The categories of equipment intended for work in these types of atmospheres are grouped according to:
1. Group I devices: For work in mines or in outdoor facilities where explosive atmospheres may occur.
- Category M1: Very high protection level.
- Category M2: High protection level
2. Group II devices: Intended for use in other places where there may be a danger of the formation of explosive atmospheres.
- Category 1: Very high level of protection. Even if one means of protection fails, there is another that continues to maintain the level of protection.
- Category 2: High level of protection.
- Category 3: Normal level of protection.
Electrical equipment suitable for explosive areas
Electrical equipment will only be suitable for explosive areas if it is constructed in accordance with one of the following protection modes:
- d = flameproof enclosure. The electrical equipment is enclosed within an enclosure capable of resisting the explosion and not transmitting the ignition to the surrounding environment, neither by its union joints, nor by other communications.
- e = increased security. It is based on ensuring the non-formation of arcs, sparks or overheating in devices, taking: a high safety coefficient, special non-loosening terminals, high quality insulators and with a minimum IP54.
- i = intrinsic safety. An appliance or circuit is intrinsically safe when it is not capable of producing sufficient sparks or thermal effects to ignite a given gas atmosphere. It is indicated for instrumentation, since it consists of designing low voltage circuits and reducing the intensity, also taking into consideration the possible defects that may occur and the energy stores in capacitors, cables and inductances.
- p = internal overpressure. The electrical machines or materials are provided with an enclosure or installed in a room in which the entry of flammable gases or vapors is prevented, keeping air or a non-flammable gas inside, at a pressure higher than the external atmospheric pressure.
- = immersion in oil. It is carried out in such a way that flammable gases or vapors that are above the oil level and outside the enclosure cannot ignite.
- q = powdery insulator. The live parts of the electrical equipment are completely immersed in a mass of powdery insulation.
- m = encapsulated. The elements to be protected are enclosed in a resin, in such a way that an explosive atmosphere cannot be ignited neither by sparks, nor by contact with hot parts inside the encapsulation.