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Thread: SCBA Question

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    Default SCBA Question

    Ok here I am at work and this mornings kitchen table conerversation is about scba. We use scott 4.5. What is the atmospheric pressure within the mask a positive pressure scba. Nobody knows how much more pressure is in the mask as oposed to normal atmospheric pressure of 14.7 psi Please help
    I HAVE NO AMBITION INTHIS WORLD BUT ONE, AND THAT IS TO BE A FIREMAN. THE POSITION MAY, IN THE EYES OF SOME, APPEAR TO BE A LOWLY ONE; BUT THOSE WHO KNOW THE WORK WHICH A FIREMAN DOES HAS TO DO BELIEVE HIS IS A NOBEL CALLING.


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    I cannot give you a definate answer and I am far from a physicist, but it would seem to me it would not need to be much above atmospheric pressure to work as intended. Think about positive pressure ventilation. With all the leaks and seal issues with pressurizing a house, you cannot be raising the pressure inside THAT much above atmosphere and it still works. But now you have me curious too!

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    Our procedures which are very detailed and discuss the different pressures at which stages etc. States that the pressure in the regulator is "slightly above atmospheric pressure". Sorry it isn't an exact number...but I take that to mean very close to atmospheric as it doens't take much to take a breath in.

    FTM-PTB

    PS- I assume by "Mask" you were refering to the facepiece and not the entire assembly. There are different pressures depending on which hose you are refering to and at if you are before or after the PRA.
    Last edited by FFFRED; 09-23-2005 at 12:31 PM.

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    The Scott Spec. for the Static Pressure - ie. no flow, is between .8 to 1.5 inches of water pressure. An inch of water pressure is about 1/27th of a psi.

    Hope this helps.

    Patrick

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    Default math help

    ok the answer I got from scott is:The pressure in the facepiece is measured in inches of H2O. The pressure in the mask at no flow is .8 to 1.5 inches H2O. Each inch of H2O is equal to 1/28th of 1 psi. During flow the pressure ranges from .3 inches to 3.5 inches of H2O.

    Ok thats great but my math is not so what do these numbers equal in PSI?
    I HAVE NO AMBITION INTHIS WORLD BUT ONE, AND THAT IS TO BE A FIREMAN. THE POSITION MAY, IN THE EYES OF SOME, APPEAR TO BE A LOWLY ONE; BUT THOSE WHO KNOW THE WORK WHICH A FIREMAN DOES HAS TO DO BELIEVE HIS IS A NOBEL CALLING.

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    .3 in. H2O = .011 psi
    .8 in. H2O = .029 psi
    1.5 in. H2O = .054 psi
    3.5 in. H2O = .125 psi

    Birken

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    Quote Originally Posted by BirkenVogt
    .3 in. H2O = .011 psi
    .8 in. H2O = .029 psi
    1.5 in. H2O = .054 psi
    3.5 in. H2O = .125 psi

    Birken
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    As an average of 14.7 equalling 1 atmosphere, the PP system of the scott puts outs anywhere between 1.3 and 1.5 atmospheres.

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