*Poorly grounded or unshielded structural wiring

*Microwave ovens in use

*Dimmer switches

*Cellular phones in use

*FM, FRS, GRS and Citizen Band radio transceivers in use

*Air conditioning and Power system/stations

*Television screens, Plasma screens, LCD Screens

*Computers

*Power lines within 100 yards, especially HIGH VOLTAGE (tension) towers and transformers

*Fuse boxes

*Stored static energy (walking over any carpeting or rugs)

*Fluorescent lighting (the ballast capacitors, not the bulbs)

*Electrical appliances over 5 years old

*Battery operated wrist watches

*Pagers (activated)

*Excessive movement within the survey area

*Overcrowding within the survey area

*Poorly insulated doorframes and windows

*Access holes for wiring left uninsulated

*Bulkheads

*Forced air Heating/AC systems (within 10' of registers)

*Ajar windows and or doors

*Electronics cooling fans

*House settling (15 years old or less)

*Natural underground water systems

*Structural heating and cooling

*Use of off balance motorized major appliances within 12 hours in the general suspect area before the survey

*Heating or AC systems in use

*In use fans and natural drafts

*Dusty rooms

*Animal and or insect infestation

This is by no means a complete list of things that can and do occasionally lead paranormal investigators astray, but they are the most common that you'll run into in the field. Remember that a good investigator is one that remains a skeptic until all possible natural causes are eliminated.