Fire-retardant wood is treated with which substance?

Fire-retardant wood is treated with mineral salts to enhance its fire resistance. Mineral salts act as a flame retardant by altering the way the wood reacts to heat. When exposed to fire, the treated wood can inhibit combustion and reduce flame spread by forming a char layer that protects the underlying material. This treatment is effective in preventing the wood from igniting easily and helps to slow down the progression of a fire.

While aluminum oxide, calcium sulfate, and urea may have various applications in other contexts, they do not serve the same purpose as mineral salts in the treatment of wood to increase fire resistance. Mineral salts are specifically formulated for this application, making them the preferred choice for producing fire-retardant wood.