Intumescent fire retardant coatings are one of the most frequent passive fire protection methods used for structures in case of wildland or Wildland-Urban Interface (WUI) fires. When exposed to a heating source, they form a thick layer of carbon-rich char on the exterior surface of a structure and can delay or event prevent the structure's ignition. These coatings are economical and easy to apply. However, the performance of such systems is affected by weathering, as aging affects the intumescence mechanism and fire protection effectiveness. Moreover, coatings may act as an additional source of fuel to the structures after weathering. In this study, three intumescent coatings were selected from the market to compare their fire protection performance after weathering. A bench-scale cone calorimeter was used to collect data for fifteen different classes of samples. The classes include the samples which were exposed to natural weathering for 0, 3, 6 and 12 months in two different weathering orientations (north and south). Then, the specimens were randomly picked up from each class and were tested using the cone calorimeter. The Analysis of Variance (ANOVA) method as a statistical tool was then employed to analyze the differences among the classes. First, the uncoated and coated specimens were compared. In all cases, coatings showed a significant protection. Then, coated specimens with different weathering intervals were compared. The results showed that not all coatings preserved their protective effectiveness after 3 months of weathering exposure. In some cases, there were no statistical evidence of performance difference between coated and uncoated specimens just after 3 months.
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