Electrical Area Classification Calculator

API RP 500/505 & NEC Article 500

Professional Area Classification Calculator
Determines Division 1 and Division 2 (or Zone 1/Zone 2) hazardous area extents based on release source type per API RP 500, API RP 505, and NEC Article 500/505.

Classification System

Release Source

Ventilation

Operating Pressure

psig

Higher pressure may increase classified area extent for some sources.

Division vs Zone System

Division System (US Traditional):
  • Division 1: Normal operation hazard
  • Division 2: Abnormal conditions only
Zone System (IEC-based):
  • Zone 0: Continuous hazard
  • Zone 1: Normal operation hazard
  • Zone 2: Abnormal conditions only

Limitations

  • Extents are based on API RP 500 Figure recommendations - site-specific analysis may differ
  • Does not account for heavier-than-air accumulation in pits or below-grade areas
  • Consult qualified electrical engineer for final area classification drawings

Standards & References

  • API RP 500
    Classification of Locations - Division System
  • API RP 505
    Classification of Locations - Zone System
  • NEC Article 500
    Hazardous Locations - Division
  • NEC Article 505
    Hazardous Locations - Zone

Frequently Asked Questions

What is electrical area classification?

Electrical area classification defines hazardous zones around equipment where flammable gases may be present, determining what type of electrical equipment can be installed.

What standards does this area classification calculator follow?

It calculates Division 1 and Division 2 hazardous area extents per API RP 500, API RP 505, and NEC Article 500.

What is the difference between Division 1 and Division 2?

Division 1 areas have flammable concentrations under normal operations, while Division 2 areas only have flammable concentrations under abnormal or fault conditions.