An apparatus and method for collecting fluid from a drill string or borehole casing includes a collection casing having means for sealably engaging around a drill string or borehole casing to create a chamber between the interior of the collection casing and the drill string or borehole casing, and one or more fluid nozzles for directing cleaning fluid into the interior of the chamber. The one or more nozzles are configured to direct cleaning fluid to impact the inwardly facing interior surface of the collection casing.