... in plants where the explosive mixtures of IIA Class, TI, T2, T3 or T4 are present. ExIIBT4 - safe for use in plants ... where the explosive mixtures of IIB Class, TI, T2, T3 or T4 are present. ExdIICT4 - safe for use in plants ... where the explosive mixtures of IIC Class, TI, T2, T3 or T4 are present. 1. Ambinent tempertuer should not be ...