4)    intrinsic safety (intrinsically safe electric circuit)  "i"  -  type of protection based on restriction of electrical energy (power) of electrical discharge and temperature of the components of electrical equipment  to a level below that which can cause ignition by either sparking or heating effects ;
5)    encapsulation “m” - type of protection whereby parts that are capable of igniting an explosive atmosphere by either sparking or heating are enclosed in a compound in such a way that the explosive atmosphere cannot be ignited under operating or installation conditions;
6)    type of protection "n"  - type of protection applied to electrical apparatus such that, in normal operation and in certain specified (abnormal) conditions, it is not capable of igniting a surrounding explosive gas atmosphere;
7)    oil immersion "о" - type of protection in which the equipment or parts of the equipment are immersed in a protective liquid in such a way that an explosive gas atmosphere which may be above the liquid or outside the enclosure cannot be ignited;
8)    pressurization "р" – type of protection for guarding against the ingress of the external atmosphere into an enclosure or room by maintaining a protective gas therein at a pressure above that of the external atmosphere;
9)    powder filling "q" – type of protection in which the parts capable of igniting an explosive atmosphere are fixed in position and completely surrounded by filling material to prevent ignition of an external explosive atmosphere;
10)                 special protection “s” – type of protection based on the measures of protection other than those specified in items1-9 of the present clause, but which are considered to be sufficient to ensure explosion safety during assessment or tests;
11)                 constructional safety "с" – type of ignition protection in which constructional measures are applied so as to protect against the possibility of ignition from hot surfaces, sparks and adiabatic compression generated by moving parts;
12)   protection by control of ignition source 'b' – type of explosion protection by means of installation in non-electrical equipment of a device, which prevents creation of ignition source and whereby integral sensors detect impending operation and initiate operation of automatic protective and signal devices.
13)   liquid immersion 'k' - a type of protection in which potential ignition sources are made ineffective or separated from the explosive atmosphere by either totally immersing them in a protective liquid, or by partially immersing and continuously coating their active surfaces with a protective liquid in such a way that an explosive atmosphere which may be above the liquid, or outside the equipment enclosure cannot be ignited.
14)   Protection by flow restricting enclosure "fr"   -  type of ignition protection which, by means of an enclosure, reduces the probability of ingress of a surrounding explosive atmosphere into the enclosure to an acceptably low level so that the concentration inside the enclosure is below the lower explosive limit.