ATEX 95 and the Manufacturer
Under ATEX 95, a manufacturer must evaluate his products and identify them accordingly:
Equipment Groups
The ATEX Directive identifies two groups of equipment:
Equipment Group 1
Equipment in this group is divided into Categories M1 and M2 and is used in mining applications. M1 identifies equipment that must continue to operate when a potentially explosive atmosphere is present. M2 identifies equipment that does not operate when a potentially explosive atmosphere is present.
Equipment Group 2
Equipment in this group is intended for all other applications and is divided into Categories 1, 2 and 3 according to its suitability for use in the different zones as defined in ATEX 137
Equipment Categories
Category 1
Equipment in this category is intended for use in Zone 0 (Gases) and Zone 20 (Dusts) environments and is designed to ensure very high levels of safety. All products within this category have two independent means of safety or are operationally safe in the event of two independent faults occurring.
Category 2
Equipment in this category is intended for use in Zone 1(Gases)/ Zone 21 (Dusts) situations and is designed to ensure a high level of safety. Its explosion protection system must ensure that the required level of safety is maintained even in the event of frequently occurring incidents or equipment malfunctions.
Category 3
Equipment in this category is intended for use in Zone 2 (Gases)/Zone 22 (Dusts) situations and is designed to ensure the requisite level of safety during normal operation.
Zone Classification
An explosive atmosphere is defined as a mixture with air, under atmospheric conditions, of flammable substances in the form of gases, vapours, mists or dusts. Explosive atmospheres are classified into Zoned areas on the basis of the probability of their occurrence.
Zone 0 (Gases)
Zone 20 (Dusts) |
An area in which an explosive atmosphere occurs constantly frequently or for long periods |
Zone 1 (Gases)
Zone 21 (Dusts) |
An area in which an explosive atmosphere occurs occasionally in normal operation |
Zone 2 (Gases)
Zone 22 (Dusts) |
An area in which an explosive atmosphere does not normally occur or occurs only briefly |
Examples of Hazardous Area Zones
Explosion Group
Explosion protected devices are divided into two Explosion Groups.
Group I
Equipment for use in mines. It is assumed that the only flammable gas to occur here is methane. Other flammable gases that can occur in these areas must be further classified as shown with Group II
Group II
Equipment for use in all other hazardous areas. This group is further sub-divided into A, B and C dependent upon the protection method used (intrinsic safety or flameproof enclosure), the minimum ignition current/limit gap and the minimum ignition energy of the gas/vapour.
Temperature Classes
Explosion protected devices are divided into six Temperature Classes based upon ignition temperature. The ignition temperature is the lowest temperature of a surface at which an explosive atmosphere will ignite. The maximum surface temperature must always be lower than the ignition temperature of the gas/air or dust/air mixture.
| T Class |
Max. Surface
Temp °C |
| T6 |
85 |
| T5 |
100 |
| T4 |
135 |
| T3 |
200 |
| T2 |
300 |
| T1 |
450 |
Type of Ignition Protection
Intrinsically safe electrical devices are classified into categories ia and ib. Category ia is suitable for use in Zone 0 and Category ib is for use in Zone 1. All other standardised types of protection should be seen as being equal apart from protection n which can only be used in Zone 2.
| Ia |
Intrinsically Safe (safe with
two faults) |
| Ib |
Intrinsically safe (safe with
one fault) |
| c |
Design safety |
| d |
Flameproof |
| e |
Increased safety |
| p |
Purged and Pressurised |
| m |
Encapsulated |
| o |
Oil filled |
| p |
Powder filled |
| n |
Non-incendive standard |
