In this clip, it is very quick, and I noticed you can't see really well unless you focus on the doorway to the left of the hallway.  There are 3 distinct wisps of 'something'.  I reviewed this MANY times and didn't see what could have caused it.  This is the hallway that leads to the room of the spirit that was the focus of the circle that evening.  If you can see it and can determine an explanation, please let me know.  There is NO SMOKING in the building as a precaution due to the fire that was recently suffered there.