I have a storm water application for which I am not finding a clear definition in regards to the area classification. NFPA 820 defines a "storm sewer" as a "pipe or conduit that carries storm water and surface water, surface water...". A Storm Sewer is classified as a Class 1, Division 2 area. What is the classification of the open air wet well that the storm sewer empties in to? Does the wet well carry the same classification? I would assume so but does the open air allow for the area to be de-rated? Or would I need to confirm a minimum of 12 air changes per hour to de-rate the area?
Can someone point me to the code that definitively addresses this item?