How is the flame-retardant and fire-resistant rating of terminal blocks classified? Generally speaking, the flame retardant and fire-resistant rating of wiring terminals increases step by step from HB, V-2, V-1, V-0, 5VB to 5VA, as follows:

　　HB: The lower flame retardant rating in UL94 standard. Require a combustion rate of less than 40 millimeters per minute for samples with a thickness of 3 to 13 millimeters; Samples less than 3 millimeters thick have a combustion rate of less than 70 millimeters per minute; Or extinguish before the 100mm mark.

　　V-2: After two 10 second combustion tests on the sample, the flame extinguishes within 60 seconds. Burning materials may fall off.

　　V-1: After conducting two 10 second combustion tests on the sample, the flame extinguishes within 60 seconds. No combustibles can fall off.

　　V-0: After conducting two 10 second combustion tests on the sample, the flame extinguishes within 30 seconds. No combustibles can fall off.

　　5VB: After conducting five 5-second combustion tests on the sample, the residual flame and residual flame will extinguish within 60 seconds. Dropping particles cannot ignite cotton. For block samples, it is allowed to be burned through.

　　5VA: After conducting five 5-second combustion tests on the sample, the residual flame and residual flame were extinguished within 30 seconds. Dropping particles cannot ignite cotton. It is not allowed to burn through block samples.

　　At present, the insulation shell of the terminal block needs to be selected with different levels of flame retardant and fireproof materials according to the requirements. For example, the Hengzhuoneng terminal block meets the flame retardant level determined by UL94 and complies with RoHS environmental protection requirements.