Ex Glossary
Many Hong Kong industrial users have limited Ex knowledge. Here are the most common explosion-proof terms.
- Hazardous Area
- A location where flammable gas, vapour or dust may form an explosive atmosphere, classified by frequency of occurrence.
- Zone 0 / 1 / 2
- Gas/vapour zones: Zone 0 present continuously, Zone 1 likely in normal operation, Zone 2 only briefly under abnormal conditions.
- Zone 20 / 21 / 22
- Dust zones: Zone 20 continuous, Zone 21 likely in normal operation, Zone 22 only briefly under abnormal conditions.
- ATEX
- The EU explosion-protection directive governing Ex equipment on the European market. Required for export to Europe.
- IECEx
- The IEC's globally recognised Ex certification scheme; the international reference commonly used in Hong Kong.
- Ex d (Flameproof)
- Enclosure withstands an internal explosion and prevents flame transmission to the surrounding atmosphere.
- Ex e (Increased Safety)
- No arcs or sparks under normal operation, adding a margin of safety.
- Ex i (Intrinsic Safety)
- Limits circuit energy so it cannot ignite the explosive atmosphere; common for instrument loops.
- Ex n (Non-sparking)
- Does not ignite the atmosphere in normal operation; mainly for Zone 2.
- Temperature Class (T1–T6)
- Maximum surface temperature rating, which must stay below the ignition temperature of the flammable material. T6 is strictest (≤85°C).
- IP Rating
- Ingress protection level of an enclosure against solids and liquids, e.g. IP65, IP66.
- CoC (Certificate of Conformity)
- Ex certification document; IECEx numbers can be verified on the iecex.com database.