The order of explosion-proof ratings is straightforwardly recorded as A < B < C.
| III | C | T 135°C | Db | IP65 |
|---|---|---|---|---|
| III Surface dust | T1 450°C | Ma | IP65 | |
| T2 300°C | Mb | |||
| T3 200°C | ||||
| A Flammable flying flocs | Da | |||
| T4 135°C | ||||
| Db | ||||
| B Non conductive dust | T2 100°C | Dc | ||
| C Conductive dust | T6 85°C |
For the ‘T’ rating, it’s remembered by its numerical order: the larger the number, the higher and safer the rating.
Therefore, an explosion-proof rating of BT4 surpasses that of AT2.
It’s important to clarify that ‘T’ denotes the maximum surface temperature of electrical devices. A T4 rating, set at 135°C, is applicable for explosive gases with flash points exceeding 135°C.
