API RP 500-2023 PDF

Full title and description

API RP 500, Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Division 1 and Division 2 — 4th edition (2023). This recommended practice provides guidance for identifying and classifying hazardous (classified) locations where flammable gases or vapors may be present and for selecting/installing electrical equipment and wiring suitable for Class I, Division 1 and Division 2 environments at petroleum and natural gas facilities.

Abstract

API RP 500 (4th ed., 2023) describes the methodology to determine the location classification (Class I, Division 1 and Division 2) of areas in petroleum facilities where flammable gases or vapors may be present. It aligns definitions with the 2023 edition of NFPA 70 (NEC), adds updated figures and examples, and introduces new material addressing classification at LNG facilities. The RP is intended to guide engineers, inspectors and safety professionals in identifying hazardous areas and selecting appropriate electrical equipment and wiring methods.

General information

• Status: Current (active recommended practice, 4th edition).
• Publication date: June 2023 (4th edition published June 2023 — commonly cited as June 8, 2023).
• Publisher: American Petroleum Institute (API).
• ICS / categories: Electrical installations for explosive atmospheres / explosion protection (commonly mapped to ICS area for electrical apparatus for explosive atmospheres, e.g., 29.260.20).
• Edition / version: 4th edition (2023).
• Number of pages: 183 pages (published copy counts typically shown as 183 pages).

Scope

API RP 500 gives recommended procedures to classify locations at onshore and offshore petroleum facilities where flammable gases or vapors may be present under normal atmospheric conditions and where electrical equipment (temporary or permanent) could present an ignition source. The RP covers criteria for area extent and degree (Division 1 and Division 2), guidance on applying NEC/NFPA definitions, and specific considerations for LNG facilities and common petroleum processes. It is complementary to API RP 505, which addresses the zone-classification system.

Key topics and requirements

• Definitions and classification principles for Class I, Division 1 and Division 2 locations.
• Criteria and procedures to determine extent and degree of hazardous areas based on leak/release sources, ventilation, material properties and process conditions.
• Guidance for selection and installation of electrical equipment and wiring methods suitable for Division-classified locations; coordination with NEC (NFPA 70) requirements.
• New/updated guidance and figures for classification at LNG facilities (refrigeration/liquefaction, storage, loading/unloading areas).
• Examples, diagrams and tables to support area boundary determinations and practical application in field and plant designs.
• Notes on interaction with regulatory requirements (e.g., BSEE references) and complementary standards (API RP 505, NFPA, IEC series).

Typical use and users

Primary users are electrical engineers, process engineers, facility designers, EHS and process safety professionals, inspectors, contractors and regulatory compliance teams working in upstream, midstream and downstream petroleum and LNG facilities. Typical uses include area classification studies, electrical equipment selection and specification, design reviews, inspections and permitting support.

Related standards

Commonly referenced and complementary documents include: API RP 505 (zone system for Class I, Zone 0/1/2); NFPA 70 (NEC); NFPA 497 (classification of flammable liquids/gases/vapors); IEC 60079 series (explosive atmospheres) and applicable national electrical codes and regulations (OSHA, BSEE where referenced). API RP 500 is often used alongside these standards to ensure correct classification and equipment selection.

Keywords

area classification, hazardous locations, Class I Division 1, Class I Division 2, electrical installations, petroleum facilities, LNG classification, NFPA 70, API RP 505, explosion protection

FAQ

Q: What is this standard?

A: API RP 500 is an API recommended practice that provides guidance for classifying hazardous locations (Class I, Division 1 and Division 2) at petroleum facilities and for selecting/installing electrical equipment appropriate to those classifications.

Q: What does it cover?

A: It covers methods to identify sources of flammable releases, determine the extent and degree of classified areas, and select wiring and electrical equipment suitable for Class I, Division 1 and Division 2 locations; it also includes updated material for LNG facility classifications and aligns definitions with NFPA 70.

Q: Who typically uses it?

A: Electrical and process engineers, EHS and process‑safety staff, design contractors, inspectors and regulators involved with petroleum and LNG facilities use this RP for area classification, design, equipment specification and compliance work.

Q: Is it current or superseded?

A: The 4th edition published in 2023 supersedes the 2012 edition (reconfirmed versions). As of the publication of the 4th edition it is the current API RP 500. Users should confirm there has been no later revision or amendment before applying it — the API standards plan and vendor listings show the 2023 (4th) edition as current.

Q: Is it part of a series?

A: Yes — API RP 500 is part of API's suite of electrical area-classification and safety practices and is complementary to API RP 505 (zone-system classification). It also interfaces with NFPA 70 (NEC) and international IEC 60079 series guidance for explosive atmospheres.

Q: What are the key keywords?

A: area classification, hazardous locations, Class I Division 1, Division 2, electrical equipment, petroleum facilities, LNG, NFPA 70, explosion protection.