EI 15 Hazardous Area Classification Review

EI Model code of safe practice – Part 15: Area classification code for installations handling flammable fluids (EI15, formerly referred to as IP15) is a well-established Model Code for area classification in the petroleum industry. It provides a demonstrable methodology for determining hazard radii, applicable to installations handling flammable fluids.


Bluefield were approached to review a previous Hazardous Area Classification for a drilling rig as the Zonal extents seemed excessive.

Areas of concern

  • Zone 2 encompassing the entire rig and extending 15 m laterally outside the rig battery limits
  • Discrepancy on several Zone 0’s.

The original classification was performed using the Energy Institutes “EI Part 15” The preferred classification standard for the UK.

Two possible options for classification methods covered in EI 15

  • The point source approach (calculation)
  • The direct example approach (Method used in original classification)

The direct example approach was used and the client wanted to verify original findings.


The client wanted EI 15 used for the classification review

Bluefield reviewed the standard and the areas of concern to determine accuracy of original classification.

Several solutions were presented to the client to try to reduce the zonal extents.

Apparent excessive Zone 2 areas

  • Have the rig classified to alternate standards
    • By using different standards allows different methods to be utilised to reduce zonal extents
  • Utilise the Point source approach to minimise zones
    • By using calculations would be able to reduce the zonal extents

Apparent excessive Zone 0’s

  • Analyse standards to ensure Zone 0’s kept to a minimum



Alternate standards were not acceptable to the client to keep standardisation consistent for all plant as it had all previously been classified to EI 15

The method utilising calculations was also decided to be unacceptable as this would have taken some time to prepare..

After assessment some zone 0’s were declassified where electrical equipment was not  required to be installed or reduced to a lower zone where electrical

equipment was required  to be installed in the area.

The client was satisfied to know that the original classification was reasonably accurate with addition of the removal of some Zone 0’s.