Question NITROX (in less than 40 foot of water)

[MaxBottomtime]

My local shop does not partial pressure blend and we can easily get higher than 40% with continuous blend (aka Nitrox Stick). I know another dive shop that uses a Membrane system and can easily fill to 38 to 40%.

Even 40% wouldn't be dangerous in a quarry with a maximum depth of 40 feet.

 

[PR_SMITH]

I'll bite. Who would put pure o2 in a scuba tank? I assume he's writing of a full sized 80.

Lots of tech divers carry a scuba tank of 100% o2

 

[broncobowsher]

I'll bite. Who would put pure o2 in a scuba tank? I assume he's writing of a full sized 80.

Have them as well. Marked as such. Also filled with 70 or 80%, which is nearly the same as 100%.

 

[steinbil]

Do you analyze Every Single Tank you dive, even when diving "air"?

Yes, I do.

Takes very little time and effort. Cheap insurance against human error. To be fair I almost always dive nitrox, but I analyze every tank. I could see the argument for not analyzing a tank from a place that only fills compressed air, but it's so quick and easy to analyze...

 

[John C. Ratliff]

Don’t dive it if you’re not nitrox certified.

I’m sorry, but from a physiological point of view, that sounds off base. Just what trouble, what’s behind your recommendation?

Now, for all you who are talking about analyzing the oxygen content of tanks of air (not nitrox), and saying that they also need to be analyzed, I think you’re missing something. What they need to analyzed for is not really oxygen, as air is 21% oxygen, no blending or membrane work, just air. But the real hazard is not the oxygen content, but the potential for carbon monoxide being sucked into the tank (analyze for CO). How many of you tech divers analyze for CO?

SeaRat

 

[ReefHound]

I’m sorry, but from a physiological point of view, that sounds off base. Just what trouble, what’s behind your recommendation?

Now, for all you who are talking about analyzing the oxygen content of tanks of air (not nitrox), and saying that they also need to be analyzed, I think you’re missing something. What they need to analyzed for is not really oxygen, as air is 21% oxygen, no blending or membrane work, just air. But the real hazard is not the oxygen content, but the potential for carbon monoxide being sucked into the tank (analyze for CO). How many of you tech divers analyze for CO?

SeaRat

Contaminants is a whole other issue.

What you're missing is that you don't often know if there was no membrane or blending work - that a tank didn't get in the wrong area and filled with something other than air by a new tank monkey. All those saying "my shop can only fill air" are all experienced veterans. Most divers don't know what's behind the curtain at their dive shop or what they can or cannot do. And most divers at a dive resort have no idea how air magically gets in their tanks every day.

There are places like Cozumel where one company (Meridiano 87) fills most of the tanks on the island. Most dive ops don't have their own compressors. Tanks are lined up on the curb in the afternoon, a truck picks them up, Meridiano fills overnight (air and nitrox) in a warehouse with a couple dozen fill whips hanging from overhead, and a truck delivers them back to the curb early next morning. Not even your dive op really knows what is in them. Btw, Meridiano also fills most of the tanks on the island for industrial and medical use.

 

[L13]

Contaminants is a whole other issue.

What you're missing is that you don't often know if there was no membrane or blending work - that a tank didn't get in the wrong area and filled with something other than air by a new tank monkey. All those saying "my shop can only fill air" are all experienced veterans. Most divers don't know what's behind the curtain at their dive shop or what they can or cannot do. And most divers at a dive resort have no idea how air magically gets in their tanks every day.

There are places like Cozumel where one company (Meridiano 87) fills most of the tanks on the island. Most dive ops don't have their own compressors. Tanks are lined up on the curb in the afternoon, a truck picks them up, Meridiano fills overnight (air and nitrox) in a warehouse with a couple dozen fill whips hanging from overhead, and a truck delivers them back to the curb early next morning. Not even your dive op really knows what is in them. Btw, Meridiano also fills most of the tanks on the island for industrial and medical use.
View attachment 792334

And somehow, all those "Air" divers manage to dive safely with analyzing their tanks themselves. But all the nitrox divers are "unsafe" if they don't.

 

[John C. Ratliff]

Contaminants is a whole other issue.

What you're missing is that you don't often know if there was no membrane or blending work - that a tank didn't get in the wrong area and filled with something other than air by a new tank monkey. All those saying "my shop can only fill air" are all experienced veterans. Most divers don't know what's behind the curtain at their dive shop or what they can or cannot do. And most divers at a dive resort have no idea how air magically gets in their tanks every day.

There are places like Cozumel where one company (Meridiano 87) fills most of the tanks on the island. Most dive ops don't have their own compressors. Tanks are lined up on the curb in the afternoon, a truck picks them up, Meridiano fills overnight (air and nitrox) in a warehouse with a couple dozen fill whips hanging from overhead, and a truck delivers them back to the curb early next morning. Not even your dive op really knows what is in them. Btw, Meridiano also fills most of the tanks on the island for industrial and medical use.
View attachment 792334

ReefHound,

This sounds right for travel divers, but not all of us travel to dive. Some of us (a few, it seems) dive locally with our LDS filling our tanks.

SeaRat

 

[ReefHound]

ReefHound,

This sounds right for travel divers, but not all of us travel to dive. Some of us (a few, it seems) dive locally with our LDS filling our tanks.

SeaRat

That's more than enough to support my position. I was responding to several statements that it's dangerous to not know exactly what is in your tank by showing that many divers do not know. Furthermore, they are not taught to know. No agency is telling "air" divers to analyze their tanks in case they somehow got filled with something other than air. Apparently, it's good enough to trust the dive shops when they say "here, this is an air tank". Then they take a EAN course and are taught to analyze tanks and suddenly the same dive shop cannot be trusted when they say "here, this is a 32% EAN tank".

 

[John C. Ratliff]

That's more than enough to support my position. I was responding to several statements that it's dangerous to not know exactly what is in your tank by showing that many divers do not know. Furthermore, they are not taught to know. No agency is telling "air" divers to analyze their tanks in case they somehow got filled with something other than air. Apparently, it's good enough to trust the dive shops when they say "here, this is an air tank". Then they take a EAN course and are taught to analyze tanks and suddenly the same dive shop cannot be trusted when they say "here, this is a 32% EAN tank".

You know that this is only a “modern” problem. With the advent of nitrox, this can now happen. But in the days of old, no one had nitrox. Now it’s the “in” thing, and these mixups could happen. So I can see analyzing for oxygen content any tank coming from a dive shop that produces both air and nitrox for diving (or sends it out). But some dive shops (mine, for instance) do not offer nitrox.

SeaRat