Wetwells are classified as hazardous areas under the definition of NFPA 820. When continuously ventilated at 12 air changes per hour, wastewater pumping station wetwells fall into the category of Class I, Division 2, Group D locations. For electrical installation requirements, see Article V, Electric Service and Distribution, and WSSC 11.120.490, Station lighting. (Design Guideline DG-08 § 5.10, dated August 2006)