Shenhai Explosion-Proof
If an area requires the installation of dust explosion-proof electrical devices, the explosion-proof standards for equipment in Zone 20 must exceed those required for Zones 21 and 22.
| Zone 20 | Zone 21 | Zone 22 |
|---|---|---|
| An explosive environment in the air that continuously appears in the form of combustible dust clouds, exists for a long time or frequently. | Places where explosive environments in the air may appear or occasionally appear in the form of combustible dust clouds during normal operation. | In the normal operation process, an explosive environment in the air in the form of combustible dust clouds is impossible to occur in places where the instrument exists for a short period of time. |
Specifically, in Zone 20, only intrinsically safe or encapsulated devices are permissible, while flameproof devices are not allowed.