This part of ISO 11114 specifies test methods and the evaluation of results from these tests in order to qualify steels suitable for use in the manufacture of gas cylinders (up to 3 000 l) for hydrogen and other embrittling gases. This part of ISO 11114 only applies to seamless steel gas cylinders. The requirements of this part of ISO 11114 are not applicable if at least one of the following conditions for the intended gas service is fulfilled 1): — the working pressure of the filled embrittling gas is less than 20 % of the test pressure of the cylinder; — the partial pressure of the filled embrittling gas of a gas mixture is less than 5 MPa (50 bar) in the case of hydrogen and other embrittling gases, with the exception of hydrogen sulphide and methyl mercaptan in which cases the partial pressure shall not exceed 0,25 MPa (2,5 bar).