False-Positive
A term used by investigators to describe a photo, video, audio recording, or meter reading that seems to show paranormal activity, but in fact is caused by something natural is called a False-Positive.
About 8 years ago when I started investigating claims of paranormal activity, any picture that I took that had something in it that I couldn't explain became something of a paranormal nature. I didn't know how to tell dust or flashback from a real orb. I couldn't tell the difference between smoke or breath in cold weather and ectoplasmic mist or a camera strap from a vortex. Whispering on my audio tape was true EVP to me and any EMF meter spike or temperature drop indicated the presence of a spirit. Below are a few simple guidelines to help distinguish what may be paranormal evidence and what is definitely not. Of course, these are guidelines used by Metroplex Paranormal Investigations. There are no paranormal experts regardless of what you may read. There aren't any accredited schools giving out degrees in parapsychology in the United States. If someone tells you that they are a parapsychologist, they've probably taken an online course offered by other ghost hunters.
Photography and Video
When using your digital or 35 mm camera, always take at least two pictures of the same area. This will help you to rule out something that may look like an orb.
Dust will hang in the air and will be in both pictures. In other words, spirit orbs travel quickly and it's difficult to capture them. If you have an orb in one picture and not in the other, you may have something. Does it leave a contrail (or tail)? A contrail happens when an object is moving faster than your shutter speed or faster than your camera can record it. On video, look at the speed and flight path of the "orb". Does it seem to have an idea of where it's going or is it just floating about and remaining on screen? Another note on dust - it's static and will cling near or to other dust particles. If your photo is full of orbs, it's most likely dust. Dust also clings to your camera lens (and video camera lens), so make sure to clean the lens with an anti-static wipe before using.
When you are near a reflective surface, the flash from your camera can reflect off that surface and flash back to your camera lens. Your camera lens is round, an orb is round. Your picture is going to be the flashback, not a spirit orb.
Reflective surfaces include picture frames, light fixtures, highly polished wood surfaces, windows, glossy headstones. If you can see yourself in the surface, it's reflective.
Moisture falling, like rain and snow, can also give you false-positive orbs.
Ectoplasmic mist looks a lot like cigarette smoke or breath on a cold day. It's common sense not to smoke near an investigation area. Also, hold your breath when it's cold outside as you take your picture. Fog from a water source, be it a nearby lake or dew on the grass can also give you false-positive evidence.
The most common pictures of a vortex that I have seen posted on the internet are actually those of a camera strap. The braiding of the strap should tell you that it's not a vortex. The flash bleaches out the strap and the strap is usually on the same side as the shutter release. A vortex is supposed to be a column of energy and is believed to be a doorway between the physical world and the spirit world. A column is vertical (up and down) not horizontal (side to side). It does not loop around and go back to the same place it started.
Keep in mind that hair can also fall in front of the camera lens and the flash will bleach it out and give you false-positive evidence.
EMF Meters
An Electromagnetic Field Detector allows you to detect and follow energy sources. It detects changes in electromagnetic fields and moving low level EMF fields that don't have a source.
Some things that will disrupt the fields are: appliances, a/c heating units, wall sockets and switches, ceiling fans and even taking pictures near the meter. Make sure you take initial field readings and are aware of energy sources before your investigation starts. You are looking for EMF readings between 2.0 and 7.0.
Thermometers
We use non-contact infrared thermometers and regular digital thermometers. We use the digital thermometers to get a base room temperature before we start our investigation. We then use the non contact infrared thermometers during the investigation to scan and record temperatures of a large area. Whatever the end of the beam hits, is what the temperature is being recorded on. Theoretically, an entity will pass through the beam of this thermometer causing the temperature to drop. We are looking for temperature drops of at least 15 degrees which may indicate the presence of a spirit. Some things to look for that may cause fluctuations in temperature: air leaks at windows and doors and the window glass itself, stovetops and ovens that have recently been used, temperatures around air conditioning vents.
EVP
Electronic Voice Phenomena (or EVP) is literally the voices of the dead that are only heard when a recording is played back, not as it is being recorded.
When recording EVP, make sure everyone speaks in a normal tone of voice instead of whispering unless you demand total silence. We have found both ways work and sometimes a spirit will join in the conversation or comment on what we are doing. Again, be aware of your surroundings. Take note of dogs barking, birds chirping, traffic noise, etc..
There is also the term (coined by GHOULI in Oklahoma) SSP or Spontaneous Sound Phenomena. This would cover any unexplained loud bangs or other odd sounds that may turn up in your recording. We have a recording that sounds like someone is playing a ping-pong match where there is no ping-pong table. GHOULI also has an EVP classification system. While it's too long to go into here, you can visit their site for the information (http://www.ghouli.org).
Ask short, direct questions and maybe you'll get a short, direct answer.
Another possibility for EVP interference is radio waves. Although our recorders are not meant to pick up radio waves, the possibility exists.
The best advice I can give you when examining your evidence is to use common sense. If you consider yourself a paranormal investigator instead of just a "ghost hunter" then you need to really investigate a location and view your evidence with a critical eye.
This is one of the best reasons to have a paranormal investigation group. No one person can think of everything, and it really helps to have a great team of people working beside you like I do.