... 2, IIA, IIB group explosive atmosphere.Three, explosion-proof, explosion-proof acoustooptic alarm alarm alarm alarm, price, technical parameters: ... 9mm to 14mmTwo, explosion-proof, explosion-proof alarm audible and visual alarm, explosion-proof lamps explosion-proof alarm features:1, cast aluminum ... Alarm is also installed with inner and outer ground screw, when in use must be grounded reliably.2, ...