Next exhibit
Apparatus Groups
Devices which are intended for use in potentially explosive atmospheres are divided into two groups. Cf: IEC Standard 60079-0:20
- Group I: Electrical operating facilities for mine workings susceptible to firedamp
- Group II: Electrical operating facilities for use in all other potentially explosive areas with the exception of mine workings susceptible to firedamp
Group II is divided into sub-groups IIA, IIB and IIC. The letter indicates the maximum experimental safe gap (maximum width of the gap on a flashback arrester through which ignition cannot be transmitted). This depends on the explosive material. The degree of danger increases from A to C.
IIA |
| IIB |
| IIC |
sub-group IIA for example covers diesel, petrol, ethane, methane and carbon monoxide. | town gas, hydrogen sulphide and ethylene for example belong in sub-group IIB. | sub-group IIC includes hydrogen, acetylene and carbon disulphide. |
- Group III stands for electrical operating facilities for potentially explosive dust atmospheres.
IIIA |
| IIIB |
| IIIC |
combustible suspended particles | non-conductive dust | conductive dust |
