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Respirator filters (A, B, E, K and P)

Respirator filters for half and full masks are distinguished by type and class. Gas filters (A, B, E, K) protect against certain gases and vapours and carry identification colours, while particle filters (P) protect against dust, smoke and mist. The class 1, 2 or 3 states the performance. Combination filters such as A2P3 combine both.

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When is this relevant?

Relevant for work with solvents, acids, vapours and fine dusts. Which filter is suitable depends on the substance and its concentration and follows from the risk assessment.

Gas filters

  • A, brown: organic gases and vapours with a boiling point above 65 °C
  • AX, brown: low-boiling organic compounds with a boiling point up to 65 °C, for single use only
  • B, grey: inorganic gases and vapours, for example chlorine and hydrogen cyanide, not carbon monoxide
  • E, yellow: sulphur dioxide, hydrogen chloride and other acid gases
  • K, green: ammonia and organic ammonia derivatives

Classes of gas filters

Gas filters come in classes 1 (low), 2 (medium) and 3 (high capacity). The class depends on the maximum possible concentration of the gas. For class 1 the limit of use is 0.1 vol.-% (1000 ml/m³), for class 2 it is 0.5 vol.-% (5000 ml/m³).

Particle filters

  • P1: separation efficiency of at least 80 %
  • P2: separation efficiency of at least 94 %
  • P3: separation efficiency of at least 99.95 %

Particle filters are marked white and do not work against gases and vapours. For half masks, the limit is 4, 10 and 30 times the occupational exposure limit. NR means that repeated use is limited to one shift at most, R permits use beyond one shift.

Combination filters

A combination filter such as A2P3 protects at the same time against organic vapours of class 2 and particles of class P3. For mixtures, combination filters or multi-range filters such as ABEK help. The end of shelf life is stated on filters.

Sources

  • Haufe: Choosing the right respiratory protection, filters
  • BG BAU: Module e 603 (respirator filters)
  • Dräger: Filter chart
  • Suva: Selection guide for particle and gas filters
  • EN 14387 and EN 143

Last updated: · This explanation is for general information and does not replace legal advice.