This TECDOC is the first publication on safety classification of components for fusion applications. It highlights the existing differences between fission and fusion reactors in identification and classification of structures, systems and components that are important to safety and offers guidance for fusion applications. The publication also provides guidance on inclusion of the new design extension conditions, which have been added after the review of IAEA Safety Guides following the Fukushima Daiichi NPP accident. The International Atomic Energy Agency (IAEA) is the world's center of cooperation in the nuclear field. It was set up as the world's "Atom's for Peace" organization in 1957 within the United Nations family. The Agency works with its Member States and multiple partners worldwide to promote safe, secure and peaceful nuclear technologies.