EN 14387 sets the requirements for gas filters and combined filters. Choosing the right one comes down to two questions: which substance is in the air (the type) and at what concentration (the class).
Filter types and colours
| Type | Colour | Protects against |
|---|---|---|
| A | Brown | Organic gases and vapours with boiling point >65 °C (solvents, paint) |
| B | Grey | Inorganic gases (chlorine, hydrogen sulphide, hydrogen cyanide) |
| E | Yellow | Acid gases (sulphur dioxide, hydrogen chloride) |
| K | Green | Ammonia and organic amines |
| AX | Brown | Organic compounds with boiling point ≤65 °C |
| Hg | Red | Mercury vapour (max 50 hours) |
| NO | Blue | Nitrogen oxides |
| P | White | Particles (in a combined filter) |
Capacity classes
- Class 1
- Low capacity — up to 0.1% by volume (1000 ppm)
- Class 2
- Medium capacity — up to 0.5% by volume (5000 ppm)
- Class 3
- High capacity — up to 1% by volume (10 000 ppm)
Combined filters
Where gas and particles are present together — spray painting, for instance — a combined filter is needed, marked A2P3 or ABEK1P3. The gas part is written first, the particle part second.
When to change it
Unlike a particle filter, an exhausted gas filter gives no warning through breathing resistance. The signals are smell or taste under the mask, eye or throat irritation, or the end of the manufacturer's stated service time. Once opened, a filter has a limited life even unused.