危險區域分為六大類，分別是 Zone 0、Zone 1、Zone 2、Zone 20、Zone 21、Zone 22，每一場域的條件說明如圖所示。
B. 設備保護等級 EPL (Equipment Protection Level) 分為 Ma、Ga、Da、Gb、Db、MB、Gc、Dc。
1.Ga (氣體)，Da (粉塵)，Ma (礦坑)
– Very high protection: the equipment remains safe in normal operation，even in rare fault situations (two faults at once)
2. Gb (氣體)，Db (粉塵)，Mb (礦坑)
– High protection: the equipment remains safe in normal operation, also when faults occur (single fault)。
3. Gc (氣體)，Dc (粉塵)
– Enhanced protection: the equipment remains safe in normal operation，and may have extra protection to minimize ignition risk in fault situations (fault may cause equipment to shut down)。
當材料的表面不論帶負電荷或正電荷時，若接觸任何不帶電荷的導電性物體，或是接觸帶有不同電荷的物體，都有可能導致累積靜電的放電：火花的產生。有些火花無害，但有些火花可能會點燃易燃蒸氣。非金屬外殼部份，採用特殊塑膠材料，Sabic 有幾種塑料系列 例如 SabicSTAT-KON and STAT-LOY 材料，針對防爆規格的需求，這些塑料都是可以被建議使用在產品機殼上的選項。
非金屬外殼特性的要求
a). 表面的電氣阻抗
Electrostatic discharges can initiate combustion or explosions。
b). 耐溫指引、防火等級、塑料耐溫規格要求 RTI
Flame class is based on safety’s requirement, IEC-60216 or UL746B RTI is the key requirement for explode-proof plastic material selection. (According to different EPL “Equipment Protection Level”requirement, and use service temperature + 20 (EPL Ga, Gb, Da, Db, Ma, Mb) or 10 (EPL Gc, Dc) deg)。
Ga, Da, Ma – very high protection: the equipment remains safe in normal operation，even in rare fault situations (two faults at once)。
Gb, Db, Mb – high protection; the equipment remains safe in normal operation，also when faults occur (single fault)。
Gc, Dc – enhanced protection: the equipment remains safe in normal operation, and may have extra protection to minimize ignition risk in fault situations (fault may cause equipment to shut down)。
The TI or RTI is important properties of non-metallic material，the TI or RTI is the temperature in °C，at which the properties have decreased to 50% of their initial value after a long-term exposure to this temperature。
RTI (相對熱指數) according to EPL must be 10 or 20 degree + than the product maximum service temperature。這是3C機構設計爸在前面的發表中，黃卡的內容也包括了RTI。
c). 抗UV規格
主要的是要符合 UL746C的 f1 認證其，次就是要符合ISO179 or ISO4892-2的測試要求。
UV light resistance, good weatherability，materials whose properties are not significantly degraded in any of these areas are considered to have passed and are suitable for outdoor use。
d). 塑料的顏色
Conductive fillers added which is to impact plastic material's color。(getting dark & black is the trend)。防爆塑料一般來說偏向黑色。
e). 抗低溫的材料能力
Related to product spec definition of operation temperature。
The product supports lower operating temperature, and it should be considered DBTT (Ductile to Brittle Transition Temperature 韌性到脆性轉變溫度) of material properties。
The material candidate STAT-LOY D3000IEU6 is good for low temperature requirement。
Surveyed material list (plastic)幾種surveyed的塑料供參考，有幾種塑料可以去 survey，如下，鎖定 Sabic 塑料。
Surface resistance requirement is defined in spec IEC-60079 as below shown, because electrostatic discharges can initiate combustion or explosions, so the material properties is between static dissipative composites to anti-static composites，the lower surface resistance will impact RF performance, there is a material considered for RF product use, the model name is STAT-LOY D3000IEU6，we need to be carefully if the product with RF function。
