Their constuction is based on fire-resistant doors with wooden panels. Furthermore they have additional stiffening reinforcements, fire lock with 6 or 9 moving steel safety pistons, 7 fixed steel safety pistons and thermoexpanding gaskets. They can be offered with a big range of finishings.
They are steel doors (with or without panels) with twin steel sheets 1.25 mm thickness and their appearance is similar to fire doors. At their inner side, lead sheet is fitted along their whole surface, so the entire opening is sealed against radiation. They are manufactued by heavy duty standards.