The flammability of tropical woods and the effect of a selected fire protection coating were evaluated using a cone calorimeter at a cone radiancy of 35 kW/m2. Three samples were from the South American continent (Cumaru, Garapa, Ipe), and two were from the Asian continent (Kempas and Merbau). Samples were treated with commercial fire retardant (FR) containing ferrous phosphate as an essential component. The untreated samples were used as reference materials that were of particular interest concerning their flammability. It was shown that there is unambiguous correlation between the effective heat of combustion (EHC) and total oxygen consumed (TOC) related to mass lost during burning for both the untreated and treated samples. In the case of Cumaru and Garapa, there exists an inverse relation between the amount of smoke and carbon residue. The decisive effect on the time of ignition was performed by the initial mass of the sample. This is valid for the spruce and the Cumaru, Ipe, and Kempas, both treated and untreated with retardant, while Garapa and Merbau were found to decline. According to the lower maximum average rate of heat emission (MARHE) parameter, a lower flammability was observed for the treated samples of wood, except for Garapa wood. Fire-retardant treated Garapa and Merbau also have a significantly lower time to ignition than untreated ones.

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The subject matter of the article is thermally modified tropical wood (Meranti and Merbau) and its reaction on fire. Thermal treatment of wood (thermal wood) is a new technology of wood treatment improving its physical and biological properties and increasing its resistance to biological wood destroying processes and atmospheric effects. The fire and technical properties of thermal wood, especially its reaction to fire, have not been studied sufficiently. The latter is the subject matter of this article. A comparison is made to describe the influence of process temperatures of the thermal modification of selected tropical woody plants. Experimental equipment was non-standardized laboratory equipment using a flame source of higher intensity (flame burner - propane-butane) affecting the test sample in an open environment. This is a simulation of an actual fire. The performance of the thermally treated wood (20 °C, 160 °C, 180 °C) is evaluated by measuring the weight loss and the burning rate. The results are presented in tables and diagrams and are statistically evaluated. This study investigated the effects of the thermal treatment of Merbau and Meranti wood on selected burning characteristics. The results obtained from raw (untreated) wood test specimens were compared to results obtained from the test specimens subjected to thermal treatment at 160 °C, 180 °C and 210 °C. The monitored characteristics were weight loss and the burn rate. The results showed that the thermal treatment of Merbau and Meranti wood significantly increased its flammability and accelerated its combustion. In addition, its burn rate was higher than in untreated wood, reflecting that it is necessary to add fire retardants to thermally treated Merbau and Meranti wood.