2008 NEC 513.3(c)(2) Question

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RCollette

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The NEC in 2008 added the classification requirements for paint hangars to the code which provides some relaxation of having to classify the whole hangar as a paint booth. While the section does a great job of defining the limits of the classifications in the hangar bay it is not clear on how this would extend to communicating spaces. There will be mixed thoughts on whether a door constitutes "suitably cut-off" but for the sake of argument lets assume that it does not (direct discussion with NFPA on this topic determined that their position is a door does not count since it could be propped open and there are no physical controls to make sure it is closed... topic for a different discussion). With the new criteria for paint hangar limits what would be reasonable to anticipate for the hazardous envelopes outside of door openings? If we follow the paint booth scenarios of yesteryear then we have the 3 foot Class I Div 2 bubbles extending outwards from any of the booth openings... what do we do here now? Do we look at the limits applied by 513.3(C)(2) and have it extend through all openings or chop it off at the door way and have a three foot bubble? Per 513.3(B), where not suitably cut off, the fuel vapor limits extend outward for an undefined distance (unless you are the Air National Guard with a limit of 25 feet). Does that same logic of progressing past doorways, without a three foot limit, apply to 513.3(c)(2) also? Conservative approach would be that it would extend outward... but as you can imagine that would impact construction budget and functionality of the communicating spaces. Thoughts?
 
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