Most cyanide contaminated sites are due to the historic use of the land for gas production with cyanide present in both free and complexed forms. In order to remove impurities such as hydrogen sulphide, carbon dioxide and hydrogen cyanide from the generated gas, it was passed through ferric oxide forming ‘blue billy’. 'Spent' oxide was then often disposed of on-site.

Cyanides can also be found in old print works where the deep blue pigment Prussian blue was used in the making of blueprints. It is derived from iron-cyanide complexes (hence the name cyanide, from cyan - a shade of blue).

QROS offer a rapid on-site technique that is able to quantify soluble cyanide in approximately 20 minutes with detection limits down to 1 ppm