Protection Concepts

There are established engineering concepts recognised by the IEC for the design of electrical equipment for hazardous area applications. These engineering concepts are the basis of protection against the risk of fire or explosion from gas or dust.

Each concept is identified by a protection symbol. If a design relies on more than one concept all symbols are normally shown.

 Gas Protection Concepts
Symbol & EN refConceptSummary Zone useCategory
Ex i EN 60079-11Intrinsic safetyLimits energy of sparks & surface temperatures
0,1 & 21,2 & 3
Ex d EN 60079-1FlameproofContains explosion quenches flame
1 & 22 & 3
Ex e EN 60079-7Increased safetyNo arcs, sparks or hot surfaces
1 & 22 & 3
Ex p EN 60079-2PressurisedKeeps flammable gas out
1 & 22 & 3
Ex m EN 60079-18EncapsulatedKeeps flammable gas out
0,1 & 21,2 & 3
Ex q EN 60079-5Powder filledKeeps flammable gas out
1 & 22 & 3
Ex o EN 60079-6Oil filledKeeps hazard away from ignition source using inert oil
1 & 22 & 3
Ex nA EN 60079-15Non-sparkingNo arcs, sparks or hot surfaces

23
Ex nR EN 60079-15Restricted breathingGasket restricts air movement23
Ex nC EN 60079-15Enclosed breakSealed from air ingress23
Dust Protection Concepts

The explosive nature of dust is generally classified into three groups.

Symbol & EN refConceptZone useCategory
Ex t EN 60079-31Protection by enclosure 20, 21 & 221, 2 & 3
Ex i EN 60079-11
Intrinsic safety20, 21 & 221, 2 & 3
Ex m EN 60079-18Encapsulation20, 21 & 221, 2 & 3
Ex pD EN 61241-4Pressurised21 & 22
2 & 3

Concepts such as Ex i, Ex p, Ex t and Ex m have been split into a, b and c. This allows for a new type of protection called ‘EPL’ or Equipment protection level. For Gas this is Ga, Gb and Gc and for Dust Da, Db and Dc.

According to EN 60079-0 the EPL is the level of protection assigned to equipment based on its likelihood of becoming a source of ignition and distinguishes the differences between explosive gas atmospheres, explosive dust atmospheres and the explosive atmospheres in mines susceptible to firedamp.

Ga and Ma - Very high level of protection

Gb and Mb - High level of protection

Gc and Mc - Enhanced level of protection