1. Explosive environment: Generally divided into three categories: Class I-Mine methane environment, Class II-Explosive gas environment, Class III-Explosive dust and fiber environment. 2. Classification of hazardous media: Taking explosive gases as an example, they are divided into three categories: IIA, IIB, and IIC. In contrast, IIA gas is the most difficult to ignite, and IIC gas is the easiest to ignite. 3. Temperature group of explosive medium: Also take explosive gas as an example, divided into 6 groups from T1 to T6. The T1 group gas is the most difficult to ignite, and the T6 group gas is the easiest to ignite. T1: Gas ignition temperature t >450℃ T2: Gas ignition temperature 300< t ≤450℃ T3: Gas ignition temperature 200< t ≤300℃ T4: Gas ignition temperature 135< t ≤200℃ T5: Gas ignition temperature 100< t ≤135℃ T6: Gas ignition temperature 85< t ≤100℃ 4. Division of explosive hazardous areas: Explosive gas environment is divided into zone 0, zone 1, and zone 2. Their corresponding relations are as follows: Zone 0: Under normal circumstances, places where explosive gas mixtures exist continuously or for a long time (above 1000h/year); Zone 1: Under normal circumstances, places where explosive gas mixtures may occur (10~1000h/year); Zone 2: Under normal circumstances, explosive gas mixtures are unlikely to appear (or explosive gas mixtures may only appear under fault conditions), or even if they appear, they only exist for a short time (below 10h/year). 5. Explosion-proof technology: The main electrical explosion-proof technologies currently accepted in China are as follows: Suitable for zone 0: intrinsically safe type Ex ia, glue-sealed type Ex ma Applicable to Zone 1: The explosion-proof type applicable to Zone 0 can be used in Zone 1. In addition, there are intrinsically safe type Ex ib, flameproof type Ex d, Increased safety type Ex e, glue-sealed type Ex mb, positive pressure type Ex px and Ex py, etc. Applicable to Zone 2: The explosion-proof type applicable to Zone 0 and Zone 1 can be used in Zone 2. In addition, there are intrinsically safe Ex ic, glue-sealed Ex mc, positive pressure Ex pz, n-type Ex nA, nC, nR. The explosion-proof level of explosion-proof equipment is defined according to the above five items. 1. Suppose I am a manufacturer and I want to design a motor for a customer. It is required to be suitable for Class II-explosive gas environment, the explosive gas mixture is Class IIC, the gas temperature group is T3, and the motor is installed and used in Zone 1. After research, it was decided to adopt the explosion-proof explosion-proof technology Ex d, and technically meet the requirements of the IIC gas environment. In addition, in order to adapt to the gas group T3, the highest surface temperature of the product should not be higher than 200°C, which is finally verified as 180°C. This leads to another concept, namely the temperature group of explosion-proof electrical equipment, which corresponds to the temperature group of the gas. But it is different from the temperature group of the gas: T1: allowable maximum surface temperature t ≤450℃ T2: allowable maximum surface temperature t ≤300℃ T3: allowable maximum surface temperature t ≤200℃ T4: allowable maximum surface temperature t ≤135℃ T5: allowable maximum surface temperature t ≤100℃ T6: allowable maximum surface temperature t ≤85℃ Therefore, we have determined the explosion-proof level of this motor: Ex d IIC T3 Gb, which means that the equipment can be used in the explosive gas environment of the IIC category T3 temperature group in Zone 1. The explosion-proof type of the equipment is explosion-proof type d, and the equipment protection level EPL is Gb level. 2. If I am a user, I can select the explosion-proof level of the equipment according to the environment in which it is used. And the equipment marked IIB can be applied to the use conditions of IIA equipment, and IIC can be applied to the use conditions of IIA and IIB.