Mists that roll in at dusk can be both calming and eerie. But paranormal mists always send chills up your spine. As, usual, many theories exist to explain mists in the paranormal context. There are many things that can cause mists and most of them are completely natural. Fog is one of them.
Fog forms when there is difference of approximately 5 degrees between air temperature and dew point. Fog is essentially a cloud that forms next to the earth's surface. Another key element to the formation of fog is the presence of water vapor in the air near the ground. A key measurement that must be made by paranormal researchers is the relative humidity. A combination of measurements can be used to determine whether fog formation is possible. Dew point, barometric pressure, humidity, and temperature all play a role in the formation of fog.

If the relative humidity is over 90% and the dew point rises above the temperature, a type of fog can form which is known as flash fog. In these conditions, the only thing that it takes for fog to form in a matter of seconds is to breathe in the room. The water particles in your breathe can provide enough nuclei for the water vapor to condense upon and surround you with a "mysterious" mist that "comes out of thin air".
Breath can form a mist as well if conditions are right. Anyone who has lived in a place that gets cold has seen their breath. So, when it's chilly outside and you can see your breath; do not forget to hold your breath before snapping that picture. If you can't, your evidence will be contaminated.

When on an investigation, it might be best to ensure that no one smokes, especially if they are taking pictures. A majority of the "mist" pictures you see on the Internet are nothing more than cigarette smoke. We have seen people who smoke as if it is second nature who are completely unaware they are contaminating their own evidence.

Mists of a paranormal nature are extremely rare. Most often they present in conditions in which they could be explained away as natural phenomena. Regular mists or fogs can seem to undulate as air currents buffet them around. Paranormal mists which can be considered as evidence move in a manner that contradicts those movements seen in regular mist. Paranormal mists might be a dark color or seem to have streamers (similar to smoke). They may also appear to grow or shrink. A mist that grows then dissipates is probably just regular mist.

So, the identification of a mist as being paranormal can only begin to be undertaken AFTER all scientific measurements have been taken. Humidity, barometric pressure, dew point and temperature must be recorded. if they indicate the possibility or likelihood of fog, mist evidence must be considered invalid. There are circumstances that might negate invalidating the mist due to natural causes. And we would all like to see evidence so profound as to negate natural explanation.

Dust plays a major part in the orb phenomenon. It also plays an equally major role in the mist phenomenon. We have seen so many "mist" videos and photos that can be explained as someone stirring up dust and recording a draft blowing the dust around.

As you can see, there are a great many natural explanations for mists. This page has only touched the surface. Unfortunately, the burden of proof lies with the researcher. So it is imperative that we account for all natural causes before leaning toward a paranormal explanation.