Interestingly, investigators who put their hands into these hot spots often report a cold sensation.
    Color thermal imagers are still out of the reach of most ghosthunters, with prices in the $50,000 range.  Most often, television shows such as Sightings rent or borrow the imagers to film a field investigation.  Less expensive ($8,000) black-and-white imagers, developed for police and firefighting applications, are not sensitive enough for paranormal investigations.

Night Vision Devices
    The military developed light-intensifying lenses for night surveillance.  With their stark, green-glowing image field, these units will not work in absolute darkness but will electronically amplify minute levels of available light (such as moonlight, starlight or IR emitters) to provide a functional image where unaided eyesight or photography would be useless.  This allows late-night surveillance in a haunted house without having to turn the lights on.  Some ghostly phenomena are reported to be more active at night, and the use of artificial lighting might inhibit a paranormal event.  Night vision devices have also allowed investigators to film misty or vaporous manifestations that would have appeared washed-out or invisible under illuminated conditions.

Thermometers

    Short of using expensive thermal imaging units, the best way to document a paranormal cold spot is with a rapid-reading electronic thermometer. (Forget the old mercury-filled tubes).  The best type will give a constant background reading of the room and have an external probe that can be directly inserted into a cold spot.  Many units will record and store data continuously, and some can be programmed to sound an alarm if the temperature drops or rises beyond set parameters.

A Definitive Answer?
    While we have yet to come up with a piece of equipment that can prove the existence of a ghost (just what is a ghost?), we can detect and document the unexplained environmental changes that occur in haunted locations.  We have made more discoveries and compiled more evidence in the past 16 years than in the entire history of organized ghost research.  As science and technology continue to advance, it is not unreasonable to hope that within our lifetime we will be able to define, categorize, and positively establish the existence of ghosts.