In 1950 Geißel became head of the Hamburg branch of the , instigating a Crisis Response section ("Katastrophenhilfe"), informally as a response to the catastrophic floods in the Netherlands in 1953, and founded formally in 1954. In 1955 he moved to the organisation's national head office in Stuttgart, taking charge of the Crisis Response section nationally. Following the merger of the with the church sponsored evangelical Inner mission, in 1957 he was appointed director of the combined organisation, still based in Stuttgart. His responsibilities encompassed finance, crisis response and administration. In 1972 he was appointed vice-president of what had by now evolved into Diakonischen Werkes der EKD e.V.. He retired in 1982, but continued to contribute in an advisory capacity.