Fog sensor

Does anyone have a schematic for a fog sensor, or know where i can buy one (cheap stuff to be used onshore)?
To be used as a trigger to disable infrared optical beam smoke when it's foggy.
So it needs relay output and pref run on 24V dc.

Nephelometers measure the light scattered in a forward direction by fog particles and are the most widely used and cost-effective fog sensors. They provide accurate fog density measurement in a selectable output format (visibility in distance units or voltage proportional to fog density). These sensors have low maintenance requirements and are designed with roadside highway use in mind; they are small and lightweight and their light emitters and detectors are contained within their housing, eliminating the need for external lenses and windows.

That's well and good, there are plenty of places more expensive than your think.
Though all things are semiconductor materials. so you may visit or gathered some idea about semiconductor materials.
I’m not recommending but perhaps you could check out this "materials(materials)":http://actpcb.com/Base-Material for your consideration

Thanks!!!!!

Thank you for the answer.