Particleboards containing waste rubber (tires and mixtures of isolators and carpets) filler were evaluated from the point of view of its flammability. The assessment of the utilization of these composites in the construction industry was analyzed through the determination of their spontaneous ignition temperatures, mass burning rate and calorific value. Based on the results of spontaneous ignition temperatures, similar values between particleboards and particleboards containing 10%, 15% and 20% of waste tires were obtained. The average time was from 298 s to 309 s and the average temperature was from 428.1 °C to 431.7 °C. For the mass burning rate, there were similar results between particleboards and particleboards containing 10% of waste tires and waste rubber. The time to initiation was 34 s and the time to reaching a maximal burning rate was from 66 s to 68 s. The calorimetry results showed similar properties for the calorimetric value and ash content in particleboards and particleboards containing 10% of waste tires and waste rubber. The calorific value was from 18.4 MJ·kg⁻¹ to 19.7 MJ·kg⁻¹ and the ash content from 0.5% to 2.9%.

The paper assesses the influence of the heat flux on spruce wood (Picea abies L.) behavior. The heat flux was performed at 15, 20, 25, and 30 kW·m⁻². The fire-technical properties, such as the mass burning rate, charring thickness, charring rate, as well as the chemical composition (contents of the extractives, lignin, cellulose, holocellulose), of wood were determined. The highest burning rate of spruce wood of 0.32%·s⁻¹ was reached at the heat flux of 30 kW·m⁻². The charring rate ranged from 1.004 mm·min⁻¹ (15 kW·m⁻²) to 2.016 mm·min⁻¹ (30 kW·m⁻²). The proposed model of the charring process of spruce wood in time and appropriate thickness as a selected parameter is applicable in validation of the results of computer fire models in the design of fire protection of wooden buildings. The decrease in the holocellulose content mostly caused by the degradation of hemicelluloses was observed during thermal loading. The biggest decrease in hemicelluloses (24.94%) was recorded in samples loaded at 30 kW·m⁻². The contents of cellulose increased due to the structural changes (carbonization and crosslinking), the content of lignin increased as well due to its higher thermal stability compared to saccharides, as well as the resulting lignin condensation.

The paper deals with the assessment of the age of oak wood (0, 10, 40, 80 and 120 years) on its fire resistance. Chemical composition of wood (extractives, cellulose, holocellulose, lignin) was determined by wet chemistry methods and elementary analysis was performed according to ISO standards. From the fire-technical properties, the flame ignition and the spontaneous ignition temperature (including calculated activation energy) and mass burning rate were evaluated. The lignin content does not change, the content of extractives and cellulose is higher and the content of holocellulose decreases with the higher age of wood. The elementary analysis shows the lowest proportion content of nitrogen, sulfur, phosphor and the highest content of carbon in the oldest wood. Values of flame ignition and spontaneous ignition temperature for individual samples were very similar. The activation energy ranged from 42.4 kJ·mol⁻¹ (120-year-old) to 50.7 kJ·mol⁻¹ (40-year-old), and the burning rate varied from 0.2992%·s⁻¹ (80-year-old) to 0.4965%·s⁻¹ (10-year-old). The difference among the values of spontaneous ignition activation energy is clear evidence of higher resistance to initiation of older wood (40- and 80-year-old) in comparison with the younger oak wood (0- and 10-year-old). The oldest sample is the least thermally resistant due to the different chemical composition compared to the younger wood.

This study evaluated the fire properties of various particleboard (PB) types, including those made from sound spruce particles, degraded wood (brown and white rot), and recycled materials (blockboard, pallets, thermally modified wood, raw and laminated PBs, or mixtures). Laboratory-manufactured PBs showed densities ranging from 587 to 654 kg·m⁻³, with higher densities generally correlating with longer ignition times, although no statistically significant relationship was observed. Ignition times varied depending on material composition, with PBs made from sound spruce particles exhibiting the longest ignition times (103 ± 4.89 s). In contrast, PBs containing recycled or degraded particles ignited faster, influenced by additives such as adhesives and laminates. The burning rate peaked between 90 and 180 s, with PBs containing recycled raw PB particles and those degraded by brown rot showing the highest maximum burning rates (0.214 and 0.213 %·s⁻¹, respectively). Recycled laminated PBs reached peak burning rates in the shortest time, while control PBs required the longest time. Mass loss was higher in PBs with recycled or degraded particles, ranging from 47.52% to 51.71%, compared to 44.89% for control PBs. These findings highlight the trade-offs between fire resistance and the use of recycled materials, emphasizing the impact of additives on combustion behavior.

The study investigates the determination of selected fire properties of spruce wood, specifically the charring rate, using a modified testing method described and registered at the Industrial Property Office of the Slovak Republic PUV 50121-2020, utility model no. 9373. The samples were exposed to a square ceramic infrared heater, FTE-750W, with a power output of 750 W, using which we determined the heat flux as a function of voltage (V). Spruce wood specimens with dimensions of 75 mm × 75 mm × 50 mm (l × w × h) were subjected to thermal exposure under heat fluxes of 10, 15, 20, and 25 kW∙m⁻². The charring rate was evaluated using two distinct approaches: the first method measured the thickness of the char layer formed after a duration of 1800 s, while the second method was based on reaching a temperature threshold of 300 °C. The findings demonstrated a positive correlation between the thermal load and the charring rate. The charring rates obtained using the first method ranged from 0.2397 to 0.6933 mm∙min⁻¹, whereas those derived from the second method varied from 0 to 1.0344 mm∙min⁻¹. This suggests that the 300 °C temperature criterion may not be a reliable parameter for calculating the charring rate. The precision of the results was corroborated through numerical simulations.

Selected fire properties of oak wood (mass loss, burning rate, and charring rate) and its chemical composition (extraction substances, lignin, cellulose, hemicellulose) were assessed. Oak wood samples with dimensions of 50 × 40 × 50 mm (l × w × t) were thermally loaded by a heat flux of 15, 20, 25, and 30 kW·m-2, using a ceramic infrared heater with a power of 1000 W. At the given thermal loading, the mass loss ranged from 26% to 47%, whereas the burning rate ranged from 0.0365 to 0.0584%·s-1. The maximum thickness of charred layer was 20 mm, and the charring rate reached values from 0.65 to 0.87 mm·min-1, in a time interval of 1800 s. With increasing thermal loading, the content of extraction substances increased by 30% and the content of lignin increased slightly as well. In contrast, the content of hemicelluloses decreased by 10.3%. This indicates that hemicelluloses are the least thermally resistant wood component. The obtained results can be used as basic data for future testing using medium-sized tests. Subsequently, they can be compared with the input parameters for calculating the fire resistance of wooden constructions elements, which will be the subject of further research.