Posted By garyh Cyanide is classified as very toxic by inhalation. This can be rapidly fatal. It used to be said that if you could smell it, it smelt like almonds and that was the last thing you ever smelled! Hence, it is unlikely that the smell you can detect is actually cyanide. I would take advice from an organisation that supplies cyanide. Not being funny but you really would need advice from a competent person............. OK if no advice available try and find out what was the cyanide compound used, was it as a gas (unlikely) or, if in an aqueous (water based) solution, what concentration? You could (using suitable PPE) wash with a mild detergent. ON NO ACCOUNT USE ANYTHING ACIDIC such as vinegar............any cyanide could be driven off as gas, and this could be rapidly fatal......... Trouble is, any cyanide, even in very dilute form, is going to end up as a toxic waste. You can't just pour it down the drain. Get some samples taken and anlaysed by a lab (eg a lab used to analysing water / effluent samples would be able to do it). Take it form there; if there is virtually ANY cyanide present, seek professional advice. You could always ask HSE.