Department of Interior
API RP 500, Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Division 1 and Division 2, Third Edition, December 2012, Global Standards
U. S. Department of Interior.
Source: API RP 49, Recommended Practice for Drilling and Well Servicing Operations Involving Hydrogen Sulfide, Third Edition, May 2001. Global Standards