When it comes to wood burning fireplaces, there are two general approaches to meeting the EPA smoke emission limits: non-catalytic and catalytic combustion. Both approaches have proved effective, but there are performance differences.
Non-catalytic products do not use a catalyst, but have three internal characteristics that create a good environment for complete combustion. These are firebox insulation, a large baffle to produce a longer, hotter gas flow path, and pre-heated combustion air introduced through small holes above the fuel in the firebox. The baffle and some other internal parts of a non-catalytic stove will need replacement from time to time.
In catalytic combustion, the smoky exhaust is passed through a coated ceramic honeycomb inside the products where the smoke gases and particles ignite and burn. All catalytic products have a lever-operated catalyst bypass damper which is opened for starting and reloading. The catalytic honeycomb degrades over time and must be replaced, but its durability is largely determined by the operator. The catalyst can last more than six seasons if the stove is used properly; but if the stove is over-fired by using inappropriate fuel, or if regular cleaning and maintenance is not done, the catalyst may break down in as little as 2 years. Garbage or treated lumber should never be burned in a wood stove, insert or fireplace.