In theory when a spirit/ghost starts to manifest, it will draw in heat energy around the area, causing either a cold spot or a hot spot. A cold spot would form because the heat energy is being sucked out of the air, causing the air around the entity to be cold. A hot spot would form because the heat energy is being sucked out of the air and confined to a specific area, causing a hot spot.
Cold Spot Hot Spot
The equipment that we use to test these theories are as follows:
IR (Infrared) Surface Thermometers
Ambient Air Temperature Thermometers