Modern Coating Approaches to Fire Safety in Wood Structures: A Review of Intumescent and Non-Intumescent Coatings

Non-intumescent flame-retardant coatings (NIFRCs) have become effective fire protection solutions for polymeric materials, especially rigid polyurethane foam (RPUF). Unlike intumescent coatings, NIFRCs do not expand when heated; instead, they create stable, inorganic-rich barriers that block heat transfer, delay ignition, and reduce smoke release. This review highlights progress in hydrogel, silica sol, aerogel, and ceramic-based NIFRCs. These developments show remarkable improvements, such as longer time to ignition, lower peak heat release rate, decreased total heat release rate, and less smoke production. The protecting mechanism includes water vapor cooling, char layer formation, and strong barrier effect. A comparison with intumescent coatings highlights the benefits of NIFRCs in durability, thickness, and smoke suppression, making it a promising option for sustainable fire-safe building materials.