EN 169 sets the requirements for filters used in welding, cutting and related processes. A welding filter is marked with the shade number alone, with no prefix — for example 11 — which distinguishes it from UV (2 or 3) and IR (4) filters.
Choosing the shade number
The right shade depends on the process and the current. Too light a filter does not protect the eye; too dark a filter makes the welder lean in closer, which creates other risks.
| Process | Current (A) | Shade |
|---|---|---|
| Oxy-acetylene welding | — | 4–8 |
| Oxygen cutting | — | 5–8 |
| MMA (stick) | 40–200 | 10–12 |
| MIG / MAG | 100–300 | 11–13 |
| TIG | 20–150 | 10–12 |
| Plasma cutting | 40–150 | 11–13 |
For automatic darkening filters see EN 379, which defines switching time and the light and dark states. If a helper is present in the welding area, they need a filter too — typically one or two shades lighter.