A hazardous area is defined as an area in which an explosive atmosphere is present, or may be expected to be present.

The international standards define three levels of Hazardous Area Classifications: Zone 0, Zone 1 and Zone 2.

Zone 0: An area in which an explosive atmosphere is present continuously, or is present for long periods.

Zone 1: An area in which an explosive atmosphere is likely to occur periodically in normal operation.

Zone 2: An area in which an explosive atmosphere is not likely to occur in normal operation and if it does occur it will exists for a short period only.

Type of Protection for Gas / Vapour

Zone 0, 1 and 2

• Ex ia - Intrinsically Safe
• Ex ma - Encapsulation

Zone 1 and 2

• Ex d - Flameproof
• Ex ib - Intrinsically Safe
• Ex p - Pressurised Enclosure
• Ex pl - Purged Enclosure
• Ex px - Purge / pressurized
• Ex py - Purge / pressurized
• Ex mb - Encapsulation
• Ex e - Increased Safety
• Ex s - Special
• Ex m - Encapsulation
• Ex o - Oil Immersion
• Ex q - Powder / Sand Filled

Zone 2

• Ex n - Non Sparking
• Ex pz - Purge / pressurized
• Ex ic - Intrinsic Safety

Group Classification

• Group I - Coal Mining (methane)
• Group II - Other Industries
• Group IIA (e.g. propane, butane)
• Group IIB (e.g. ethylene, butadiene)
• Group IIC (e.g. acetylene, hydrogen)

Temperature Class

The maximum surface temperature of the equipment should not exceed the ignition temperature of the gas or vapour based on an ambient of 40 °C

• T1 - 450 °C
• T2 - 300 °C
• T3 - 200 °C
• T4 - 135 °C
• T5 - 100 °C
• T6 - 85 °C

   > Ex ia IIC T4
      : Ex - Explosion protected
      : ia - Protection technique applied
      : IIC - Gas group suitability
      : T4 - Maximum surface temperature