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 Post subject: Hearing Protection and NFPA 70E
PostPosted: Mon Jun 29, 2009 8:40 am 
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Location: Scottsdale, Arizona
Just stirring things up (again)
In the 2004 Edition of NFPA 70E, hearing protection / ear canal inserts was only required for category 2 and higher.

The PPE Matrix Table 130.7(C)(10) in the 2009 Edition of NFPA 70E now requires hearing protection / ear canal inserts all the way down to category 0 - basically it appears to always be required.

Just curious on what the thoughts are about this. From personal experience, I headed off a potential arc flash years ago because I heard the faint arcing sound of a stuck contact. This was in a tight location - the lower deck of an aircraft carrier so an arc flash would have been devastating. I was able to close the contact back in and stop the event. But.... I WAS able to hear it.

I am imagining the same event except while wearing hearing protection. If I had been wearing hearing protection, perhaps I would NOT have been able to hear the arcing and then..... ...well at least my hearing would not be damaged.

I understand what the thought was behind this revision, I was in the lab last week and had a few good category 0 tests that still sounded like a shot gun going off in the room. Also had a good category 3 test - very loud, just a slightly longer duration hence the higher energy and category. The HRC's are based on incident energy which is based on working distance and clearing time but the inital "boom" can be similar. Sound tends to carry well past the working distance.

Any thoughts on hearing protection vs. limiting the ability to hear a danger signal?

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Jim Phillips, P.E.
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PostPosted: Mon Jun 29, 2009 10:29 am 
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My company provides the following hearing protection for arc flash hazards. It is EAR #370-2000 ARC Plug. It is a double sided ear plug. Insert one side in your ear when ambient noise levels require hearing protection. Insert the other side in your ear when ambient noise levels do not require hearing protection.

This is a quote from their packaging.

"The yellow tip end should be inserted only when ambient noise levels are not hazardous but arc potential is present. This earplug tip (yellow) incorporates a patented technology designed for, tested and used by the US military to allow for clear hearing during non-hazardous noise and instant protection against impulse noises such as electric arc. Noise level reduction increases with sound level for impulsive noise such as electric arc blast above 110 dB. Estimated attenuation ranges from approximately 0 to 22 dB."

Not sure if they perform as advertised or not.


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PostPosted: Mon Jun 29, 2009 11:42 am 
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My main problem with the new rule is that hearing protection is now required with no arc flash thermal protection, such as a face shield, in front. Meltable clothing is prohibited, but low temperature melting point plastics are inserted in ear canals? The consequence could be much worse than that caused by the sonic exposure. I think the committee failed to think this one through.

Even products marketed for arc flash use, such as the one mentioned above, have no requirement to be tested for melting or ignition in arc exposure.


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PostPosted: Tue Jun 30, 2009 9:10 am 
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While I'm sure there is a good intention and a prudent approach this makes ensuring compliance difficult to enforce. We have areas; storerooms, garages, indoor parking areas, where the lighting is still switched at the 277V circuit breaker, SWD rated.

We are working to convince these people to wear non-meltable clothing, and safety glasses to switch these breakers. We are also having a short arc flash awareness to "qualify" them since they will be the one's switching the breakers each morning and night. Hearing protection is also required now, I think those on this forum and others "in the know" understand why, but it takes some knowledge also on the part of those that are limited in what they are qualified to do and is tough to convey sometimes.


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PostPosted: Tue Jun 30, 2009 2:16 pm 
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Hearing and other senses

The point that Jim makes is one of the reasons that some HSE and engineering professionals find it difficult to embrace the NFPA70E principles. For higher category PPE it is not just hearing that is impaired in some way but also smell and perhaps even sight to a lesser extent. I think that this is a most thought provoking thread and one that does not have easy answers I'm afraid.


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