The ATEX standard - Explosive environments
Under what conditions can an explosion occur?
A risk of explosion becomes possible when several elements are present, examples below:
- Oxidant: Oxygen present in the air
gas vapours: solvents, dilutants, hydrocarbons, varnishes, perfumes, dyes, alcohol, gas, chemical products, etc.
dust and powders: flour, sulfur, carbon, magnesium, aluminium, milk, resins, starch, cellulose, sugar, etc.
a source of combustion or 'hot spot'
For example, when a flour mill is in operation the concentration of dust is very high. A highly dusty atmosphere is very dangerous, a spark or even a rise in temperature could cause an explosion.
When the risk of explosion has been identified in a given environment, a safety requirement relating to equipment will be imposed. The equipment used must be designed to specifically diminish the risk of explosion. For example, ATEX head torches may be required.
The ATEX standard
What is ATEX?
The ATEX European directive requires all heads of organisations to have a full understanding of any risks related to explosive environments. ATEX regulation requires a full explosive evaluation of the company to identify potential explosive environments, measures are then put in place to avoid explosions.
How do you select equipment adapted for explosive environments?
ATEX environments fall within three zones:
- zones 0, 1 or 2 for gases
- zones 20, 21 or 22 for dust
There are two groups of materials:
- Group I: mines and below ground restrictive areas
- Group II: all above ground industries
For Group II industries a category system is in place for equipment associated with each ATEX zone.
|Zone classification ||ATEX classification required for equipment |
(for Group II, above-ground industry)
|Zone 0 (gas) |
Zone 20 (dust)
VERY HIGH LEVEL OF PROTECTION
|The explosive mix is present constantly or for a long period of time |
|Zone 1 (gas) |
Zone 21 (dust)
HIGH LEVEL OF PROTECTION
|An explosive mix may form under normal working conditions |
|Zone 2 (gas) |
Zone 22 (dust)
NORMAL LEVEL OF PROTECTION
|An explosive mix has a small chance of forming and would exist only for a short period |
Specific features of ATEX certified headlamps ATEX head torches classified into different groups often use differing modes of protection against the risk of explosion. The mode of protection will be selected with respect to the zone for which the equipment is intended.
The more restrictive the mode of protection is for a headlamp, the less powerful the lighting will be. The voltage and intensity permitted by the Zone will ensure that the device is unable to produce a spark, arc or dangerous operating temperature.
How are explosive gases classified?
The ATEX standard also classifies explosive gasses against which the user can protect him or herself by using a product that has adapted protection.
For Group II materials, the danger of gases covered by a product grows from subdivision IIA, the least dangerous, to subdivision IIC, the most dangerous.
Example reference gases:
- group I: methane
- group IIA: propane
- group IIB: ethylene
- group IIC: hydrogen/acetylene
To determine gases that may be present and their subdivisions, per type of site, refer to the ranking in subdivision
for gases and vapors relating to group II (surface installation).
Temperature classes of gases and dusts.
Headlamps used in hazardous locations must not produce an external surface temperature great enough to provoke combustion. Differing substances will have varying combustion temperatures, the lower the combustion temperature the higher the risk. Therefore, the equipment to be used in an explosive environment is classified according to the maximal surface temperature it generates.
Ignition and combustion are defined by six temperature classes, T1 to T6. Equipment to be used in a relevant class must always produce a surface temperature substantially lower than the self-ignition temperature of the dust or gases present. View a more comprehensive list of gases and their self-ignition temperatures View a more comprehensive list of dusts and their self-ignition temperatures
ATEX Head torch marking explained
II products which have been designed for use in explosive zones have a specific marking on them. The marking displayed contains all of the information required to determine the correct zones applicable to the item.
Example of marking:
CE 0081 II 2GD Ex nAnL IIB T4
-CE: Equipment meets relevant minimum European standard
-0081: Identification number of the notified body, when it intervenes in the inspection phase of production Here the number corresponds to the LCIE – Bureau Véritas. This number may also be 0080, for example for INERIS.
-: Authorised for use in explosive environments
-II: Equipment group (I = mines, II = surface industries)
-2: Equipment category (1 = permanent risk (zones 0 and 20), 2 = frequent risk (zones 1 and 21), 3 = occasional risk (zones 2 and 22))
-GD: Type of fuel source: D = dust, G = gases and vapours
-Ex: Product meets Cenelec protection standards
-nAnL: protection type
-IIB: Classes of gases or vapours covered by the product
-T4:Temperature class corresponding to a surface temperature