Theatrical smoke and fog, also known as special effect smoke, fog or haze, is a category of atmospheric effects used in the entertainment industry. The use of fogs can be found throughout motion picture and television productions, live theatre, concerts, at nightclubs and raves, amusement and theme parks and even in video arcades and similar venues. These atmospheric effects are used for creating special effects, to make lighting and lighting effects visible, and to create a specific sense of mood or atmosphere. Recently smaller, cheaper fog machines have become available to the general public, and fog effects are becoming more common in residential applications, from small house parties to Halloween and Christmas.
Theatrical fog and theatrical fog machines are also becoming more prevalent in industrial applications outside of the entertainment industry, due to their ease of use, inherent portability and ruggedness. Common popular applications for theatrical fog include environmental testing (such as HVAC inspections) as well as emergency personnel and disaster response training exercises.
Militaries have historically used smoke and fog to mask troop movements in training and combat, the techniques of which are technologically similar to those used in theatre and film.
Health harms can be caused by short- and long-term exposure to artificial fogs. Some types of fog are less healthy than others. Handling the generating equipment also has health risks.