The one recorded at Carnaun in County Clare is a single example of a type that has puzzled archaeologists for generations. A fulacht fia typically survives as a horseshoe-shaped or kidney-shaped mound of fire-cracked stone and charcoal-blackened earth, the accumulated debris of repeated heating episodes. The stones were heated in a fire and then plunged into a water-filled trough, bringing the water rapidly to the boil. What exactly this process was used for, whether cooking, textile processing, bathing, or something else entirely, remains a matter of genuine debate.

The majority of fulachtaí fia in Ireland date to the Bronze Age, roughly 2000 to 500 BC, though some have produced earlier or later dates through radiocarbon analysis. They are almost invariably found close to a water source, a stream, a spring, or a boggy hollow, which would have supplied the trough. The Carnaun example sits within a county that has no shortage of prehistoric activity, from the limestone pavements of the Burren with their wedge tombs and portal dolmens, to ringforts and souterrains scattered across the inland townlands. Clare's geology and its relatively low level of intensive modern agriculture have helped preserve monuments that elsewhere have been ploughed away or built over.