We have had many discussions recently with facilities regarding the difference between kiln dried (KD) and heat treated (HT). The term "kiln dried" relates to the moisture content of wood which is typically defined as 19% or below. The term "Heat treated" relates to the core temperature of wood which needs to reach a minimum 133° F for at least 30 minutes in a controlled environment (i.e. a heat chamber or kiln). It is important to realize that wood used in the manufacture of WPM and WPM itself can meet one specification but not the other. If moisture content is the only concern, this can be reached without the required temperature needed to be considered heat treated. Likewise WPM can be heat treated but this process may not allow the wood to reach the minimum moisture content to be considered kiln dried. If you see wood or WPM marked with the term "KD-HT" this means it has met the requirements for both kiln drying (19% or below MC) and heat treating (133° F minimum for at least 30 minutes).

Note: The 133° F temperature can only be used after a verification study is completed on the heat chamber and thermocouples must be calibrated annually. Most facilities operate at 140° F thereby avoiding the above requirements. See ALSC WPM Enforcement Regulations 8.a 2  for more information.