With all ghost hunting shows, there are only two possible outcomes; either a ghost is found, or not (so really one possible outcome). Producers have to prepare for either scenario.
TV shows where a group of people search for ghosts are freaking everywhere. Despite there being a slightly different twist to each one, and them being aired on multiple networks, they all follow roughly the same format.
The typical show of this variety "casts" a group of "trained" "professionals" to "investigate" locations that have "reputations" for being "haunted".1 These investigations are recorded mostly on hand held cameras operated by the cast members, cut and edited down to an hour long episode, then aired on any network that is somewhat science based.
1 Possibly the most sarcastic quotes that have ever been required in one sentance. And yes, they are required
Despite how scary some of the locations appear to be, and no matter how shaky the hand held cam is, these shows all share on common flaw..... they never, ever, ever discover any ghosts, and every single viewer knows that before they even turn on the show.
The actual discovery of paranormal activity, or life after death, or anything of the like would be considered the most incredible discovery in the history of mankind. We would finally know a little of what happens after death. Religious beliefs would be proven right or wrong. The Bible, the Quran, etc might all have to be re-written. It would be such a monumental shift in what people believe and the way we live that every single person on Earth's life would change forever.
So, since this would be such an important event, we now have twenty different shows that feature a bunch of assholes walking around an old prison scaring themselves for an hour, then at the end declaring their tests to be inconclusive. If they were to really discover ghosts it would not be revealed at the end of a show on TLC or whatever channel these are on. Do they expect viewers to really believe that they would air an earth changing event like the actual discovery of an afterlife as just a normal show airing after a Stargate rerun?
So basically the flaw of these shows, and the reason they will not be around in two years, is that we already know the outcome of every show, yet they are still presented as being suspenseful, and that shit gets old real quick. We are probably about a season away from one of the shows introducing a long lost little brother, or a cast member recieving magical powers, or some other cliche that shows call on when ratings start to dip.
A typical cast of a ghost hunting show consists of one or two people that have some sort of vague science background, a good-looking person, an everyman type, and someone that scares easily (sorta like how Survivor is cast). These cast members utilize a variety of ghost hunting techniques and equipment to freak themselves out when the tempurature changes, or an arbitrary reading is either higher or lower than they would expect. Some of this equipment includes:
Electomagnetic Field Scanner
The name of this device gives away what it does so let's skip the explanation. The reason it is believed that the disturbance of an electromagnetic field might indicate the presence of the paranormal is based on a study by Michael Persinger, Professor of Psychology at Laurentian University, Ontario, Canada. Professor Persinger found that when subjects were exposed to magnetic pulses they often described feeling a presence near them. So those that hunt ghosts, being absolute professionals and not, we repeat, NOT, a bunch of seven year olds, take that information and assume that the inverse must also be true and the presence of an electromagnetic field means the boogeyman is here.
The theory here is that when a ghost appears, the temperature in the area will drastically drop or elevate. The basis for this theory is a.... um.... well.... it happened in The Sixth Sense?
It is believed that changes in radiation levels could indicate the existence of ghosts. This belief stems from, really nothing. At this point they must just working under the assumption that there is a chance that anything that can't be detected by the human eye could indicate the presence of the supernatural. On future episodes, the existence of dust mites and air may serve as indicators of ghosts.