An inventive apparatus for reducing emissions from a wood heater comprises (i) two or more volumes of a porous, catalyst-coated medium and (ii) one or more holders for the catalyst-coated medium. The one or more holders are structurally arranged to hold the volumes of the catalyst-coated medium in a specified spatial arrangement within an exhaust flue of the wood heater. The catalytic media are sized and shaped so that, in that specified spatial arrangement, the volumes obstruct substantially all straight-line paths from a combustion chamber of the wood heater through the exhaust flue past the volumes of the catalyst-coated medium. In the specified spatial arrangement, the volumes also leave unobstructed at least one tortuous exhaust gas flow path from the combustion chamber through the exhaust flue around and past the volumes of the catalyst-coated medium.
