Wood burners are desirable features in the home. However, for many years, in response of an increased population density in certain areas and increased environmental concerns, wood burners, such as wood-burning fireplaces and heaters have been increasingly regulated with respect to particulate and other emissions.
In recent years the quality of the air has received major consideration. Clean air has become more than a phrase. Significant efforts have been expended to minimize pollutants in the air we breathe. Some examples of these efforts include imposing emission standards on automobile exhausts, shutting down the use of incinerators in apartment houses, and designing or modifying large garbage burning incinerators to meet established standards.
Several of the compounds produced during the combustion of wood are of great concern to environmentalists and to environmental organizations, such as the Federal Government's Environmental Protection Agency (EPA), interested in maintaining, or in some cases establishing, clean air. The problem of air pollution caused by the compounds produced when wood burns has been recognized by many, and a growing number of state and local environmental agencies are considering the regulation of wood burning devices.
As a result of this concern, for example, emission standards for a majority of combustion processes have been established by the EPA. On Feb. 18, 1987, the Environmental Protection Agency (EPA) published in the Federal Register, Volume 52, No. 32, 40 CFR Part 60 entitled “Standards of Performance for New Stationary Sources, Standards of Performance for New Sources, Residential Wood Heaters.” These regulations were proposed to control the burgeoning wood stove and fireplace industry, which many believed was substantially adding to the air pollution problem in the United States. These pollutants are varied and many. The primary pollutants include particles of organic compounds, carbon monoxide, volatile organic compounds, and nitrous oxides.
A widespread lack of effective emission reduction devices and methods for many fireplaces and other wood burners has prompted agencies and governments in some areas of the country where emissions from wood burning units are increasingly problematic, to ban their use in times of air pollution. Overall, the number of days during which wood burning is banned is increasing, as are the number of communities that ban their use.
Several emission reduction devices have been suggested in the art. One such fireplace pollutant removal device of the prior art utilizes a filter, a fan, and a smoke detector. In operation, the filter is placed in the flue, the fan is positioned above the filter to draw the exhaust gases up through the filter, and the smoke detector is mounted in front of the fireplace. The smoke detector acts as a monitor of gases reflected from a clogged filter and provides an alarm when the filter needs cleaning. A method of removing the clogged filter provides a roll of thin filter-paper which is scrolled through the flue as segments of the filter-paper saturate with pollutants. This method, however, has perceived drawbacks. For instance, if the paper clogs, smoke may be emitted from the fireplace into the area adjacent to the wood burning chamber.
Another fireplace pollutant filter of the prior art utilizes a ceramic fiber duct positioned, along the flow path of the combustion products, between the combustion chamber and the flue. A first duct portion promotes secondary combustion of unburned products of combustion and a second duct portion directs products of combustion from the front of the combustion chamber to the flue. Though this device may remove some pollutants by the secondary combustion, many may enter the atmosphere due to an incomplete removal by the secondary combustion.
Although there are many catalytic devices designed to reduce pollutants in fluid streams, the backpressures created by these devices can be a design issue. The increased backpressure hinders the fireplace's draw, causing a variety of potential unacceptable consequences, including smoke backing up into the house under certain conditions. Several companies have produced catalytic secondary combustion chambers to reduce the amount of pollution, which while effective, nonetheless substantially increased the cost of the stove.
It is possible to produce a wood burner operating at a very high temperature that creates a condition to substantially reduce the amount of particulate material and air pollutants being emitted from wood burning. However, wood burners having a large firebox volume are more difficult to design in a cost-effective way to reduce particulates and emissions to meet EPA requirements. The problem lies, at least in part, in the difficulty of maintaining high combustion temperatures in all areas within the firebox, and especially when the unit is operated at a slow burn rate.
There is a demand therefore for a wood burner that meets requirements of the EPA emissions regulations. The present invention satisfies the demand.