Sundström SR597 ABEK1 Threaded Filter (Each)The SR 597 A1BE2K1 gas filter are intended for use in the SR 500 SR 500 EX fan. The filter type protect against the following gases vapours: Type A protects against organic gases and vapours, such as solvents, with boiling points > +65 C. Type B protects against inorganic gases and vapours, such as chlorine, hydrogen sulphide and hydrogen cyanide Type E protects against acidic gases and vapours, such as sulphur dioxide and hydrogen fluoride Type K