3 hour flame (Variations in fireplace and climatic conditions may alter duration of burn). Burns up to 3 hours (Variations in fireplace and climatic conditions may alter duration of burn). Burns cleaner than wood (15th Emission Inventory Conference, New Orleans, May 2006). Up to 75% less particular matter (15th Emission Inventory Conference, New Orleans, May 2006). Up to 80% less carbon monoxide (15th Emission Inventory Conference, New Orleans, May 2006). This firelog is made from recycled biomass product such as wood sawdust, ground tree nutshells, and blended wax. For use in solid fuel burning masonry fireplaces, listed factory built fireplaces, and fireplace inserts. Unconditional guarantee.