These devices are commonly sold as ghost hunting gear, but there is no logical or scientific reason to use this equipment when looking for the paranormal. EMF detectors measure electromagnetic fields, not ghosts; infrared cameras reveal the infrared spectrum, not ghosts. There is no evidence that ghosts have anything to do with electromagnetic fields, infrared images, ions, temperature drops, etc.
4) Electronic Voice Phenomena
Most ghost hunters, including the "Ghost Hunters" team, use handheld voice recorders in an attempt to capture a supposed ghost voice, or EVP. Often an investigator will hold the recorder while standing in the middle of a room and addressing the supposed spirit, or while walking around. He will later go back and review the recordings at high volume, listening for any faint murmurs, sounds or noises, which may be interpreted as ghost voices. For example, a ghost hunter may ask out-loud, "If there's a spirit here, what's your name?"
Often the investigator will get no answer at all; other times, if the ghost hunters wait long enough they'll hear some random sound that could be interpreted as a faint, mumbled name: "Mary." (Or maybe Terry, Kerry, Larry or Barry - never mind the fact that, as disembodied spirits, ghosts presumably do not have vocal cords, a tongue or a mouth that would allow them to speak.)