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An explosion protection mark is a designation used to describe the explosion protection rating, temperature group, explosion protection type, and the areas in which an explosion-proof electrical device can be used. They can be classified into explosion-proof type d, intrinsically safe type i, enhanced safety type e, oil-immersed type o, sand-filled type q, cast-sealed type m, type n, special type s, dust explosion-proof type, etc. In accordance with the requirements of GB 3836 standard, the explosion-proof marking for explosion-proof electrical equipment includes: explosion-proof type + equipment category + (gas group) + temperature group + equipment protection level. 1. Based on the explosion-proof measures adopted, explosion-proof electrical equipment can be classified into flameproof type, increased safety type, intrinsically safe type, positive pressure type, oil-immersed type, sand-filled type, encapsulated type, type n, special type, dust explosion-proof type, etc. Their identifiers are shown in Table 1. https://p3-tt.byteimg.com/origin/pgc-image/eedc4b28fb8e45d3a06898491feeca24?from=pc 2. Equipment categories: Electrical equipment for explosive gas environments are classified as follows: Class I: Electrical equipment for use in coal mines ； Category II: Electrical equipment for other explosive gas environments other than coal mines. Type II explosion-proof electrical equipment is further divided into categories IIA, IIB, and IIC. Electrical equipment for use in environments with flammable dusts is classified into three categories: IIIA, IIIB, and IIIC. 3. The propagation ability of explosive gas mixtures indicates the level of their explosive hazard; the greater the propagation ability of such mixtures, the higher their danger level. The detonation propagation capability of an explosive mixture can be expressed by the maximum test safety gap. At the same time, the ease with which explosive gases, liquid vapors, and mists can be ignited also indicates the level of their explosion risk, which is expressed as a minimum ignition current ratio. Type II flameproof electrical equipment or intrinsically safe electrical equipment is further classified into categories IIA, IIB, and IIC, according to their maximum test safety gap or minimum ignition current ratio applicable to explosive gas mixtures. As shown in Table 2. https://p6-tt.byteimg.com/origin/pgc-image/98fa65dc5ab04a8594456d85c44b749c?from=pc 4. The ignition temperature of an explosive gas mixture in a certain temperature range is the maximum temperature at which it can be ignited. Electrical equipment is classified into groups T1 to T6 based on its maximum surface temperature, such that the maximum surface temperature of electrical equipment in each corresponding group T1 to T6 shall not exceed the allowable value for that temperature group. The relationship between temperature groups, equipment surface temperature, and the ignition temperature of flammable gases or vapors is shown in Table 3. https://p1-tt.byteimg.com/origin/pgc-image/1be0de94dfbd4f918c97b9d071decd60?from=pc 5. Equipment protection level: Coal mine gas environment (Class I). EPL Ma: Equipment installed in explosive environments in coal mines has a \"very high\" level of protection; this level provides sufficient safety to ensure that the equipment will not become a source of ignition, whether it is operating normally, in the event of expected failures or rare faults, or even when there is a sudden presence of gas while the equipment remains powered on. The EPL Mb is a device installed in explosive environments such as coal mines, and it features a \"high\" protection level. This level provides sufficient safety to ensure that the device cannot become a source of ignition under normal operating conditions or in the event of unexpected failures that occur between the sudden appearance of gases and a power outage. Gas (Class II) EPL Ga – Equipment for explosive gas environments, with a \"very high\" protection level; it does not act as a source of ignition under normal operation, or in the event of expected or rare failures. EPL Gb is equipment for explosive gas environments, featuring a \"high\" protection level, and does not constitute a source of ignition under normal operating conditions or in the event of expected failures. EPL Gc are devices for use in explosive gas environments, featuring a \"general\" level of protection; they do not constitute a source of ignition under normal operation, and additional protective measures can also be taken to ensure that no effective source of ignition is created in situations where ignition is likely to occur frequently (such as in the event of a lamp failure). Dust (Class III) EPL Da – Equipment for explosive dust environments, with a \"very high\" protection level; it does not constitute a spark source under normal operation or in the event of expected or rare failures. EPL Db is equipment designed for explosive dust environments, featuring a \"high\" protection level; it does not constitute a source of ignition under normal operation or in the event of expected failures. EPL Db is equipment designed for use in explosive dust environments, featuring a \"normal\" level of protection. It does not constitute a source of ignition during normal operation, and additional protective measures can be taken to ensure that no effective ignition occurs in situations where sources of ignition are likely to appear frequently (such as lamp failures). https://p1-tt.byteimg.com/origin/pgc-image/1fa3e2ab80ed4942bc0c0ce382b9c89c?from=pc