Used primarily as a heat transfer agent in industrial systems due to its thermal stability and low flammability. Found in older cooling and heating equipment, especially in closed-loop systems where consistent performance under high temperatures is required. Also served as a dielectric fluid in certain electrical transformers and capacitors, though this use has declined due to environmental and toxicity concerns. Its persistence and potential to bioaccumulate have led to strict regulations, limiting current applications and requiring careful handling and disposal in legacy systems.