Thermally modified wood is wood that has been modified by a process of wood being heated (> 180 °C) in absence of oxygen inducing some changes to the chemical structures of cell wall components (lignin, cellulose and hemicellulose) in the wood in order to increase its durability and dimensional stability. But all this does not turn thermowood fire-proof.
Thermo-treated wood suits well for interior and exterior cladding, terraces and floors, furniture and furnishing. But being a wood with altered properties means also that making thermowood fire-proof requires a specific fire retardant, tested and certified on thermowood. The certificates issued for regular wood do not apply on thermowood.