While
the external appearance of some wood stoves hasn't changed much, the insides of
today's wood stoves are radically different. This is because manufacturers
had to develop sophisticated new technologies to meet federal clean air
standards.
What you should know when buying a wood stove or wood-burning insert
While
the external appearance of some wood stoves hasn't changed much, the insides of
today's wood stoves are radically different. This is because manufacturers
had to develop sophisticated new technologies to meet federal clean air
standards.
Wood stoves are the only consumer product other than automobiles that have a Federal
Emissions Standard. So, all wood stoves and wood inserts now
comply with rigid particulate emissions standards set by the Environmental
Protection Agency (EPA).
Particulate is basically unburned gases from the firewood. It either
condenses on the chimney wall where it can form dangerous creosote or it
released into the atmosphere as smoke, creating air pollution problems in some
locations. The EPA certified wood stoves burn all these gases before they
leave the fire box.
Recently,
emissions from wood stoves have been reduced by more than 90%, a staggering
improvement. There are two ways to achieve this tremendous
combustion efficiency. One technique is to force all gases though a catalytic
combustor before they leave the stove. Similar to what is now
used in automobiles, a wood stove catalytic combustor is a ceramic, honeycomb
shaped substrate coated with platinum or other precious metal. It lowers
the temperature at which smoke will burn, resulting in a very clean burn.
The other technology is known as "non-catalytic" or "high-tech". These units have perfected the balancing of time, temperature and turbulence; the "Three Ts" needed for combustion. The firebox is insulated, especially at the top, so that high internal temperatures are created. Judicious introduction of heated combustion air creates additional turbulence, and a series of baffles increases the "residence time" of air and gases in the stove.
Both clean-burning technologies have proven themselves, but there are differences. Non-Catalytic burners tend to start more rapidly and are more responsive. Catalytic units generally have a larger firebox and slightly higher efficiencies with corresponding lower emissions, however, the combustor needs to be replaced on average every five years and can be damaged by improper burning.