it goes on for just another 25 min; then the DMs started banging their tanks cause everybody was running out of air already. So I go up to safety stop with 1,200 PSI and 10 min time at 65 ft left.

Will I do this again? With random divers in the group, probably not. They will likely run out of NITROX before I run out of my NDC limit on air.

 

[tridacna]

But...you "felt" so much better after the dive.

 

[Diver-Drex]

Here is another thought after my recent experience. On a 50-90 ft boat dive, everyone including the DMs was going on NITROX. So, silly me, I did not want to ruin the party. I am trying to be a team player sometimes, so asked for NITROX too.

We jumped into water with 2 DMs, one leading, and one guarding our backs. The DMs signal thumbs down, so down we go with DM #1 and wait for 10 min at the mooring anchor for the rest of the group with DM #2 cause someone could not sink. Finally, we start cruising but it goes on for just another 25 min; then the DMs started banging their tanks cause everybody was running out of air already. So I go up to safety stop with 1,200 PSI and 10 min time at 65 ft left.

Will I do this again? With random divers in the group, probably not. They will likely run out of NITROX before I run out of my NDC limit on air.

EAN decreases nitrogen uptake during dives. You can use that fact to increase bottom times or decrease decompression stress. I'm not sure how decreasing inert gas loading and decompression stress has a downside?