IECEx and Hazardous Area Zoning

IECEx and Hazardous Area Zoning

IECEx and Hazardous Area Zoning
in Hydrogen Refuelling Stations


Explosion protection

Explosion protection is divided into two areas:

  1. Electrical classification
  2. Mechanical classification

Electrically actuated solenoid valves, of course belong to the electrical classification. When they are used in hydrogen service, a couple of things need to be considered. It’s up to the hydrogen station designer to define the hazardous area zoning. Three different zones are defined:

  1. Zone 2 - hydrogen in the defined protection area is unusual, but it can happen.
  2. Zone 1 - hydrogen needs to be considered occasionally during normal operation
  3. Zone 0 - hydrogen is mostly present in the protection area.

For the above-mentioned zones, different protection classes are available, which makes sure there is no potential source of ignition.

The protection classes are Class ‘A’, ‘B’ and ‘C’. Protection class ‘A’ is the highest rated, followed by ‘B’ and ‘C’.

  • For hazardous areas in Zone 0, all components must be Class ‘A’ protection rated.
  • For hazardous areas in Zone 1, components must have at least, Class ‘B’ protection, but Class ‘A’ is preferable as it is higher rated.
  • For hazardous areas in Zone 2, all protection classes (‘A’, ‘B’ or ‘C’) can be used.

Hydrogen belongs to the fluid group “IIC”, which also includes Acetylene and carbon disulphide.


The next criteria is the maximum permitted surface temperature. The temperature range starts at 85°C (T6 rated) up to 450°C (T1 rated). There are a couple of in-between steps, but for hydrogen the T1 class is sufficient, as hydrogen has a high ignition temperature.

Electric Rating

Overall, the minimum rating for electrified equipment for hydrogen service must include Ex IIC T6 G_.



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