Time and Temperature Curve to Kill Bugs
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Here's a little basic info on bug killing with heat in thicker pieces of wood in the kiln. June 22, 2012
Question
Are there any charts or formulas showing the time it takes for heat to penetrate thicknesses of wood at specified temperatures? I have searched the net but must not be using the right search words.
Specifically I would link to know how long I would need to maintain 140 degrees to reach the core of a 10/4 board with 130 degrees in order to kill PPB/eggs? Also, how long if the temp were raised to 150 degrees? If I had such a chart/formula in the future I could use it for different thicknesses/temps.
Forum Responses
(Sawing and Drying Forum)
From the original questioner:
The wood is pecan (hickory) and it is air dried to 12 percent.
From contributor Z:
Boards that are average 3"x 6" take about eight hours at 140 degrees, and about six hours at 150 degrees. Boards that are average 3"x 10" take about nine hours at 140 degrees, and about six and a half hours at 150 degrees.
From contributor Z:
By the way - species, length, or current moisture content has nothing to do with how long it takes to kill bugs. It is all to do with how thick and wide your product is.
AI enhanced answer (added Apr 01, 2025):To effectively kill bugs in thicker pieces of wood using heat in a kiln:
1.
Temperature: Set the kiln to achieve a core temperature of at least 130°F (54°C) for several hours. This temperature is lethal to most wood-boring insects and their eggs.
2.
Duration: The wood should be held at this temperature for a minimum of 30 minutes to an hour, but for thicker pieces, extend this time to ensure heat penetration. A rule of thumb is 1 hour per inch of wood thickness.
3.
Moisture Content: Lower the moisture content of the wood to below 20% before heat treatment. This reduces the insulating effect of water, allowing heat to penetrate more effectively.
4.
Heat Distribution: Ensure even heat distribution within the kiln. Use fans or air circulation systems to prevent cold spots where bugs might survive.
5.
Monitoring: Use probes to monitor the internal temperature of the wood. This is crucial for thicker pieces to confirm that the heat has reached the core.
6.
Cool Down: After treatment, allow the wood to cool down slowly to avoid cracking.
This method ensures that pests are eradicated without compromising the integrity of the wood, making it safe for use in construction or furniture making.
