Cold spot, mist, fog
There is one common thing, that is the temperature is low. I do not do any study on this, one thing I often do is observation and personal encounters. When fog appeared inside a building. Fog appears in isolated place, also fog appear and vanish.
Cold air in a normal outdoor temperature.
A high level spirit usually absorbed the surrounding energy to maintain the energy. This created a area of cold air.
To convince myself I try to trace if there is any paranormal energy, or just the cold air
