Definition(s)
Normal Atmospheric Conditions
Normal atmospheric conditions are defined as conditions that vary above and below reference levels of 101.3 kPa (14.7 psia) and 200 °C (68 °F) provided that the variations have a negligible effect on the explosion properties of the flammable materials.
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