Table 1

 RPE filter types

SubstancesFilter type; commentCasing
*Gas and vapour filters are available with three capacities: 1, lowest; 3, highest.
ParticulateP1 Low efficiency P2 Medium efficiency P3 High efficiencyWhite
Organic gases with boiling points >65°C as specified by manufacturerA1, A2, A3*Brown
Inorganic gases and vapours as specified by manufacturer, excluding carbon monoxideB1, B2, B3*Grey
Sulphur dioxide and other acid gases and vapours as specified by manufacturerE1, E2, E3*Yellow
Ammonia and organic ammonia derivatives as specified by manufacturerK1, K2, K3*Green
MercuryMust incorporate a P3 filterRed–white
Oxides of nitrogenNO must incorporate a P3 filter, single use onlyBlue–white
Organic gases with boiling points <65°C as specified by manufacturerAXBrown
Filters against specific substances as specified by manufacturerSX, marked with name of chemicalViolet