This International Standard specifies the sampling and analytical procedure for the determination of diffusible and residual hydrogen in ferritic weld metal arising from the welding of ferritic steel using arc welding processes with filler metal. Collection of the hydrogen over mercury is the primary method. Provided that the weld specimen size is maintained within limits dictated by the size of the test block, variations in welding parameters are permissible in order to investigate the effect of such variables on the weld hydrogen content. The techniques described in this International Standard constitute a reference method which should be used in cases of dispute.