A silencer apparatus for attenuating noise in gas flow systems. The apparatus generally includes a housing having an interior cavity and a gas flow inlet and outlet that are adapted to be connected to a passage such that a gas flowing through the passage enters and exits the cavity of the housing through the inlet and outlet, respectively. A silencer cartridge unit is removably disposed within the interior cavity of the housing and defines a gas flow path fluidically connected to the inlet and outlet of the housing. The silencer cartridge unit has at least one sound-attenuating element that surrounds the gas flow path. The housing is further equipped with a closure that sealingly closes a portion of the housing, and is releasable from the housing to provide an access opening through which the silencer cartridge unit can be removed. The apparatus can also be adapted to include a filtration medium.