Unalloyed steels and the pure nickel steels frequently used in the past can sustain significant damage from hydrogen attack in ammoniacal environments. The attack causes decarburization that leads to a loosening of the structure due to the precipitation of methane along grain boundaries. It occurs between 200 and 300 deg C, depending on hydrogen pressure. Parts of an apparatus that operate in these types of environments must be checked constantly if they are not made from hydrogen-resistant steel. The results of two such examinations serve to illustrate the challenges.