Detection of mercury vapour

After some research in my chemistry books, I settled on cuprous iodide / silver iodide paste mixed with precipitated sulphur as a possible reagent. The reagent was made by double decomposition of silver nitrate and copper sulphate solutions added to a solution of potassium iodide. The resulting yellow paste was painted onto filter paper and allowed to dry. On exposing to mercury vapour in a glass vial, the exposed area turned a satisfying but not very visible light amber colour. I doubt that it would detect the vapour from the mercury spill which occurred some years ago in the kiln room...