TIMBER PRODUCTS May Newsletter Volume: 05/05/2017

The Heat Chamber Verification Study

Almost all WPM that meets ISPM 15 standards has been treated through the use of heat.  If a facility wants to run a heat chamber at a lower temperature than what is prescribed by ALSC, a verification study is required.  This verification study requires an agency to use special equipment to use 9 -12 probes in the chamber being studied to determine the coldest zones and ensure the chamber along with other related equipment are operating properly.  There are three conditions under which a verification study is required for a heat chamber.

1. Heat chambers using only dry heat which utilize one or more schedules that do not maintain an operating temperature of 160°F or greater (not including ramping temperature).  If you have a wet and dry bulb in a heat chamber that only uses dry heat you still need to maintain 160°F or greater since there is no steam being introduced.  The dry bulb is used to determine the temperature and the wet bulb temperature reading is disregarded.
2. Heat chambers using both dry and wet heat (steam) which utilize one of more schedules that do not maintain a wet bulb temperature of at least 140°F of greater (not including ramping temperature).  Determination for a verification study in this situation is based solely on the wet bulb temperature reading and the dry bulb temperature reading is disregarded.
3. Heat chambers using no set schedule, but instead using thermocouples inserted directly into wood which do not maintain a core temperature of 140°F or greater.  Typically 3 thermocouples are used by a facility in this scenario and placed in the coldest zones of the chamber.  

When a verification study is performed, the temperatures required must be attainable in a reasonable period of time and any equipment variance of more than plus or minus 5°F will require recalibration or replacement.  The verification study is performed at an additional cost to the facility but some companies believe this cost can be recouped in the energy savings made by running at a lower temperature.  However most companies run at the minimum temperatures mentioned above to avoid the cost of the verification study.  Once a verification study is completed, a copy of the results must be maintained at both the agency and facility locations.  Facilities treating multiple types of WPM where the airflow and cold zones could be affected may need to have several verification studies completed. 

If your facility is interested in a verification study for you heat chamber, please contact your inspector or the TP main office.