... or coal-dust are present. ExdIIAT4 - safe for use 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 ...