In 1991, the American Petroleum Institute (API)
merged their three area classification documents (RP500A
for refineries, RP500B for production and drilling facilities,
and RP500C for transportation/pipeline facilities) into one
document, RP500 [1]. A common general section was
supplemented with three other sections for specific
recommendations for the three sectors of the industry, but,
for all practical purposes, the RP was composed of the three
previous recommended practices bound in a single cover.
In 1997, API created RP505 [2], Classification of Locations
for Electrical Installations at Petroleum Facilities Classified as
Class I, Zone 0, Zone 1, and Zone 2, which will serve the
petroleum industry essentially as an supplement to both ISA
12.24.01 (IEC 79-10 Mod) [3] and National Electrical Code
(NEC) [4] Article 505. RP500, which underwent significant
changes in 1997, is presently referenced by Article 500 of
the NEC; it was proposed that the 1999 NEC would reference
RP505. This paper provides a brief overview of the two new
recommended practices, but primarily emphasizes the
substantive changes and additions to RP500 and the
portions of RP505 with the highest impact on the industry.

API RP 500 2nd Ed. Nov. 1997 w/Aug.1998 Errata (R2002) - Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Division 1 and Division 2 api.pdf 6.939 MB

[link Point to another website Only the registered members can access]
API RP 500 3rd Ed, XXXXX 2008 Ballot Results Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Division 1 and Division 2.pdf 7.281 MB

[link Point to another website Only the registered members can access]
AAPI RP 505 1st Ed. Nov 1997 w/Aug. 1998 Errata - Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Zone 0, Zone 1, and Zone 2.pdf 8.032 MB

[link Point to another website Only the registered members can access]