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  1. #1

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    Default Mixed Gas for Firefighters

    Anyone out there using Nitrox in their SCBA's, our department is about to test Nitrox in physical tests to determine if there is any advantage to using an Oxygen enriched mix in our SCBA's.


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    Quote Originally Posted by lifeflightmedic View Post
    Anyone out there using Nitrox in their SCBA's, our department is about to test Nitrox in physical tests to determine if there is any advantage to using an Oxygen enriched mix in our SCBA's.
    Are you serious? Are we talking about a fire department here? The two most common recreational diving nitrox mixes are 32% and 36% oxygen. Technical diving mixtures are in excess of 40% oxygen. The dangers of using an oxygen enriched mixture in a fire should be obvious.

    The OSHA respiratory protection standard, 29 CFR 1910.134 regulates everything we do pertaining to SCBA. It requires that the breathing air must meet the specifications prescribed in the Compressed Gas Association (CGA)G-7.1. CGA G-7.1 specifies the oxygen content in the breathing air:
    19.5 - 23.5% for Grade D and a 20 - 22% range for Grade E. NFPA also references the CGA criteria in NFPA 1500 - “Fire Department Occupational Safety and Health Program” and NFPA 1404 “Standard for Fire Service Respiratory Protection”.

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    I thought about this a while ago, logically its a great idea, more o2 less fatigue you would feel. But then someone said, 'what about enriching the atmosphere with this o2?" Hmmmmmmm

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    Not sure about this idea, as a diver i can understand the logic (after all nitrox allows to extend our bottom time) but when diving there is less stress. Here in Queensland an scba tank will last up to 35/40 mins, very rarely will you wear for that time (outside of training) due to heat stress from the fire, physical effort dragging hoses, etc...
    Despite the obvious dangers of O2 in a fire (see above post), if you could extend you're working time would you want to? with the heat and physical effort i wouldn't expect someone to be inside a working fire for more than 30 mins, irrespective of air left in the cylinder. (they need rehydrating, resting, etc..)

    just my opinion

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    I don't foresee nitrox becoming popular anytime soon. But I do wonder just how much those types of packs would actually increase the oxygen level in the environment. We're talking about half again as much oxygen in the tank? By the time we exhale it, I think it'd be minimal enough that it wouldn't be an issue in a room with any size at all.

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    The body absorbs a percentage of the total oxygen intake per breath.

    Increasing the O2 content is purely going to mean increasing the exhaled amount of O2.

    And that will be regardless of work rate, it is a lung function not an O2 content function.

    Get long life tanks if that is your worry.
    Psychiatrists state 1 in 4 people has a mental illness.
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    What prey tell is the problem with a slightly enriched oxygen breathing air mix in a fire?

    Seriously folks, think this one through. As a college professor used to say, what's the physics of the situation?

    Let's do some math...3' x 7' door = 21 s.f. 2mph breeze = 11,000 ft / hr = 183 ft / min = 3,843 cu. ft. of 21% Oxygen air per minute. Hopefully you have more ventilation then just that door. You might even have situations like PPV fans or blow-torch conditions going on that are pumping in many times more air.

    Anyone still scared about a 45 cu. ft. cylinder @ 33% or whatever on your back? Let's recall what the danger is.

    Oxygen is a fire danger in residences, facilities, and vehicles that have a long term exposure to enriched oxygen. In these situations the enriched mixture has permeated the furnishings providing more oxygen closer the fuels. And there's been a few fires in extreme situations that have very high concentrations -- like the Apollo fire with a 100% oxygen environment in the capsule.

    Oxygen can also be used in situation that combine fuel and flame -- like oxyacetlyne or petrogen torches. Oxygen & Fuel together, lacking an ignition source while those two are within their flammable range, aren't burning.

    Far more oxygen will be introduced the fire environment, including around you, by the door you crawled in through than from the 45 cu. ft. cylinder on your back. You're not going to saturate your bunker gear from the occasional use from an enriched cylinder. Since you're normally not sticking you mask into open flame, even a slightly increased concentration of oxygen at the vents isn't going to have any impact since while you have the oxygen and possible fuel part you don't have the ignition source right there.

    Getting back to the original question, I am absolutely convinced I read a Tri-Data(?) report years ago about the European fire service, and one of the small countries around Germany -- I think the low countries, but may Austria, were using enriched O2 SCBA to reduce firefighter stress. However, even a request to the NFA library has failed to find this reference again. I would be kind of surprised if a positive impact had been demonstrated it wouldn't have been adopted on a more wide-spread basis.

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    Forum Member MemphisE34a's Avatar
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    Quote Originally Posted by BackstepFF View Post
    Are you serious? Are we talking about a fire department here? The two most common recreational diving nitrox mixes are 32% and 36% oxygen. Technical diving mixtures are in excess of 40% oxygen. The dangers of using an oxygen enriched mixture in a fire should be obvious.
    It is stored inside the cylinder. It would be no more dangerous than entering with compressed air.

    Anyway, this same topic took off in another thread. If your interested maybe you can find it.
    RK
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    "Everyone goes home" is the mantra for the pussification of the modern, American fire service.


    Comments made are my own. They do not represent the official position or opinion of the Fire Department or the City for which I am employed. In fact, they are normally exactly the opposite.

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    There is no problem with an enriched oxygen feed, in a closed loop system. The key being a "closed loop."
    But the reason for mixed gas is the prevention of nitrogen narcosis or bends, especially for those doing a little more advanced recreational diving.
    Considering we do 99.999% of our firefighting at atmospheric pressure, I'm sure the bends or nitrogen narcosis is not a concern.
    My posts reflect my views and opinions, not the organization I work for or my IAFF local. Some of which they may not agree. I.A.C.O.J. member
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    Quote Originally Posted by MemphisE34a View Post
    It is stored inside the cylinder. It would be no more dangerous than entering with compressed air.
    Quote Originally Posted by SPFDRum View Post
    There is no problem with an enriched oxygen feed, in a closed loop system. The key being a "closed loop."
    Hmmm... so, in other words, there is no problem until there is a problem. What happens when the facepiece gets compromised or dislodged?

    Quoted straight from the MSDS sheet:
    "Oxygen is a colorless, odorless and tasteless gas. It will support life. It is noncombustible, but will actively support the burning of combustible materials. Some materials that will not burn in air will burn in oxygen. Materials that burn in air will burn more vigorously in oxygen."

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    Quote Originally Posted by BackstepFF View Post
    Hmmm... so, in other words, there is no problem until there is a problem. What happens when the facepiece gets compromised or dislodged?

    Quoted straight from the MSDS sheet:
    "Oxygen is a colorless, odorless and tasteless gas. It will support life. It is noncombustible, but will actively support the burning of combustible materials. Some materials that will not burn in air will burn in oxygen. Materials that burn in air will burn more vigorously in oxygen."
    See Dal's post. The amount of oxygen that escapes is going to be miniscule compared to the volume of the environment.

    It's also not going to be much compared to what we're leaking now. Breathing air is 19.5-23.5% Oxygen, while Nitrox is still only 32-36%. Now, if you rapidly released 100% oxygen in a substantial quantity, I might see an issue. However, releasing even 36% oxygen mix through a mask leak into a room isn't going to be much at all compared to the oxygen you're letting in by venting or opening the door, especially if you put a 5,000cfm PPV fan in the door.

    Are you seeing even the slightest increase in burning with what's leaking out your mask now? Do you really think adding half-again the oxygen is going to cause some kind of flashover or something?

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    Quote Originally Posted by lifeflightmedic View Post
    our department is about to test Nitrox in physical tests
    Your department by itself or in connection with a credible testing agency with appropriate safety controls?

    What do you plan on putting the Nitrox in?

    Who is supplying the Nitrox mix?

    Is the delivery system / mix OSHA approved for fire service use?

    These are questions you should be asking. You can't just decide to fill your SCBA with Nitrox from the local dive shop and use it for firefighting.
    Last edited by DeputyMarshal; 06-12-2007 at 12:44 PM.
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    Forum Member MemphisE34a's Avatar
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    Quote Originally Posted by Catch22 View Post
    The amount of oxygen that escapes is going to be miniscule compared to the volume of the environment.
    Exactly. I slow leak around a face piece will have no bearing on the overall O2 concentration through an entire structure, even the effect of the entire volume of an SCBA bottle inside a structure would be negligible.

    Deputy, you are acting like O2 is a flammable gas. It is not. It only supports combustion. A leaking face piece seal is not going to magically cause fire to appear around your face piece. Unless your face is resting on a burning piece of material, I very seriously doubt that any leak would make any noticeable difference in the intensity of the fire. Even if it did, have someone with water put it out.

    Because I know your going to bring it up, what about a catastrophic SCBA failure - okay, that may intensify the fire for a second, but the wearer will have much more to worry about at that point - besides - name one instance where that has ever happened under fire conditions.
    RK
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    Management is making sure things are done right. Leadership is doing the right thing. The fire service needs alot more leaders and a lot less managers.

    "Everyone goes home" is the mantra for the pussification of the modern, American fire service.


    Comments made are my own. They do not represent the official position or opinion of the Fire Department or the City for which I am employed. In fact, they are normally exactly the opposite.

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    Forum Member MemphisE34a's Avatar
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    Quote Originally Posted by DeputyMarshal View Post
    These are questions you should be asking. You can't just decide to fill your SCBA with Nitrox from the local dive shop and use it for firefighting.
    I bet they could.
    RK
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    Management is making sure things are done right. Leadership is doing the right thing. The fire service needs alot more leaders and a lot less managers.

    "Everyone goes home" is the mantra for the pussification of the modern, American fire service.


    Comments made are my own. They do not represent the official position or opinion of the Fire Department or the City for which I am employed. In fact, they are normally exactly the opposite.

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    Forum Member DeputyMarshal's Avatar
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    Quote Originally Posted by MemphisE34a View Post
    Deputy, you are acting like O2 is a flammable gas. It is not. It only supports combustion. A leaking face piece seal is not going to magically cause fire to appear around your face piece.
    Excuse me? You seem to be addressing that reply to the wrong poster.
    "Nemo Plus Voluptatis Quam Nos Habant"

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    Forum Member DeputyMarshal's Avatar
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    Quote Originally Posted by MemphisE34a View Post
    I bet they could.
    The fact that it's physically possible doesn't make it legal nor even a good idea.
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

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    I feel the need to address a percieved misconception regarding the enriched Oxygen content of an SCBA and the enriching the O2 content of the atmosphere of the fire room. I dont think this is a concern. However, the atmosphere inside the mask will be of an enriched oxygen concentration and since we are using a positive pressure system here in the US (for the most part anyway) any leaks to the outside will have an enriched O2 Content. Oxygen had the ability to lower the ignition temperature of materials, I wouldnt worry about the saturation of our gear so much as the possiblity of the leak point being more susceptible to combustion.
    I work for an industrial gas supplier, we have specific rules to comply with when working with oxygen and enriched oxygen gases. For my employer anything over 23.5% oxygen is enriched. In 100% oxygen Stainless steel will burn. While we are nowhere near that concentration, I would imagine the rubber face seal around your mask would be susceptible to burning in an enriched environment. Why take the chance. We are already trashing gear by going in too far. Lets not add the possiblity of an O2 fed fire to the mix.
    Shawn M. Cecula
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    IACOJ Division of Fire and EMS

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    Default Let's clear up the misconceptions about nitrox

    First of all, the purpose of Nitrox is not to have oxygen enriched breathing air while SCUBA diving - the purpose is to have LESS nitrogen. Nitrogen enters the blood stream naturally when breathing air, the greater the atmospheric pressure, the more nitrogen enters the bloodstream since it is compressed within your body and in the tank at depth under water. When a diver ascends, the lower resulting pressure will allow the nitrogen in your blood to actually begin to bubble - this is called the bends. Lowering the nitrogen content in the air a diver is breathing allows them to stay down longer since they end up with lower concentrations of nitrogen in the bloodstream; not because they are breathing oxygen enriched air.
    Nitrox was conceived to lower nitrogen, not increase oxygen. I feel it would be a waste of time and VERY expensive to refill cylinders - do some homework and I believe you'll see this is not a good idea.
    Gord

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    Forum Member MemphisE34a's Avatar
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    Quote Originally Posted by DeputyMarshal View Post
    Excuse me? You seem to be addressing that reply to the wrong poster.
    Ah yes, I stand corrected. I had Backstep in my head but must have been looking at your avatar. Apologies.

    Also let me stress that at not time did I ever agree that this would ne a great idea or the solution to getting so damn tired while working at fires.

    I am just saying that I do not think that slightly bumping up the O2 concentration inside air bottles would be nearly as detrimental as some people are trying to imply.
    Last edited by MemphisE34a; 06-12-2007 at 01:53 PM.
    RK
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    Management is making sure things are done right. Leadership is doing the right thing. The fire service needs alot more leaders and a lot less managers.

    "Everyone goes home" is the mantra for the pussification of the modern, American fire service.


    Comments made are my own. They do not represent the official position or opinion of the Fire Department or the City for which I am employed. In fact, they are normally exactly the opposite.

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    So, in summary, most seem to be in agreement that it's 1. illegal, 2. inappropriate, 3. hazardous, with the only argument being the degree of the hazard. That makes it a bad idea in my humble book.
    Maybe Lifeflightmedic's department should be concerned with working out a little more; increase the VO2 max not the concentration of O2 in the SCBA.

    Memphis: Go back and look at the red bold text in my post. I didn't say it was a flammable gas, either.
    Last edited by BackstepFF; 06-12-2007 at 02:54 PM.

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