The factory was built on a site consisting of mainly sandhills and sand dunes to provide some protection against damage caused by an explosion.
[2] After the end of World War I, it closed and the administration building became a convalescence home for children from the families of unemployed miners.
It opened in December 1939 under the control of the Ministry of Supply as one of several explosive Royal Ordnance Factories making TNT.
[citation needed] After the end of World War II, it continued to manufacture TNT and tetryl for military use; and ammonium nitrate for agricultural use as a fertiliser.
[citation needed] From 1944 onwards, ROF Pembrey undertook breakdown of surplus ammunition, such as 4.5 inch anti-aircraft shells and 500 lb (230 kg) bombs.