One of the most commonly seen image types on ghost investigation websites and social media is that of the ghostly mist, where these amorphous shapes can sometimes be seen to form human or other familiar shapes.

While these images can look somewhat spooky, their origins are purely environmental (certainly based on every image of their type I’ve taken in the last thirty years), and the reason folk can see faces and such within the mists falls to pareidolia: usually proven by different people seeing subtly different things. Historically, before the process was known and understood, simple environmental condensation could well explain some of the allegedly paranormal sightings reported – specifics that spring to mind are some of the 16th/17th century descriptions of boggarts and similar, described as amorphous shapes (sometimes described as cloth) rising on roads and in hedgerows in front of travellers.

The process of mists forming in the air is condensation. The air around us can only hold a certain amount of water: if an excess of vapour is added to the air taking the water level above that, then condensation will occur and the surplus water will be ‘expelled’. Another cause of condensation is when the air cools to the point it cannot hold any more water, and again the excess water is expelled. This latter process is called reaching the dew point. The temperature required to reach dew point depends on a number of factors, with the primary factor being the humidity of the environment: simply put, when there is more water naturally in the air the temperature required to hit dew point is higher.

So how does this create so many images misidentified as paranormal? Mostly, it comes down to a lack of knowledge and understanding of how mists form in the air. Outdoors, mists can form spontaneously (and naturally) when the dew point is hit, most commonly when the temperature plummets overnight. Interactions of different air streams can also have an effect – as can the differing temperatures of man-made material, such as warmth held by a path or road triggering a condensation response with air chilling above it.

Underground, such as caves and mines, if you go deep enough temperature remains pretty constant, but airflow through the underground area can alter humidity again triggering a response. 

The same goes with old buildings and similar spaces, especially locations where there is an outdoor interaction: an excellent example is Castle Keep in Newcastle, where the upper Galleries have multiple airflows running from the roof: these can cause rapid changes in temperature and humidity, again triggering a condensation response. 

Now, enter the people taking the photographs. Movement through an area by that person will affect the airflow, and potentially if they stay in an area long enough, their body heat may also affect the temperature of the ambient air. People also produce breath and other vapours laden with moisture, and often when warm breath hits cold air, the vapour excess produced by that person’s breath hitting the air saturates it and causes condensation as explained above: hence the reason a person’s breath often mists in cold air. The temperature needed for this to happy varies due to humidity – with higher ambient humidity resulting sometimes in breath misting in air that doesn’t feel all that cold.

Add this misting breath to the light of a flash and you can get some interesting pictures, especially with the help of a little imagination and pareidolia. So please, next time you see a mist described as proof of the paranormal, please bear in mind its likely a simple environmental reaction, misconstrued or misidentified!