Oil thermal treatment, first developed by German scientists, is a promising technology for improving the durability and dimensional stability of wood for outdoor above-ground residential uses such as siding and shingles. The present authors’ previous research showed that 220ºC is an optimal treatment temperature, with 2 hours’ treatment producing wood with significantly improved moisture and biological resistance. This paper mainly deals with the preliminary investigation into fire, flame resistance and related thermal properties of such thermally modified wood. Slack wax and soybean oil were used as heating media for treatment at 220 ºC. Small-scale fire and flame resistance tests including the crib test and the two-foot tunnel test, were carried out. DSC (Differential Scanning Calorimeter) and TGA (Thermogravimetric Analysis) were also used to investigate the corresponding thermal properties. The results indicated that the oil-thermal treatment reduced the flame resistance, as a result of the oil or wax residue in wood surface, and wax absorbed by wood during the high-temperature treatment may facilitate extra heat evolution during thermal decomposition in air. However, in general, oil thermally-treated wood, especially soybean oil-treated wood, did not reduce the fire resistance of wood or affect the thermal properties of wood significantly.

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