Topping off Tri-Mix with air

[Blackwood]

To me it seems like topping up a trimix fill with air is blending trimix. I agree from a practical standpoint a diver could add his O2 and He and go to the local shop to top with air (or add He and go to the shop to top with Nitrox), and he's already done the calculations so the mix will come out correctly. However, I just have to wonder what the shop liability is if the shop-person adding the air isn't certified as a trimix blender. (assuming they were told that they were adding air to trimix). Is it common that shops have employees making mixes (nitrox or trimix) without some formal certification?

I often get air on top of residual nitrox at a shop that doesn't sell nitrox.

 

[Gilldiver]

It's all good. Trust me, I had to look hard and long to find the fills I wanted.

Doesn't Scuba Shack in CT (Scuba Shack) also have a booster? I know they fill air, nitrox, trimix, and argon.

Cape Ann or Cape Cod? I really only ever dived the former (where you had to bring your own nitrox; Atlantic Divers in Danvers was the closest bet otherwise; they *might* have a booster now). For Cape Cod, the only shop I know that pumps nitrox is the Dive Locker in Hyannis (http://capedivelocker.com/). Doubt they have a booster, though.

At lest last year they didn't. They were sending divers to New England Divers for rebreather fills and top offs as they couldn't do 10/90 dilutent fills over bought tank pressures - 2400 psi or so.

I'm thinking Cape Cod, we have to bring a bunch of doubles up there with rich mixes and then get them top off at a shop or one of the Fire Stations.

 

[boulderjohn]

I also still want to know why a MSDT would not know the basics about mixing gas. I can see the new shop monkey with no dives asking about this but an instructor? Even if the shop does not have nitrox, what happens when a student wants a nitrox course? This is all covered. It was in the class I took anyway.

I would be surprised in an area with a lot of local diving, but in other places it is not surprising. Here in Colorado there are not many places at all where you can go and have any real reason to use nitrox, let alone trimix. Almost all of the fills made by most shops are for their own instructors and students to use in the pool and for pretty shallow OW dives. I don't believe the shop with which I worked had ever made their own nitrox until a couple of years ago. Trimix? not even considered. Thus, there was no need for anyone to be a certified blender, and there is a big difference between knowing the basic concepts of blending and actually doing it.

Today we are able to do all that blending, but it is a select group of us who are all certified blenders, and we pretty much do it all for ourselves. We have to travel nearly 7 hours to find a place where it is worth using, but we do it.

That is why there is not much call for it from customers, and why most of the shops in the state don't see a need for it.

 

[SDAnderson]

If the OP was setup to do partial pressure blending, he woudl already be pumping Grade E modified air, wouldn't be asking the question, and it wouldn't be an issue. I'd say "feel free!."

However, since he did ask the question, I'm going to assume he's not setup for partial pressure blending and is not pumping hyperfiltered air.

This means that he may be contaminating the tank, which could become a problem when the tank owner goes to dump in the O2, or even if he isn't contaminating the tank, when the owner burns his house down while filling O2, the first place anybody will look is to the SCUBA shop that filled his tanks with air that wasn't certified to the necessary standards.

You can feel free to fill whatever you please, however from my perspective, it's a ton of liability to accept for a few bucks.

Terry

Yes, you can get sued for anything but, despite the proverb, there definitely is such a thing as being too careful. The guy asks for an air fill, he gets an air fill. So long as he meets the usual standards (hydro, VIP, c-card) no special treatment is necessary or even desirable. I wouldn't make him analyze it, either - he bought an air fill, not a mix fill and requiring him to analyze and log isn't required for air fills. Unless you're going to start analyzing every cylinder before you fill it to make sure it doesn't contain some flavor of voodoo gas...

 

[boulderjohn]

You'd be surprised the number of shops that find anything besides air evil. I know of a shop in Houston that is a Dive Rite dealer that WILL NOT order Dive Rite gear because it is for "tech". Period. They don't do or teach nitrox because it's for "deep diving". In the years I dove BP/W before advanced classes, I bought from any shop besides my local one because they wouldn't sell "tech". And if you wanted a DIN reg, good luck.

I'll bet you could walk into that shop and ask any of their 100 instructors about air topping trimix and get a very similar response. They would then call the owner, who would tell them that they don't do "tech", and the doubles owner would have to find another fill station.

Further, I'll bet 1/2 the LDS's in the United States would have a similar attitude. Any question why the industry is stagnant? I've come to expect the question. I have a couple dive shops in KW that refer ALL their "tech" questions to me, they just don't want to deal with it.

I don't know the shop of which you speak and its motivations, but I am in the middle of a similar situation here in Colorado. There has been a reluctance to go into tech on the part of the LDSs, including the one with which I work, but it is not for the reasons you cite in your message. I know because I have been directly involved with a lot of the thinking and planning in the attempts to offer a tech line.

The first problem is that the tech market is very small. In another recent thread, Phil Ellis, a dealer, said that the information he had was that BP/Ws amounted to only 1% of the BCD sales in America last year. As I just said in another post, the amount of tech diving here is negligible. Go to the Rocky Mountain Oysters site on SB and see my thread about trying to get the state's tech divers to at least identify themselves so that we could possibly do some stuff together.

Given the small market, consider the fact that many of the companies that sell tech gear require a very large minimum original purchase and a very large annual sales commitment. Like the shop you mention, our shop does not sell Dive-Rite. It is not that we have anything against it, it is just that in our market we could not hope to sell anything close to their required minimums. Last year we finally put together enough interest for an initial purchase from Salvo (including a lot of $$$ from me), and now we still have gear to sell from a company that no longer exists.

There is currently great fear that the original group of us who drove the purchases have pretty much spent what we will, and there is not a lot of evidence of new people coming on the scene. It takes a lot of courage for a LDS on the financial edge to make a large monetary commitment to gear it may never sell.

 

[Jim Lapenta]

That is why it is up to the instructors to inform students that so called "tech gear" is not. It is simply a bc that fits better, allows you to fit it to you and in many cases is less expensive than the fancy bc with too many drings, padding you need to add weight to offset, and pockets that are often in the wrong place and hard to get to. The shop I teach at carries halcyon and dive rite. I recommend BPW setups to students who plan to travel. I also recommend long hose and bungee backups. There are 6 instructors from 3 agencies and we all recommend what is best for the students needs, wants, and means. There is one PADI instructor who recommends halcyon to his students. Of course he also has a GUE background. I teach in BPW, jacket bc, and now back inflate(Zeagle express). I put students in jacket bc for half the class and back inflate for half. Let them decide what is best for them. This week I let one use the zeagle after a jacket and back inflate with lots of padding. He will not be buying a regular bc. It'll be a BPW or the Zeagle. If you have salvo gear let the students use it in the pool and see what they think. You may even sell it if they know how it works and actually see the benefits.

 

[Web Monkey]

There is currently great fear that the original group of us who drove the purchases have pretty much spent what we will, and there is not a lot of evidence of new people coming on the scene. It takes a lot of courage for a LDS on the financial edge to make a large monetary commitment to gear it may never sell.

That's completely reasonable from a business perspective.

It's hard enough to sell a good surface float with a dive flag that's required by law. Who wants to stock something that may never sell? You have a 30Lb wing, and the diver wants a 40. You have a 40 horseshoe and he wants an oval. You have a DiveRite and he wants a Halcyon. I certainly wouldn't tie up my money with it.

Terry

 

[Jim Lapenta]

To me it seems like topping up a trimix fill with air is blending trimix. I agree from a practical standpoint a diver could add his O2 and He and go to the local shop to top with air (or add He and go to the shop to top with Nitrox), and he's already done the calculations so the mix will come out correctly. However, I just have to wonder what the shop liability is if the shop-person adding the air isn't certified as a trimix blender. (assuming they were told that they were adding air to trimix). Is it common that shops have employees making mixes (nitrox or trimix) without some formal certification?

All he is doing is adding air. I now know if I ever get back to California and need a mix to call around before expecting to just walk into a supposed full service dive shop and expect them to know what they are doing.