Construction type for class 1 div. to non classified area

[BJB48]

What type of physical building construction is required to act as delineation between a class 1 div.1 area and a non-classified area. Doing a design review on a small metal building that will be for sewage and scum. Design has a gas fired water heater and air compressor located in a small 7X9' room within the structure. Walls are 3 1/2" steel studs 5/8" gyp board on either side and ceiling with a 4" drywall smoke partition and power ventilation in the room. Engineer has classified the entire building as class 1 div. 1 but we know that can't be right. Is there something in the UBC that would address this? Everything in my past has been cmu or cast concrete. Your help and thoughts would be appreciated.
Thanks
Bruce

 

[rbalex]

The applicable general electrical area classification rule, such as it is, is found in NFPA 497, Section 5.2.2.4:

In cases in which an unpierced barrier, such as a blank wall, completely prevents the spread of the combustible material, the area classification does not extend beyond the barrier.

Note, it makes no distinction about the construction method itself. Technically, a good coat of paint on an otherwise unpierced wallboard is adequate to create a electrical area classification boundary - even for Division 1. Of course, once Classified, the UBC or other appropriate building code needs to be consulted for the actual structural building construction.

There may be other things to consider, such as ventilation and the fact that there is already a constant non-electrical ignition source present (gas fired water heater). It is often an unfortunate consequence of Classified locations that we say we can?t give definite answers without knowing the full details of the installation.

 

[BJB48]

Thanks Bob

Thanks Bob

Bob,
Thanks for your input on my question. Helps a lot.
Rgds.
Bruce