本推荐规程提供了确定石油设施中I类、0区、1区和2区位置的等级和范围的指南，用于选择和安装电气设备。本文件的编制遵循了《国家电气规范》中提供的基本定义，适用于临时和永久安装电气设备的位置分类。RP 505适用于在正常大气条件下由于存在可燃气体或与空气混合的蒸汽而可能存在着火风险的情况。

This recommended practice provides guidelines for determining the degree and extent of Class I, Zone 0, Zone 1, and Zone 2 locations at petroleum facilities for the selection and installation of electrical equipment. Basic definitions provided in theNational Electrical Codehave been followed in developing this document, which applies to the classification of locations for both temporarily and permanently installed electrical equipment.RP 505 is intended to be applied where there may be a risk of ignition due to the presence of flammable gas or vapor mixed with air under normal atmospheric conditions.