Method Exit bag and inert gas megathread

[ClownWorld2023]

While there's an exhalation valve on it, it's not great.

Out of curiosity, what issue are you having with the valve of that hood? Is it not working at all?

 

[Falling Slowly]

Out of curiosity, what issue are you having with the valve of that hood? Is it not working at all?

When I exhale deeply with the hood on, I feel a small amount of air going out the front of the valve, but some goes into the hood, especially via the two small holes in the inner mask The holes are probably there to let oxygen flow into the hood, I think maybe I should seal off those holes with tape.

Maybe when there's nitrogen flowing in the hood there will be a pressure against the valve and the CO2 might flow out the valve easier. But it's not a high tech exhale valve or anything. I took the valve apart, and it's basically just a circular piece of plastic against a spring. The exhaled air pushes against the plastic, which pushes against the spring, leaving a gap for exhaled air to go out.
I'm hoping if small amounts of CO2 go into the hood it won't make too much of a difference.

 

[ClownWorld2023]

When I exhale deeply with the hood on, I feel a small amount of air going out the front of the valve, but some goes into the hood, especially via the two small holes in the inner mask The holes are probably there to let oxygen flow into the hood, I think maybe I should seal off those holes with tape.

I see.

Your hood is quite expensive though. I assume it should be fine.


I myself haven't had the chance to test my EEBD hood yet, but I will do it later.
My hood came as part of an actual set. It's made in China so I don't know about the quality, but I hope it's good enough.

Right now I'm doing my best to figure out how to connect it without having to modify the hose.

Maybe when there's nitrogen flowing in the hood there will be a pressure against the valve and the CO2 might flow out the valve easier. But it's not a high tech exhale valve or anything. I took the valve apart, and it's basically just a circular piece of plastic against a spring. The exhaled air pushes against the plastic, which pushes against the spring, leaving a gap for exhaled air to go out.
I'm hoping if small amounts of CO2 go into the hood it won't make too much of a difference.

If you happen to have a diving cylinder or compressed gas cylinder (clean air, not contaminated) you could test it I suppose.

If it was still summer in my area I would've tried this myself, but I think it would be suspicious to get a diving gas cylinder refilled, consider almost no one is going to go diving in this weather.

 

[winterparty]

Yes. This is what I was worried about. @Falling Slowly and I have the 3M Scott hood myself which was recommended by gas monkey so I'm thinking about it.

 

[ClownWorld2023]

Yes. This is what I was worried about. @Falling Slowly and I have the 3M Scott hood myself which was recommended by gas monkey so I'm thinking about it.

There were also problems reported with the PSS hood.

Maybe it's not just those hoods, but all EEBD hoods?

I really hope that's not the case though.


Normally these hoods are used with a EEBD set that uses a relatively high flow rate of 35-40 LPM, some going even higher than that.
So it could be that the exhale valve was designed with that in mind.



Anyway, how are you guys testing the hoods?
Can you just wear it without the hose plugged onto anything and breathe in and out without issues?
Won't there be a problem because no air is being actively supplied into the hood?

 

[winterparty]

Keep in mind that @Vizzy killed himself succesfully with a eebd hood.

 

[Falling Slowly]

Anyway, how are you guys testing the hoods?
Can you just wear it without the hose plugged onto anything and breathe in and out without issues?
Won't there be a problem because no air is being actively supplied into the hood?

So far I haven't done any proper test, just breathing in and out a few times to test the exhalation valve, without the hose plugged in .

Keep in mind that @Vizzy killed himself succesfully with a eebd hood.

Yes, the EEBD hood has worked for some people, though the SCBA setup is probably more reliable.

 

[k1w1]

When I exhale deeply with the hood on, I feel a small amount of air going out the front of the valve, but some goes into the hood, especially via the two small holes in the inner mask The holes are probably there to let oxygen flow into the hood, I think maybe I should seal off those holes with tape.

Maybe when there's nitrogen flowing in the hood there will be a pressure against the valve and the CO2 might flow out the valve easier. But it's not a high tech exhale valve or anything. I took the valve apart, and it's basically just a circular piece of plastic against a spring. The exhaled air pushes against the plastic, which pushes against the spring, leaving a gap for exhaled air to go out.
I'm hoping if small amounts of CO2 go into the hood it won't make too much of a difference.

EEBD hoods become flooded with nitrogen at the recommended lpm rate. That nosepeice and valve looks fairly good compared to mine. Any exhaled gas that remains within the hood will be pushed out at the neck fitting, this is why the elasticated fitting is not 'skin-tight'. It is also why a cylinder with 40 mins flow duration is used. It is if you will excuse the pun, an overkill amount of gas, A great deal of over-thinking goes on here, which is fairly predictable under the circumstances. But when one considers that this method started out as an oven bag with a plastic tube taped inside it, these hoods with the exhalation valve are quite a remarkable development.

It's not possible to refund it, that's why I rather not.


I already found a source for the 344 coupler. The problem is it can take up to a month to get it delivered.

If you live in a city with a workplace safety shop, you can head in and try the fittings out yourself. Same with welding/pneumatic supply shops. I have one fairly close to home & those couplers are on the shelf, unboxed, sold seperately. This should put your mind at rest.

 

[ClownWorld2023]

If you live in a city with a workplace safety shop, you can head in and try the fittings out yourself. Same with welding/pneumatic supply shops. I have one fairly close to home & those couplers are on the shelf, unboxed, sold seperately. This should put your mind at rest.

I went with the 95 KS coupler instead.
I understood that only the 344 series would work, because the 341 and 342 series were not compatible length-wise.
That's what customer support told me.

But anyway, I decided to no longer use that hood, because other members had problems with the exhalation valve.

---

I managed to remove the hose from my EEBD set's pressure reducer, but I don't recognize this male connector.

Does anyone know what it is?
Thread diameter seems to be 8-9mm.

I looked up the thread size charts, but I didn't understand them.

 

[winterparty]

This scared me quite a bit. The hood setup is not 100% reliable? Can a hypercapnic alarm occur? Can someone explain further?

 

[ClownWorld2023]

This scared me quite a bit. The hood setup is not 100% reliable? Can a hypercapnic alarm occur? Can someone explain further?

Two members mentioned the PSS hood exhalation valve not letting out air during exhale.

I'm not sure whether there are other hoods with this issue.


I will wear and test my hood tomorrow.

 

[Dmoore3232]

Will all nitrogen tank hoses attach to this eebd hood? Also is there a standard hose for nitrogen tanks?

 

[Falling Slowly]

I went with the 95 KS coupler instead.

---

I managed to remove the hose from my EEBD set's pressure reducer, but I don't recognize this male connector.

Does anyone know what it is?
Thread diameter seems to be 8-9mm.

I looked up the thread size charts, but I didn't understand them.


View attachment 121405

You'll probably have to either cut the connector off, and hook the hose directly to a regulator connection, if the hose is long enough, and fits. (Using a hose clamp).

Or, seeing as you say that you have a Rectus 95 ks coupling, you have the option of getting an extension hose like this, attaching your hose to that, and plugging it directly into the coupling (that Scott 3m hose will fit that coupling).
Or get just the male hose nipple barb thats used on that extension hose, and put it into your hose. Then plug it into the Rectus coupling.

Will all nitrogen tank hoses attach to this eebd hood? Also is there a standard hose for nitrogen tanks?
View attachment 121410

You don't hook up a hood directly to a nitrogen cylinder, you have to control the flow coming from the cylinder, so you need a nitrogen (or argon) regulator.
Cylinder>>regulator>>hood.

These hoods are usually connected to an air cylinder, so there's no standard hose that connects to a nitrogen regulator.
I'm not sure what kind of hood that is in your pic, but you might be better off getting a hood with a hose attached.

 

[k1w1]

With apologies to the longer term members that are still with us, I have posted this before but Im reposting to answer the above concerns : This is mine (yeah yeah....'there are many like it etc') The hood came with a meter of attached hose & a hokey end fitting which was cut off promptly. The regulator is a wee ripper, being a dual stage with built in flow meter. The last image is the hose join that seems to strike fear into many a heart!! These hoses were the same I/D but slightly different O/D; but with a double barb joiner and ear clamps they cramp down very tight. I have tested all joins with soapy water and they effective and sound. Best wishes, now I just have to find a way of esting it without killing myself !!

 

[ztem]

two small holes in the inner mask The holes are probably there to let oxygen flow into the hood, I think maybe I should seal off those holes with tape.

The Drager Saver CF and LALIZAS have those two holes on the inner mask too , If you think those two holes are a flaw in the design of the hood, seal it.

Maybe when there's nitrogen flowing in the hood there will be a pressure against the valve and the CO2 might flow out the valve easier

There is no doubt about it.

But it's not a high tech exhale

That low tech exhalation valve will do the job, you only need an exhalation valve to prevent carbon dioxide from accumulating inside the hood, cessation of breathing occurs in less than 5 minutes, If you think that exhalation valve can't do its job for 5 minutes, you better sue the manufacturer and get some money from them.

though the SCBA setup is probably more reliable.

The use of SCBA equipment is overkill and unnecessary imo, you just need a confined, oxygen-free space, preferably with an exhalation valve, which a hood will give you that, the SCBA is just a fancy way of doing it.

Does anyone know what it is?
Thread diameter seems to be 8-9mm.

I looked up the thread size charts, but I didn't understand them.

I sent you some adapters for that and you need to spend some money and try them, but as I said, it's better to modify the hose.

 

[winterparty]

OK now I'm confused. So the the two holes matter in terms of co2 getting inside the hood? How would you seal them?

I saw a previous post of yours saying you have the Scott ELSA hood, which I also have. While there's an exhalation valve on it, it's not great. There's also 2 small holes in the inner mask(see pic below), which I presume are to let the air go into the hood itself.
Are you worried about too much CO2 getting into the hood and not going out the

I saw a previous post of yours saying you have the Scott ELSA hood, which I also have. While there's an exhalation valve on it, it's not great. There's also 2 small holes in the inner mask(see pic below), which I presume are to let the air go into the hood itself.
Are you worried about too much CO2 getting into the hood and not going out the exhalation valve?

View attachment 121336

 

[Dmoore3232]

You'll probably have to either cut the connector off, and hook the hose directly to a regulator connection, if the hose is long enough, and fits. (Using a hose clamp).

Or, seeing as you say that you have a Rectus 95 ks coupling, you have the option of getting an extension hose like this, attaching your hose to that, and plugging it directly into the coupling (that Scott 3m hose will fit that coupling).
Or get just the male hose nipple barb thats used on that extension hose, and put it into your hose. Then plug it into the Rectus coupling.

You don't hook up a hood directly to a nitrogen cylinder, you have to control the flow coming from the cylinder, so you need a nitrogen (or argon) regulator.
Cylinder>>regulator>>hood.

These hoods are usually connected to an air cylinder, so there's no standard hose that connects to a nitrogen regulator.
I'm not sure what kind of hood that is in your pic, but you might be better off getting a hood with a hose attached.

Damn, I could almost just run a hose under that like an old school exit bag. You need another hose for air to get out though right?

 

[ClownWorld2023]

I tested breathing in/out of the EEBD hood.

The first time I exhaled out I could feel the air being pushed out of the exhale valve.
It's not being pushed out with much force though. It's a bit faint.

The subsequent in/out exhales, no air was being pushed out of the exhale valve.


I repeated the above two times, same result.


That makes me think it depends on the volume of air that's left inside the hood.



Will repeat it again later for placebo reasons.


EDIT: This was done while standing. Will also repeat it while lying down later.

 

[ClownWorld2023]

Just tested it again two times, now lying down.

First time, exhaled air left both the exhale valve and the collar area (felt it with my hands).

Second time, exhaled air only left the exhale valve (did not feel anything around the collar area).





I tested it like this:

Take EEBD hood. expand the inside with your hands so it gets filled with air, similar to how you would expand the inside of a plastic bag.

Start stretching the collar area of the hood to allow for easy equipping.

Fully breathe in as much air as you can and hold breath.
(Belly breathing)

Equip the hood. Try not to let much air escape while doing this. So keep the collar stretched until your head is inside.
Put on the inner mask on your face and make sure the collar is properly sealed.

Fully exhale with all force.




Note: After the first time you exhale, this no longer works, because too much air has left the EEBD hood.
So to test it again, repeat above steps in the exact same manner.


I tried to explain it as best as I could above.

 

[Falling Slowly]

If you think those two holes are a flaw in the design of the hood, seal it.

Not a flaw; like I said it's probably designed to let air flow into the hood itself. These hoods are designed to keep people alive to get out of an emergency situation; some CO2 mixing in with the air over a few minutes isn't going to affect them staying alive.

But for our purposes, where as close to 100% nitrogen as possible is preferable, it's understandable if people are wondering how effective an exhalation valve is, or whether CO2 will be pushed out the bottom of the hood by the nitrogen, etc.

But like you said, it'll probably work fine when the nitrogen is flowing.

OK now I'm confused. So the the two holes matter in terms of co2 getting inside the hood? How would you seal them?

You probably don't need to seal them with tape or whatever, I was just wondering if it would ensure less CO2 would get into the hood itself, from the mask/mouthpiece.

Damn, I could almost just run a hose under that like an old school exit bag. You need another hose for air to get out though right?

If you're going doing the exit bag setup, you just need the hose from the regulator bringing the gas into the bag. Exhaled air will be pushed out the bottom of the exit bag by the nitrogen.

 

[ClownWorld2023]

Not a flaw; like I said it's probably designed to let air flow into the hood itself. These hoods are designed to keep people alive to get out of an emergency situation; some CO2 mixing in with the air over a few minutes isn't going to affect them staying alive.

But for our purposes, where as close to 100% nitrogen as possible is preferable, it's understandable if people are wondering how effective an exhalation valve is, or whether CO2 will be pushed out the bottom of the hood by the nitrogen, etc.

But like you said, it'll probably work fine when the nitrogen is flowing.

I think it improves the CO2 purging by abit, but it's probably not that significant.
Like, I don't think it's as good as SCBA.


After wearing the EEBD hood, these are the two main advantages I found:

• Proper seal. No need to worry about whether it's too tight or too loose, which also means no ambiguity.
• Durable material. It's much better than a plastic bag.
  You don't need to worry about "ripping off" an EEBD hood because of SI.

In my case, it was difficult to get the hood on. I had to squeeze my head into it, almost choking myself in the process.
The same for taking it off.
It takes quite an effort and a bit of time to remove the hood.

 

[Falling Slowly]

After wearing the EEBD hood, these are the two main advantages I found:

• You don't need to worry about "ripping off" an EEBD hood because of SI.

You've obviously never experienced S.I.!
S.I. may not hinder everyone, and obviously many people overcome it, but for some people, having a tight hood on isn't gonna matter a damn if S.I. overpowers them.

In my case, it was difficult to get the hood on. I had to squeeze my head into it, almost choking myself in the process.
The same for taking it off.
It takes quite an effort and a bit of time to remove the hood.

While your hood seems to be too small for you, if the inner mask sits tightly against your mouth, it may work out better than if it was a bit loose. Is the hood neck not elasticated?

 

[ClownWorld2023]

While your hood seems to be too small for you, if the inner mask sits tightly against your mouth, it may work out better than if it was a bit loose. Is the hood neck not elasticated?

I don't know whether it's elasticated, but it's difficult to get it on and it's quite tight, but after wearing it, the sealing is pretty much perfect.

You've obviously never experienced S.I.!
S.I. may not hinder everyone, and obviously many people overcome it, but for some people, having a tight hood on isn't gonna matter a damn if S.I. overpowers them.

You should strap your dominant hand so you can't use it to "rip off" the EEBD hood.

With a plastic bag I can see it happening, maybe even with one hand, because it's just thin plastic that can readily tear if you want it to.
That just can't happen with an EEBD hood.
I had difficulties taking it off even with two hands.

How are you supposed to take it off if your low on oxygen, (nearing) unconscious and your dominant hand is strapped?

 

[puffnstuff]

I have seen a lot mentioned but can someone post manufactures / models of good EEBD Hoods?

 

[Falling Slowly]

I have seen a lot mentioned but can someone post manufactures / models of good EEBD

People have either gone the cheap route, and bought a hood off the likes of Alibaba. Or bought the likes of Draeger or 3M Scott (e.g. Scott ELSA) hoods. Though some are advising against getting the Draeger PSS hood, due to issues with the exhalation valve. Just try and get one with a hose attached, and an exhalation valve.

 

[winterparty]

What about the the two holes on the inner mask of the 3m scott hood? To seal or not to seal? The picture is there if you scroll upwards.

I saw a previous post of yours saying you have the Scott ELSA hood, which I also have. While there's an exhalation valve on it, it's not great. There's also 2 small holes in the inner mask(see pic below), which I presume are to let the air go into the hood itself.
Are you worried about too much CO2 getting into the hood and not going out the exhalation valve?

View attachment 121336

 

[Falling Slowly]

What about the the two holes on the inner mask of the 3m scott hood? To seal or not to seal? The picture is there if you scroll upwards.

I honestly don't know, it's up to yourself. You are probably better off not sealing the holes, and letting the gas flow into the main hood through those holes. Some CO2 may also go out those holes, but the exhalation valve will probably work better when the gas is flowing.

It may not make too much of a difference if some CO2 gets into the hood. CO2 gets exhaled into an exit bag before it's pushed out the bottom, and that has worked for people. Plus you'll be mostly inhaling through the inner mask once it is snug up against your mouth.

 

[puffnstuff]

People have either gone the cheap route, and bought a hood off the likes of Alibaba. Or bought the likes of Draeger or 3M Scott (e.g. Scott ELSA) hoods. Though some are advising against getting the Draeger PSS hood, due to issues with the exhalation valve. Just try and get one with a hose attached, and an exhalation valve.

What about the EEBD hoods on Alibaba?

 

[ClownWorld2023]

I honestly don't know, it's up to yourself. You are probably better off not sealing the holes, and letting the gas flow into the main hood through those holes. Some CO2 may also go out those holes, but the exhalation valve will probably work better when the gas is flowing.

It should.

The valve should at least work if you test it the same manner as I did above.


Whether the valve will also work at the normal 15-25 LPM flow I don't know.
That's something I'm wondering about too.
I don't have access to breathing air / clean compressed air right now, or I'd test it myself.

 

[RazorWing]

Thank you ztem for your help. I will look at purchasing the side entry regulator you suggested.

There appears to be a few different variations and models of 3M Scott SCBD. There is the Vision 3 and ProMask model each with different variations. Is there any recommend model and variation?

Most of the SCBD masks don't come with the air supply valve so you either need to buy this separately or buy the 3M Scott RAS Positive Pressure Respiratory Airline Apparatus. Is this correct?

Example of 3M Scott RAS

With the RAS, it seems to have enough length to not require an extension hose. For connecting the RAS to the regulator, the RAS uses a male CEN type connector, would this still work with the 3/8 BSP Female to Rectus 95KS Female or would I need a 3/8 BSP Female to a quick release coupling?

3/8 BSP Female to Rectus 95KS Female

3/8 BSP Female to Quick Release Coupling


If a positive pressure demand valve is used like the one with the 3M Scott RAS, could one use a 2L (420L volume) instead or would a larger volume be recommended? The next size up in the UK is 9.4L (1200L volume).