In this work, we have studied the degradation processes of polyurethane containing phosphonate groups used as a fireproofing agent. These studies are undertaken by simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC) measurements. It is found that fireproofing agents with phosphonate react with oxygen in the air and prevent the complete combustion of the material. It is also found that the energy released during combustion is low when comparison is performed with other fireproofing materials.