First, a reactive agent neutralizes the slightly acidic creosote making it less corrosive to metal components and less flammable. Second, a dehydrator absorbs the oils and moisture contained in some forms of creosote. Third, a combustion inhibitor helps reduce the chance of chimney fires. Finally, a magnesium catalyst helps break down third-degree creosote when the flue is heated by normal use.
By simply squeezing the bottle pointed directly up the flue (with an upward draft) near the top if the firebox, the powder is carried up the chimney coating the entire surface of the flue and enabling the four components to start working.