1, ia class: in normal operation, one fault and two faults can not ignite the explosive gas mixture of electrical equipment. In normal operation, the safety factor is 2.0; a fault, the safety factor is 1.5; two faults, the safety factor is 1.0.
2, ib class: in normal operation and a fault can not ignite the explosive gas mixture of electrical equipment. Normal operation, the safety factor is 2.0; a fault, the safety factor is 1.5. normal operation, spark contacts shall be added to the explosion-proof enclosure or gas-tight enclosure protection, and fault self-display measures, a fault safety factor is 1.0.