The one at Kiltybo, in County Mayo, is a quiet example of a type that has puzzled researchers for generations. A fulacht fia typically survives as a horseshoe-shaped or crescent mound of burnt and shattered stone, usually found close to a water source. The accepted interpretation is that these were ancient cooking sites, in use primarily during the Bronze Age, where water in a timber- or stone-lined trough was brought to the boil by dropping fire-heated stones into it. The stones crack with repeated heating and cooling, and over time the discarded fragments accumulate into the characteristic mound that marks the site today.

The Kiltybo example sits within a landscape that would have been familiar territory to Bronze Age communities moving through the west of Ireland, a region whose boglands have preserved countless traces of prehistoric activity simply by sealing them beneath layers of peat. The burnt mound is the monument's most visible feature, that slow accumulation of thermally fractured stone representing not a single event but repeated use over what may have been a very long period. Some fulachtaí fia show evidence of use spanning centuries, suggesting they were not temporary camps but established places in the routine of local life. Whether they served purely as cooking sites, or also as locations for hide-working, textile processing, or bathing, remains a matter of active discussion among archaeologists, and Kiltybo, like most of its counterparts, does not yet offer a clear answer.