Clarification 2
Clarification 2
You and the NRTL must reread 500.7(K)(3) carefully. The equipment inside the panel must still be suitable for Class I, Division 2. You cannot “de-classify” a location with gas detection alone. In fact, if you understand the basic definition of Division 2 correctly [500.5(B)(2)(1), last clause] then gas detection means the location must be Division 2 as a minimum. Furthermore, once you detect the gas you are instantly in a Division 1 location.
The NRTL is erroneously attempting to apply a purging/pressurizing philosophy [NFPA 496] where the protection technique actually does alter the classification.
(Note: the NRTL stated that the restrictions of such an installation as is being attempted are rigid and not commonly used.)
How does API RP 500 2012 edition 6.5.1 come into play? According to that section. Use of gas detection along with vapor tight construction of the structure or and I quote (Similar Area) can be used to declassify an area.
The engineer of this project and its design which I am questioning with the NRTL and through this form as resources for information, is using (Similar Area) as substantiation to use gas detection equipment inside the 508 industrial control panels to not have to relocate what is by definition equipment in NEC 100 out of the C1 D2 area.
Granted this engineer has stamped and signed the documentation for this design. But it does not mean its right. And I in good conscience am trying to understand the whole thing before power gets connected and the equipment is processing flammable gases. As anybody whos been around the Electrical Industry for any amount of time, the NEC sometimes is GREY as with 500.7(K) which references the API in informational note 2.
Unless this post changes the thinking on my question. Your opinion from previous posts the devices inside the 508 industrial control panels need to be rated for C1 D2 or installed in an Explosion proof enclosure.
Gas detection equipment does NOT even though API RP 500 6.5.1 states you can do it, declassify the inside of the of an area through use of gas detection equipment and vapor tight construction or (similar area).