A piece of equipment that is designated as intrinsically safe has been designed to operate in a potentially explosive environment. In simplest terms, under any operating conditions, the equipment and wiring are not capable of releasing sufficient electrical
or thermal energy for ignition.
What types of environments are potentially explosive? We often think of flammable gasses or fuels, but dust and fine powder can also create potentially explosive environments. Common work environments for which intrinsically safe devices are necessary
include on oil rigs, in refineries, in mining operations, pharmaceutical manufacturing, and chemical factories.
Different areas of the world have different requirements and approvals needed for intrinsically safe products. Be sure to review the specific marking on your equipment to ensure it is suitable for your application.
Manufacturer and User Responsibilities for Intrinsically Safe Devices
As a user of intrinsically safe equipment, it is your responsibility to be familiar with the intrinsic safety marking, refrain from tampering with or attempting to repair the device, and use the device as directed. In turn, manufacturers must manufacture
and repair the device in the manner approved by the certification agency, provide instructions on proper use, properly mark equipment, and clearly represent the equipment's capabilities
For example, when using Larson Davis' Spartan Intrinsically Safe Noise Dosimeter Model 730IS, only the approved item (the dosimeter itself with clips and windscreen) may be used in the hazardous environment. The Acoustic Calibrator CAL150, carrying case,
and wireless charger may not. The Spartan-IS should be charged, set up, and calibrated prior to being taken into the hazardous environment.
USA and Canada
In the USA and Canada, Class indicates the "fuel" present in the environment
- Class 1: Flammable gases vapors and mists
- Class 2: Combustible dusts
- Class 3: Easily ignitable fibers
Div indicates the risk of an explosive atmosphere
- Div 1: Explosive atmosphere present or occasionally present
- Div 2: Explosive atmosphere occurs rarely
Class 1, Div 1 environments require intrinsically safe devices.
ATEX/IECEx (Europe and Worldwide)
In Europe and throughout the rest of the world, Group and Zone designations are used:
- Group I: Mine
- Group II: Gas
- Group III: Dust
Zone indicates the likelihood of an explosive atmosphere:
- Zone 0: Explosive atmosphere present
- Zone 1: Explosive atmosphere likely to occur
- Zone 2: Explosive atmosphere likely to not occur
ATEX/IECEx Instrument Markings Example
ATEX(IECx) and USA/Canada Comparison
| ||ATEX(IEC)||North America|
|Mines||Group I|| |
|Gas||Group II||Class 1|
|Dust||Group III||Class 2|Class 1, Division 1 = Group II, Zone 0
| ||ATEC (IEC) Gas||ATEC (IEC) Dust||North America|
|Explosive atmosphere present||Zone 0||Zone 20||Division 1|
|Explosive atmosphere likely||Zone 1||Zone 21|
|Explosive atmosphere not likely||Zone 2||Zone 22||Division 2|