| Protection Symbol | Zone 0 | Zone 1 | Zone 2 | Description | Drawing |
| d | • | • | Type of protection in which the parts which can ignite an explosive atmosphere are placed in an enclosure which can withstand the pressure developed during an internal explosion of an explosive mixture and which prevents the transmission of the explosion to the explosive atmosphere surrounding the enclosure. |  | |
| e | • | • | Type of protection in which measures are applied so as to prevent with a higher degree of safety, the possibility of excessive temperatures and of the occurrence of arcs or sparks in the interior and on the external parts of the electrical apparatus, which does not produce them in normal service |  | |
| ia | • | • | • | Type of protection when no spark or any thermal effect in the circuit, produced in the test conditions prescribed in the standards ( which include normal opertaion and specific fault conditions), is capable of causing ignition. |  |
| ib | • | • | “ | “ | |
| ic | • | “ | “ | ||
| ma | • | • | • | Type of protection in which the parts which can ignite an explosive atmosphere are enclosed in a resin sufficiently resitant to the environmental influences in such a way that this explosive atmosphere cannot be ignited by either sparking or heating which may occur within the encapsulation. |  |
| mb | • | • | “ | “ | |
| mc | • | “ | “ | ||
| n | • | Method of protection for electrical equipment designed so that it will not ignite the surrounding explosive atmosphere in normal opertaion and under certain fault conditions specified in the standrds. There are 4 catagories of equipment: nA (non sparking), nC (enclosed break), nR (restricted breathing), nL (limited energy) |  | ||
| o | • | • | Type of protection in which the electrical apparatus is immersed in oil. |  | |
| p | • | • | Type of protection in which the protective inert gas inside the enclosure is maintained at higher pressure than that of the surrounding atmosphere. |  | |
| q | • | • | Type of protection in which the eclosure is filled with a material in a finely granulated state. |  |
Type of protections for dust
| Protection Symbol | Zone 0 | Zone 1 | Zone 2 | Description | Drawing |
| tD | • | • | Electrical apparatus protected by enclosure and surface temperature limitation for use in areas where combustible dust may be present in quantities which could lead to a fire or explosion hazard. The ingnition protection is based on the limitations of the maximum surface temperature of the enclosure and other surfaces which may come into contact with dust and on the restrition of dust ingress into the enclosure by the use of “dust-tight” or “dust-protected” enclosures. This standard is not applicable to electrical apparatus intended for use in underground parts of mines as well as those parts of surface installtions of such mines endangered by firedamp and/or combustible dust; nor does it take account of any risk due to an emission of flammable or toxic gas from the dust. |  | |
| maD | • | • | • | Electrical apparatus protected by encapsulation type of the protection ‘mD’ and surface temperature limitation for use in areas where combustible dust may be present in quantities which could lead to a fire or explosion hazard. Type of protection in which the parts which can ignite an explosive atmosphere are enclosed in resin sufficiently resistant to environmental influences in such a way that a dust cloud or layer cannot be ignited during installation or operation. |  |
| mbD | • | • | “ | “ | |
| iD | • | • | • | Intrinsically safe apparatus intended for use in the potentially explosive dust cloud or dust layer environments and for associated apparatus that is intended for connection to intrinsically safe circuits which enter such environments. Applicable to electrical apparatus in which the electrical circuit themselves are incapable of causing an explosion in the surrounding combustible dust environment |  |