Why Wood Gasification?


Unforgettable Fire™ logo

Pyrolysis: A Fancy Name For Wood Gasification

The process of releasing wood gas (i.e. smoke) from wood is called “pyrolysis” which the dictionary defines as, “decomposition brought about by high temperatures“. During pyrolysis in an Unforgettable Fire™ wood stove, live flames will gradually diminish in size and intensity as the wood gas is spent by burning the load of wood, leaving behind embers which will continue to radiate heat, until they too have extinguishedor until another load of wood is added to the combustion chamber to begin the burning cycle again.

The gasification wood stoves by Unforgettable Fire™ utilize patented two-stage combustion technology. This patented technology restricts oxygen in the lower part of the combustion chamber, resulting in a slow and smoldering fire. This effectively vaporizes the wood and deliberately creates wood smoke. The wood smoke is then re-burned as fuel in the upper part of the combustion chamber before the smoke can exit the stove and the chimney.

This patented two-stage combustion results in a lower chimney temperature as less heat is lost up the chimney. While traditional wood stoves are very effective at heating your home, a great deal of heat unavoidably escapes up the chimney. We know this to be true because all EPA/CSA Certified wood stoves except for the gasification wood stoves manufactured by Unforgettable Fire™ require Class A manufactured chimney pipe for the entire length of the chimney—or the use of a masonry chimney, which can also withstand the high flue temperatures which result from burning wood by traditional means.

Less heat wasted up your chimney means more heat remains in your home to warm your family, and may also reduce the amount of wood that you need to cut and burn each year.


Unforgettable Fire™ logo

Our Unique Chimney System

The Unforgettable Fire™ gasifier wood stoves are the only EPA/CSA Certified wood stoves that have been UL-approved to vent with pellet pipe. This is possible because the patented gasification technology used in the Unforgettable Fire™ wood stoves results in lower flue temperatures. To be clear, all other wood stoves require Class A chimney pipe, or a masonry chimney, for the entire length of the chimney. In a residential application, the Unforgettable Fire™ gasification wood stoves require that pellet pipe is sleeved by a short section of Class A pipe that extends from the ceiling through the roof. It is the pellet pipe which carries the flue exhaust from the stove and the two types of pipe do not connect.

Because pellet pipe is far less costly than Class A chimney pipe, our unique UL-approved venting system can often save our clients hundreds of dollars on a new installation as compared with a new installation of a traditional combustion wood stove which requires Class A pipe for the entire length of the chimney. 

The relationship between any wood stove and its chimney is very similar to the relationship of the lungs and heart in the human body. When the lungs are not able to breathe properly, the performance of the heart suffers. Likewise, when the chimney does not draw properly, the performance of the stove suffers.

It is critical to the function of any wood stove that the chimney be warm enough to breathe properly; this requirement is not unique to the Unforgettable Fire™ wood stoves. Because our patented gasification technology results in significantly lower flue temperatures, our greatest challenge in colder climates was to keep our interior flue temperatures sufficiently warm enough to draw properly. We overcame this issue with good ‘ol American ingenuity and developed insulated pellet pipe.. For this reason we sell our Unforgettable Fire™ wood stoves as a package with our custom-manufactured insulated pellet pipe.

Although Unforgettable Fire™ has never performed any documented tests to back up our marketing claim that the Unforgettable Fire™ gasifier wood stoves “squeeze more heat from less wood”, many of our clients have reported to us that they burn far less wood than they burned in their previous wood stove. The reason is simple: with less heat escaping up the chimney, more heat remains in the house to keep your family warm. With less heat escaping up the chimney with more heat in the house, you can potentially cut and split less wood for each heating season.

As you can imagine, the EPA/CSA Certification testing and UL-safety testing are highly controlled and regulated. Consumer results will vary, as there are many factors which can affect the amount of heat that can be produced in any wood stove, including the species of the wood, the moisture content of the wood, size of the load, the frequency of the loads, the brand of the previous wood stove that was replaced, along with its model, age and condition, as well as the chimney. Understandably, it would be impossible for any wood stove manufacturer to test the performance of each of their models against all other stoves in existence, so we are only able to report the results of the EPA/CSA Certification and UL-safety testing through our Owner’s Manuals, and share with you in good faith what our clients have reported to us.


Unforgettable Fire™ logo

Burn Time & Heat Output

As with any wood stove, there are many variables that can affect burn times and heat output. Softwoods such as Douglas Fir and pine will burn more quickly than hardwoods such as oak, ash, hickory, maple, or madrone. The temperature of your space will be determined by many factors including the square footage and ceiling height, the stove’s placement, the size and frequency of your loads of wood, the species and moisture content of your wood, and the ability of your space to retain heat. The ability of your space to retain heat is influenced by local climate and weather conditions, quality and thickness of insulation, the number and size of windows, window quality, air flow within your home and humidity levels. 

Burning dry, seasoned wood of 20% moisture content or less will result in the optimal gasification of your wood, more heat, longer burn times, and less creosote than wood containing greater than 20% moisture content. Your investment in a moisture meter with an accuracy of +/- 1% will help you get the most heat from the least amount of wood.

For approved installation instructions and diagrams, consult the Unforgettable Fire™ Owner’s Manuals regarding your specific application. For additional questions, call 1-855-872-7868 during normal business hours.