The occurrence of hydrogen attack related to the presence of methane in the steel cavities can be identified. This can be done by using the described annealing and metallographic testing procedure. To quantify the remaining safety of hydrogen-attacked industrial equipment, the degree of hydrogen damage can be measured by means of metallography, ultrasonic testing and chemical H-determination. A relation has been established between these different testing procedures. The fracture-mechanical properties of the damaged material have been determined. The results are expressed in terms of strength ratio. A first attempt is made to give an approximation of the remaining safety of the damaged material.