Unusual cold spots are best measured by ambient thermometers and thermal imagers such as Forward Looking Infra-Red (FLIR). When cold spots are detected, unusual phenomena usually occur, such as EVPs, strange sounds, objects moving, or creepy feelings.
Digital Infrared or laser thermometers are not recommended because they only measure the temperature of an object or wall you are pointing at via the invisible beam of light. By contrast, ambient thermometers sample the air around or in front of you, which is where you are sensing the coldness.
Not to completely throw out the IR/laser thermometers - maybe you want to get a reading on that chair you suspect a ghost is sitting in?
I've done a little more research on how infrared detection works (actually I was trying to figure out if my trap camera was worth packing around) and I am even more skeptical of the FLIR as a paranormal investigative tool than before.
My NEW understanding of the FLIR (and infrared motion detection devices) is that they are passive instruments...no infrared light or beam is projected unlike a thermometer or IR camera. They "see" and record infrared just as a camera sees visible light.
Everything that has a temperature, hot or cold, has an infrared "signature". Basically infrared is a product of heat (or vice versa...still fuzzy on that).
If a manifestation actually produces a hot or cold spot then THAT can be measured as the FLIR can "see" air temperature in some cases. However, since we still don't have a handle on that process (i.e. what if the manifestation is "room temperature"...no one has proved to me that it doesn't happen) we can't rely on the FLIR to give us accurate or usuable information in many cases.
That is not to say it isn't another useful tool in the box. It just means that the occasional dark or light spot on a wall CANNOT be assumed to be paranormal just because we are not sure what caused it. At this point I am thinking FLIR data would only be truly useful as a correlation to another device (i.e. you see an unexplained shadow on your camera and the FLIR shows it has an infrared signature). In other words walking around recording with a FLIR is a waste of time UNLESS you have an IR or FS camera in the other hand.
Basically it means that I have decided that Ghost Hunters spends WAY too much time investigating with one just because it looks really cool.
Motion detectors are another passive infrared device. The do NOT actually detect motion. They react to changes/movement in the infrared spectrum. Their weakness is that they measure a fairly narrow range of the spectrum since they are calibrated to look for LIVE movement. A "cold spot" probably would not trip most of them.
Feel free to correct me if I have misunderstood how they work. Wouldn't be the first time I was wrong.
