A violent explosion ripped through a chemical site during destruction of the installation’s chimney. Two employees from the demolition company were positioned on a platform inside the chimney, some 35 m high, when the explosion reached the chimney, causing both to fall to their deaths. A spark might have suddenly triggered the ignition of chemical products impregnated into the chimney (perhaps on the lining). The HSE Office conducted an investigation to determine the exact causes of the accident.