Method Exit bag and inert gas megathread

[jiaaa_02]

Hi all, I've been following this thread for a while now and am contemplating a couple of methodologies based on equipment available to me. At the moment, I have the following:

1. 2x 220L nitrogen tanks with regulator and flow meter that goes up to 12lpm
2. Plastic drawstring bag (thick, good size for my head)
3. Duct tape
4. Oximeter
5. Equipment for a CO method, including gas stoves, briquettes, CO gauge

I understand that you typically need 600L to allow for flexibility as well as a flow rate of 15lpm, but I was only able to procure the above in my locale. Would it be a recipe for failure if I set up two nitrogen tanks at 10-12pm each? I want to be careful about accidentally blowing up the bag due to too much flow. I also plan to directly have the hose close to my nose so that my first breath inside the bag is simply nitrogen.

I would appreciate any critiques of the method so that I can get this foolproof.

On a side note, what would be the logistical downside of coupling both the CO and nitrogen methods? I presume CO in the room around me would help induce hypoxia and if one doesn't cause ctb, the other will.

 

[devils~advocate]

I wonder if a high flow nasal cannula with a mouth guard (that is made to circumvent mouth breathing) would work with a hood?
The high flow cannula is made for up to 60 lpm. A regular nasal cannula can do 4-6 lpm.
Normal breathing is about 0.5L per breath at a rate of 12-20 times per minute, which is about 6-10 lpm.

 

[limeoctave]

I wonder if a high flow nasal cannula with a mouth guard (that is made to circumvent mouth breathing) would work with a hood?
The high flow cannula is made for up to 60 lpm. A regular nasal cannula can do 4-6 lpm.
Normal breathing is about 0.5L per breath at a rate of 12-20 times per minute, which is about 6-10 lpm.
View attachment 142377

can you describe in more detail how it should work?

 

[Kapsyl]

I wonder if a high flow nasal cannula with a mouth guard (that is made to circumvent mouth breathing) would work with a hood?
The high flow cannula is made for up to 60 lpm. A regular nasal cannula can do 4-6 lpm.
Normal breathing is about 0.5L per breath at a rate of 12-20 times per minute, which is about 6-10 lpm.
View attachment 142377

How would it benefit from using the regular inner mask of the hood? Or are you referring to the exit bag?

I can tell from experience from using a closed constant flow setup that 10/lpm is not nearly enough, even with shallow breath 25/lpm was just enough to feel comfortable 30-35/lpm is what I'm going to use most likely.

 

[devils~advocate]

Yes, with a exit bag setup I suppose. Just trying to be efficient with the gas usage and point of discharge.
With the cannula it could be delivered straight to the point of intake.
There are high flow nasal cannula that can deliver up to 60 lpm. Then the idea is to limit the ability to mouth breath with a mouth guard device that would inhibit that from happening...rebreathing CO2. (They are used for people who tend to sleep and breath thru their mouths.)

The mouth device may be a non-issue, since exhaust breath would also have inert gas as well.
Just thinking about ideas for those that plan on an exit bag or hood with constant flow system.

I think though the limiting factor is the regulator for the gas flow. The flow meters on them tend to top out at about 60 scfh which is about 30 l/m.
I guess the other limiting factor is the size of the inert gas tank. It has to be big enough to deliver 20-30 l/m for 15-20 minutes.

 

[Kapsyl]

Yes, with a exit bag setup I suppose. Just trying to be efficient with the gas usage and point of discharge.
With the cannula it could be delivered straight to the point of intake.
There are high flow nasal cannula that can deliver up to 60 lpm. Then the idea is to limit the ability to mouth breath with a mouth guard device that would inhibit that from happening...rebreathing CO2. (They are used for people who tend to sleep and breath thru their mouths.)

The mouth device may be a non-issue, since exhaust breath would also have inert gas as well.
Just thinking about ideas for those that plan on an exit bag or hood with constant flow system.

I think though the limiting factor is the regulator for the gas flow. The flow meters on them tend to top out at about 60 scfh which is about 30 l/m.
I guess the other limiting factor is the size of the inert gas tank. It has to be big enough to deliver 20-30 l/m for 15-20 minutes.

Interesting idea, since nitrogen is roughly the same density as ordinary air it makes sense to direct the nitrogen into the respiratory system more efficiently. I would recommend a dual setup, one with the cannula and one ordinary for the bag. I'm worried with only using the cannula the bag will stick into your face because of vacuum and I'm not convinced that the elastic with a hose will sufficiently stop air entering the bag.

I'm not sure about the mount piece, you have to exhale so limiting to nasal exhale could be problematic if you simultaneously push nitrogen into it. I believe you would still breathing co2 for a while since it's stored in the blood, it would take longer than 1-2 to replace all the co2 in the system.

I recommend around 1000 liters anyway so you have enough to practice, even at 30/lpm is enough for 30 mins.

I'm glad you trying to come up with alternatives, the inert method hasn't really changed much since Eebd hood and I believe there are still alternatives to explore. Mask setups (not scba scuba) has been frowned upon and I'm trying to change that opinion.

 

[suffering_mo]

For those in the US, I called a couple of places about the nitrogen. I can rent the tank, which is good because I don't plan to stick around. However, I'm getting the run around when I ask for the info on the purest nitrogen they have. For the nationwide company that begins with Air, they said they have different types. That the best is "Industrial" grade. However, when I asked about the purity, the guy said he's asked before and no one has ever been able to answer that question.

The other smaller company also wouldn't tell me. They just said, tell me what you need it for and I can tell you what kind to get. Ugh.

Anyone in the US know what "Grade" to get from the Air___ Company?

 

[devils~advocate]

Interesting idea, since nitrogen is roughly the same density as ordinary air it makes sense to direct the nitrogen into the respiratory system more efficiently. I would recommend a dual setup, one with the cannula and one ordinary for the bag. I'm worried with only using the cannula the bag will stick into your face because of vacuum and I'm not convinced that the elastic with a hose will sufficiently stop air entering the bag.

I'm not sure about the mount piece, you have to exhale so limiting to nasal exhale could be problematic if you simultaneously push nitrogen into it. I believe you would still breathing co2 for a while since it's stored in the blood, it would take longer than 1-2 to replace all the co2 in the system.

I recommend around 1000 liters anyway so you have enough to practice, even at 30/lpm is enough for 30 mins.

I'm glad you trying to come up with alternatives, the inert method hasn't really changed much since Eebd hood and I believe there are still alternatives to explore. Mask setups (not scba scuba) has been frowned upon and I'm trying to change that opinion.

I agree, the mouth device is more than likely a non-issue and not worth the effort.
A constant flow system seems to be straight forward and the less complex than a scba setup.
(My personal system setup is scba, the exact same like gas monkey describes in their thread.)

Do you happen to have photos of the EEBD hood system you are talking about? Any data on flow, volume. etc. Its good to know any technical data.
For instance, before this forum, I didnt know the recommended flow for inert gas was 15 l/m. Now, it seems 30 l/m is a good flow to use.

Yes, just trying to come up with ideas. Some people have asked about regulators, tanks, etc....how to obtain, if certain ones will work, etc.
I hope to put together a visual guide that shows all this rather than just text descriptions for both the scba & hood system.

 

[Kapsyl]

I agree, the mouth device is more than likely a non-issue and not worth the effort.
A constant flow system seems to be straight forward and the less complex than a scba setup.
(My personal system setup is scba, the exact same like gas monkey describes in their thread.)

Do you happen to have photos of the EEBD hood system you are talking about? Any data on flow, volume. etc. Its good to know any technical data.
For instance, before this forum, I didnt know the recommended flow for inert gas was 15 l/m. Now, it seems 30 l/m is a good flow to use.

Yes, just trying to come up with ideas. Some people have asked about regulators, tanks, etc....how to obtain, if certain ones will work, etc.
I hope to put together a visual guide that shows all this rather than just text descriptions for both the scba & hood system.

Well I'm not using a Eebd hood, Im using a gas mask modified to breath from a reservoir connected to nitrogen.

Gas mask with reservoir, inert gas

I'm looking for advice for a variation of the inert gas method but using a military grade gas mask which is connected to a nitrogen filled environment instead. I haven’t seen this variation of inert gas proposed so I figured it was worthy its own thread I propose using this gas mask...

sanctioned-suicide.net

I've never actually held an eebd hood, I don't think they're completely airtight since most can use it with 25-30/lpm. My system is completely airtight and I struggle if the flow is too low.

The inert method has become more expensive since the absence of accessible helium which made this method good and affordable. More alternatives using nitrogen should be available since I've read some having difficulties with exit bag and nitrogen.

 

[devils~advocate]

For those in the US, I called a couple of places about the nitrogen. I can rent the tank, which is good because I don't plan to stick around. However, I'm getting the run around when I ask for the info on the purest nitrogen they have. For the nationwide company that begins with Air, they said they have different types. That the best is "Industrial" grade. However, when I asked about the purity, the guy said he's asked before and no one has ever been able to answer that question.

The other smaller company also wouldn't tell me. They just said, tell me what you need it for and I can tell you what kind to get. Ugh.

Anyone in the US know what "Grade" to get from the Air___ Company?

I thought most nitrogen was offered at least to 99%.
Grades include, Industrial, Food Grade, Medical, Ultra High Purity, etc, etc.
My thoughts are that they are all typically around 99% and the grades are about impurities and if they have been tested to industry standards. So an Food Grade might be the same as the Industrial, but its been tested officially by some standard testing.
Also it seems that nitrogen classifications include N2.0, N3.0, N4.0, N5.0, N6.0, and N7.0. And these grades get into how pure it goes beyond 99%. (number of 9's beyond)
(I might be off about all this)

I guess one can always tell the retail that you are using it for ....electronic/computer testing systems etc...something they wouldnt know anything about.
That you just need at least 99% purity and that it doesnt matter what grade it happens to be. Its in their benefit to sell you the more expensive gas anyway.

If you contact them again, let us know what you find out.

Well I'm not using a Eebd hood, Im using a gas mask modified to breath from a reservoir connected to nitrogen.

Gas mask with reservoir, inert gas

I'm looking for advice for a variation of the inert gas method but using a military grade gas mask which is connected to a nitrogen filled environment instead. I haven’t seen this variation of inert gas proposed so I figured it was worthy its own thread I propose using this gas mask...

sanctioned-suicide.net

I've never actually held an eebd hood, I don't think they're completely airtight since most can use it with 25-30/lpm. My system is completely airtight and I struggle if the flow is too low.

The inert method has become more expensive since the absence of accessible helium which made this method good and affordable. More alternatives using nitrogen should be available since I've read some having difficulties with exit bag and nitrogen.

I'll have to read the thread about your system.
What problems have you had with an exit bag & nitrogen?

 

[suffering_mo]

I thought most nitrogen was offered at least to 99%.
Grades include, Industrial, Food Grade, Medical, Ultra High Purity, etc, etc.
My thoughts are that they are all typically around 99% and the grades are about impurities and if they have been tested to industry standards. So an Food Grade might be the same as the Industrial, but its been tested officially by some standard testing.
Also it seems that nitrogen classifications include N2.0, N3.0, N4.0, N5.0, N6.0, and N7.0. And these grades get into how pure it goes beyond 99%. (number of 9's beyond)
(I might be off about all this)

I guess one can always tell the retail that you are using it for ....electronic/computer testing systems etc...something they wouldnt know anything about.
That you just need at least 99% purity and that it doesnt matter what grade it happens to be. Its in their benefit to sell you the more expensive gas anyway.

If you contact them again, let us know what you find out.

I'll have to read the thread about your system.
What problems have you had with an exit bag & nitrogen?

So searching online, I found purity info for 95% and above. I found out you can rent the tanks for .70 a day or like $125/yr.

 

[suffering_mo]

So I'm trying to see if I can find a smaller mask because the companies don't carry them in stock. This one, I found on E site. It is an SCBA...I'm wondering if it would work but it looks like there are air holes. Is this an issue? I don't know much about these masks. I will cross post on the SCBA page.

 

[devils~advocate]

View attachment 142405
So I'm trying to see if I can find a smaller mask because the companies don't carry them in stock. This one, I found on E site. It is an SCBA...I'm wondering if it would work but it looks like there are air holes. Is this an issue? I don't know much about these masks. I will cross post on the SCBA page.

This is a SCBA mask used with a Lung demand valve (LDV). It goes into the big holed opening at the mouth part of the mask.
The LVD is attached by a hose to the scba regulator, which in turn is connected to the tank.
(I dont have all my photos with me, that show the various parts. See the post by Gas Monkey)

All these parts can be obtained at various places, including where you found this mask.
I think its good to keep the same manufacturer for all the parts to work together properly.
Im not sure if different manufacturers can be used interchangeably.

 

[suffering_mo]

This is a SCBA mask used with a Lung demand valve (LDV). It goes into the big holed opening at the mouth part of the mask.
The LVD is attached by a hose to the scba regulator, which in turn is connected to the tank.
(I dont have all my photos with me, that show the various parts. See the post by Gas Monkey)

All these parts can be obtained at various places, including where you found this mask.
I think its good to keep the same manufacturer for all the parts to work together properly.
Im not sure if different manufacturers can be used interchangeably.

Yes, it would be the same manufacturer as the regulator. I wonder why it's only half the price of the other masks. I guess I would need to just research and make sure it's compatible.

 

[devils~advocate]

Yes, it would be the same manufacturer as the regulator. I wonder why it's only half the price of the other masks. I guess I would need to just research and make sure it's compatible

Not sure why one mask would be cheaper than another. Seems they would all be similar in price.
Yes, I'd say try to keep the parts compatible.

There are five parts to this type of scba system:

1) inert gas tank (nitrogen, helium, etc) Nitrogen tanks have a female threaded connection valve. It is the type cga-580. Pressure of gas is about 2200 psi
(Helium tanks seems to use the same cga-580 connection) Background info: Gas tanks have a variety connections based on what types of gas they hold...its so that someone can't unintentionally connect one to something its not supposed to connect to.

2) connection adapter: The tanks connection is cga-580. The scba regulator mentioned below can't connect directly to this. The scba regulator has a different type of cga connection...usually a cga-346 or 347 female connection. The 346 is the older low pressure type (2216 psi) and the 347 is the high pressure type (4000 psi). They both have the same threads, except the 347 is slightly longer.
There are adapters to connect from cga-580 to cga-346 (or 347). Usually they are brass. It just screws into the tanks connection 580 and the other end has the threads for the 346. Currently there is just the 580 to 346 connector. But there is a way to connect to a 347 with a different adapter.

3) scba regulator: It might be called by something else than this. But it essentially reduces the pressure from the tank down to what the mask can use (100 ps)
It doesnt have an adjustable valve on it like conventional regulators for industrial use...its made to reduce it to a set amount so the user (fire fighter) doesnt have to adjust knobs etc. As mentioned above, there are different connection types cga-346/ or 347, both will work.

4) lung demand valve (LDV): This device is connected by a hose to the regulator. Its basically a one way valve that works on breath demand. When the user breaths in, it allows air flow thru. When the user breaths out, it stops. There is usually a large red button on it that sets the ldv valve to work.

5) mask: The ldv fits into the mask at a port, usually it snaps in. The mask has one way valves that allow exhaust breath to escape.

 

[suffering_mo]

Thanks. That's helpful.bI don't know regarding the mask. I wanted to ask rigbone because he chose the more expensive one....

The cheaper one is

1)Dräger FPS® 7000 RA-EPDM-S1-PC-EPDM(this one has a fan looking piece in the mouth piece area) - almost half the price

Versus

2)Dräger FPS 7000 P EPDM Mask - PN (this one does not) I am inserting photos of both.

#1


#2

 

[outrider567]

For those in the US, I called a couple of places about the nitrogen. I can rent the tank, which is good because I don't plan to stick around. However, I'm getting the run around when I ask for the info on the purest nitrogen they have. For the nationwide company that begins with Air, they said they have different types. That the best is "Industrial" grade. However, when I asked about the purity, the guy said he's asked before and no one has ever been able to answer that question.

The other smaller company also wouldn't tell me. They just said, tell me what you need it for and I can tell you what kind to get. Ugh.

Anyone in the US know what "Grade" to get from the Air___ Company?

The companies I talked to said by law they can't sell Nitrogen below 99.0%, which is a perfectly acceptable Nitrogen percentage to CTB with

 

[devils~advocate]

Thanks. That's helpful.bI don't know regarding the mask. I wanted to ask rigbone because he chose the more expensive one....

The cheaper one is

1)Dräger FPS® 7000 RA-EPDM-S1-PC-EPDM(this one has a fan looking piece in the mouth piece area) - almost half the price

Versus

2)Dräger FPS 7000 P EPDM Mask - PN (this one does not) I am inserting photos of both.

#1
View attachment 142431

#2

View attachment 142429I

I think the options for the masks, are with the front port. Some are more for European areas.
Its how the lung demand valve fits in to that port.
If you do purchase the mask, make sure you get a the ldv to match the port.
If in the US, im not sure one can get anything other than the kind that available to the US market. I think this is the P type.

RA - thread connection Rd40
PE - thread connection M45x3
ESA - plug in connection (DIN 58600)
P - plug in connection
RP - plug in connection (closed circuit)

#1 photo is the RA version. If you zoom in, you can see threads in that large port area. This is where a threaded kind of ldv or a an air powered system would screw in. RA models seem to be associated with PAPR (powered air purifying respirator)


Most of the ldv's that I have seen available are the P plug in type. These just plug into the port.
There is a little release button on the mask that allow you to pop the ldv out.

The #2 mask, P type, doesnt have the threads in the port. Its made so this P plug ldv can pop in & out.
I think it has to do with fire fighters making it easier to operate & put together in the midst of smoke etc.

 

[suffering_mo]

@devils~advocate Very, very helpful!! This makes a lot of sense.

 

[devils~advocate]

@devils~advocate Very, very helpful!! This makes a lot of sense.

Unfortunately, there is a lot of variation in that industry & products. Not only with the different types, but it seems they change every so often due to the standards they have to go by change. The gov't is strict about standards & they revise them sometimes. The manufacturers have to abide by them.
But for the most part, the US market is fairly stable & change doesnt happen so much. I think it has to do with finances of the agencies (fire depts, etc) that use this equipment. They aren't going to purchase tens of thousands $$ every few years just bc the manufacturers upgrade to a totally different way of putting it together.

Case in point:
If one decides to get an air tank that is made for scba, in order to practice & test things out...there are some restrictions one should be aware of.
In order to get one of these tanks filled legally, the tank has to be manufactured within 15 years & it has to have a testing stamp (hydrostatic test) within 5 years.
This is some US gov't rule for all tanks being used for breathing.
This is why some of the tanks offered for sale online are so cheap....they are out of date. So be aware while searching...make sure the manuf date is within 15 yrs.
You can get the tank tested locally for the hydrostatic test...they do it all the time for fire depts etc. The ones I know of are the fire equipment businesses. If not, they can direct you to ones that can do it.
The place that will fill the tanks (scuba dive shops, etc) with air will be looking for the manuf date & the testing stamp. They want to make sure the tank is good to go before they take the risk of filling it to a high pressure.

I sent you a private conversation message that goes into detail about the other parts & for an adapter for the cga-347 type.
If it makes sense, I can post here for everyone to see.

 

[suffering_mo]

This is very informative. I'm glad you mentioned this.....I don't think I have the time/ability/$ to get an oxygen tank for practice. Would it even be necessary if all parts are new from the manufacturer? I sent you a PM.

 

[devils~advocate]

This is very informative. I'm glad you mentioned this.....I don't think I have the time/ability/$ to get an oxygen tank for practice. Would it even be necessary if all parts are new from the manufacturer? I sent you a PM.

Brand new, it should work great. I guess for me the air tank is for practice....getting used to the system...how it works...etc

I guess one way to think about it....the system works fine...one won't really know in the end. ; )

 

[suffering_mo]

Wanted to put this out there for US folks....I have called a lot of gas places. Industrial nitrogen ranges from 90 to 99% in variation and you won't know what you are getting unless you test it. Food grade nitrogen comes in a different cylinder that is not CGA 580 compliant. For UHP nitrogen, which is 99.9% pure, almost all places only have those in 300 cu ft cylinders. This includes the national gas company that starts with Air. I only found ONE place in my area after calling that can give me an UHP option in an 80 cu ft tank and I have to call back and confirm that it's a CGA 580 tank. This is proving to be very concerning for this method and it would explain a lot of failures for regular people thinking they can just pick up the 40 cu ft tank, use an exit bag, etc. @Tears in Rain doesn't the nitrogen have to be about 97% or higher for CTB?

 

[suffering_mo]

I think I found a tank...a needle in a haystack. However, can you experts explain to me....is there risk of "suffocating" feeling, once you start breathing in the nitrogen and you no longer have oxygen? If you use a SCBA system? Or any other system? Also, how loud is the release of the nitrogen? Is there a hissing sound that could be overheard if you are in a hotel? @Tears in Rain @outrider567 @kudaphillips @Kapsyl

 

[outrider567]

I think I found a tank...a needle in a haystack. However, can you experts explain to me....is there risk of "suffocating" feeling, once you start breathing in the nitrogen and you no longer have oxygen? If you use a SCBA system? Or any other system? Also, how loud is the release of the nitrogen? Is there a hissing sound that could be overheard if you are in a hotel? @Tears in Rain @outrider567 @kudaphillips @Kapsyl

There is zero 'suffocating' feeling while breathing Nitrogen, you breathe 78% Nitrogen every day--I've tested mine 6 times, its just like breathing air, and the hissing is minimal, but you can always wear ear plugs like I do--The human body has a design flaw, it doesn't recognize 99% Nitrogen as life-threatening, thus no physical reaction to it, you just go to sleep

 

[devils~advocate]

Outrider567, have you tested the purity of the Nitrogen gas?
There has been some thought that the purity varies greatly.
My thoughts were that it usually is around 99% in most cases. Its just the number of 9s past this where different grades come into play.
Is there a particular grade & tank size one should ask for? I thought regular Industrial would work fine. This is regards to SCBA method.

 

[suffering_mo]

The important variable here is not how big the volume of the tank but rather what pressure is it under. The tank you mentioned is at 100bar, but the one in PP is at 200bar. Twice the pressure and twice of amount of nitrogen.

Always look at the amount of uncompressed gas rather than the size of the tank. I use a 5 liter tank at 200bar which is about 1000 liter of uncompressed nitrogen.

@Kapsyl I have a question about this, especially when you are going to buy a pre-filled tank. If the nitrogen is in a 40 cu ft tank, and that's just how they sell it to you, how do you know how much nitrogen you are getting? How could you possibly know how many "bars" of gas there are?

Also, how do we know how much nitrogen will be needed? If it's an on demand system, like SCBA, I would "guess," that you would need less gas.

Any explanation here about all this would be great.

 

[devils~advocate]

@Kapsyl I have a question about this, especially when you are going to buy a pre-filled tank. If the nitrogen is in a 40 cu ft tank, and that's just how they sell it to you, how do you know how much nitrogen you are getting? How could you possibly know how many "bars" of gas there are?

Also, how do we know how much nitrogen will be needed? If it's an on demand system, like SCBA, I would "guess," that you would need less gas.

Any explanation here about all this would be great.

The cylinder (tank) they sell to you should have the amount per the size.
They are usually color coded or have a sticker on them stating what they contain.
There might be data also labeled on it that states how much it has in it & the pressure it is at. Its all an industry standard.
The cylinders for nitrogen are made to hold it exclusively. You can't interchange gases in cylinders.

So a 40 cubic foot cylinder will have just about that...40 cf, which is about 1100 liters.
It will also be at about 2200 psi or more (pounds per square inch) of pressure in the US. (which is about 150 bar)
(Bars is the metric unit of pressure 100kPa. Used everywhere in the world except the US.)

40 cf is sufficient. It is equivalent to 5L cylinder metric. If they had normal air in them, they would last about 30-40 minutes in a scba system.
Because these are the same size cylinders & pressure that fire fighters use.

 

[Kapsyl]

@Kapsyl I have a question about this, especially when you are going to buy a pre-filled tank. If the nitrogen is in a 40 cu ft tank, and that's just how they sell it to you, how do you know how much nitrogen you are getting? How could you possibly know how many "bars" of gas there are?

Also, how do we know how much nitrogen will be needed? If it's an on demand system, like SCBA, I would "guess," that you would need less gas.

Any explanation here about all this would be great.

Simply! By looking at the pressure gauge, mine had one built in the cylinder. Am I correct that you're doing a scuba setup? What I understand they're also outfitted with a pressure gauge to notify the user how much "air" left in the tank. That would indicate that your cylinder is full.



I'm not sure, but it would make sense that you would use less since nothing is going to waste. I found some specifications for scba air consumption, the reason I'm not looking at scuba is that more air is required while diving because of pressure.

Looks like your cylinder should last you around 55 min or so, plenty of time.

View attachment IMG_1281.webp

 

[suffering_mo]

Simply! By looking at the pressure gauge, mine had one built in the cylinder. Am I correct that you're doing a scuba setup? What I understand they're also outfitted with a pressure gauge to notify the user how much "air" left in the tank. That would indicate that your cylinder is full.

View attachment 142516

I'm not sure, but it would make sense that you would use less since nothing is going to waste. I found some specifications for scba air consumption, the reason I'm not looking at scuba is that more air is required while diving because of pressure.

Looks like your cylinder should last you around 55 min or so, plenty of time.

View attachment 142519

Thank you. I'm considering SCBA... feeling a time crunch but trying to learn all I can to see if it's something I can make work. It's quite expensive unfortunately.