CY-VH03 explosion-proof VHF is intrinsic safety type, the explosion-proof marks: Ex ib Ⅱb T4 Gb, meet the MSC. 338 (91) - IMO Resolution MSC.338(91):Adoption of Amendments to the International Convention for the Safety of Life at Sea, 1974, as amended, suitable for firefighters on the ship. When the VHF use for firefighters, the VHF may be equipped with CY-HS1518 (Throat Microphone headset) or CY-HS1519 (Bone conduction headset). This explosion-proof VHF can used for chemical tanker and also use for explosive atmospheres, meet the demand of daily communication. The following is 4 type of explosion-proof headset: Ambient temperature: -20℃～+40℃ Atmospheric pressure: 80kPa～110kPa Standard oxygen content in the air : 21%( volume ratio) Relative humidity: 5%～95％（ when 25℃） Exist or maybe exist explosion - hazardous areas consisted of inflammable gas, Steam and air mixture of IIA-IIB class, T1-T4 group.