Passive flue-gas silencers from KW use a porous mineral fiber as a sound absorber and can reduce noise by up to 25 dB. Passive silencers are suitable for use with all regular combustion heating appliances and can be used on condensing boilers without restriction. The silencers are available in straight or elbow configuration up to 14”. These passive silencers optimum absorption is in the 1000 Hz to 2000 Hz range. For low frequency absorption, we offer an available Low Frequency Silencer. For more significant sound issues you can connect multiple silencers as a modular system.