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 Post subject: Layering FR rated clothing
PostPosted: Thu Feb 24, 2011 8:56 pm 
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If you wear a 12cal/cm2 coverall over a 5cal/cm2 coverall are you now protected to 17cal/cm2? Or if you are wearing a pair of 8cal coveralls over denim jeans and a long sleeve denim shirt does this protect you to a level greater than 8cal? Is there a formula for figuring this out?


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PostPosted: Fri Feb 25, 2011 6:37 am 
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Read NFPA70E-2009 Annex M, Section M.1.1

Layering is allowed.


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PostPosted: Fri Feb 25, 2011 6:52 am 
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geh7752 wrote:
Read NFPA70E-2009 Annex M, Section M.1.1

Layering is allowed.

But needs to be tested.
Quote:
M.3.1 It is important to understand that the total system arc rating cannot be determined by adding the arc ratings of the individual layers....The only way to determine the total system arc rating is to conduct a multilayer arc test...


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PostPosted: Fri Feb 25, 2011 7:17 am 
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Read NFPA70E Article 130(12)(a) it specifically mentions "layering system"....

Annex M is not part of the NFPA requirements. If you read the entire M.3.1 paragragh, it said in a "few cases" (no specific numbers or documented facts) the FR was decreased by layering. M.3.1 is a disclaimer statement. I would be very interested in reading study data where layering was actually tested. Anyone?


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PostPosted: Fri Feb 25, 2011 12:40 pm 
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And don't forget HRC.
Two plus two equals 3, brilliant. :eek:


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PostPosted: Tue Mar 01, 2011 10:19 am 
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M.1.1 has some interesting arithmetic in the third sentence. Seems they added the 8 from the pants to the 8 from the shirt to the 25 from the suit to get 40 (rounded from 41 I guess). I would add the 8 only one time.


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PostPosted: Tue Mar 01, 2011 3:13 pm 
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stevenal wrote:
M.1.1 has some interesting arithmetic in the third sentence. Seems they added the 8 from the pants to the 8 from the shirt to the 25 from the suit to get 40 (rounded from 41 I guess). I would add the 8 only one time.

That is not what it says.
M.1.1 says "suit over (pants and shirt)". There is no mention of adding the individual component's values.

In fact, M.3.1 specifically says the combination must be tested.


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PostPosted: Tue Mar 01, 2011 4:28 pm 
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Layering typically does increase the arc rating of the garment system, however the actual garment/fabric combination must be arc tested in order to determine the actual arc rating. Some fabric manufacturers have tested various combinations of their fabrics to establish a layered arc rating and many of these rating are available when requested of either the fabric or garment manufacturers.


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PostPosted: Tue Mar 01, 2011 5:47 pm 
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JBD wrote:
That is not what it says.
M.1.1 says "suit over (pants and shirt)". There is no mention of adding the individual component's values.

In fact, M.3.1 specifically says the combination must be tested.



So how did they get 40 given 25 and 8 and 8? No mention of testing in M.1.1. Looks like addition to me, with a bit of rounding.


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PostPosted: Tue Mar 01, 2011 7:43 pm 
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stevenal wrote:
So how did they get 40 given 25 and 8 and 8? No mention of testing in M.1.1. Looks like addition to me, with a bit of rounding.


M.1.1 simply gives an example of how layering can be effective, not how to determine the effect.


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PostPosted: Wed Mar 02, 2011 9:48 am 
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layering of FR clothing

geh7752 wrote:
Read NFPA70E Article 130(12)(a) it specifically mentions "layering system"....

Annex M is not part of the NFPA requirements. If you read the entire M.3.1 paragragh, it said in a "few cases" (no specific numbers or documented facts) the FR was decreased by layering. M.3.1 is a disclaimer statement. I would be very interested in reading study data where layering was actually tested. Anyone?


Another FPN that is NOT part of the standard is:
"The arc rating for a particular clothing system can be obtained from the FR clothing manufacturer"
:confused:


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PostPosted: Wed Mar 02, 2011 10:27 am 
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To layer or not to layer... that is the question. :confused:

NFPA70E Article 130(12)(a) specifically mentions "layering system". Annex M is not a NFPA requirement but doesn't say annex M can't be used as reference for layering.

Check out Article 130(12)....

"Personal protective equipment items will normally be used in conjunction with one another as a system to provide the appropriate level of protection."

My interpretation is layering is acceptable as long as the combined ATPV meets or exceed the minimum cal/cm^ requirements of the task.

Can this get any more confusing??


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PostPosted: Wed Mar 02, 2011 10:39 am 
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stevenal wrote:
So how did they get 40 given 25 and 8 and 8? No mention of testing in M.1.1. Looks like addition to me, with a bit of rounding.


Don't you get a additional rating factor with the layering system because of the trapped air space between the layers?


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PostPosted: Wed Mar 02, 2011 10:56 am 
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cbauer wrote:
Don't you get a additional rating factor with the layering system because of the trapped air space between the layers?


For this you definitely need to test the combination. No accepted factor exists.


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PostPosted: Thu Mar 10, 2011 5:52 pm 
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A little trip

to a web site or two will give you the combination ratings. Those numbers just go to prove you need the certification testing. This is NOT simple math.


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