Fog Fluid (also called Fog Juice) is liquid that is used in a fog machine which emits a dense vapor that appears similar to fog or smoke. This artificial fog or smoke is known as theatrical smoke and fog within the entertainment industry. Most fog machines create the fog by either vaporizing a water and glycol-based or glycerine-based fluid or a mineral-oil-based fog via atomization. For glycol-based fogs, the fluid (fog juice) is injected into a heated block, and evaporates quickly. The resulting pressure forces the vapor out of the exit. Upon coming into contact with cool outside air the vapor forms a fog.

Haze Fluid has a substantially longer hang time than conventional fog. While conventional fog may hang in the air for up to 5 minutes, a typical water-based haze can last 1 hour and oil-based haze 6 hours or more, depending on the size of the venue and the amount of ventilation.

Some haze machines use a compressor to atomize a fluid (usually, though not always oil-based), therefore they do not require any warm up time. Other machines use a heater to vaporize the fluid (usually water-based). Most oil-based haze fluids use a mineral oil base, and most water-based fluids use either a glycol or glycerol base.

Hazers produce smaller particles in the air reducing the chance of particle sensor based fire alarm being activated compared to fog machines. The size or particles and effect varies by manufactures and fluid type used.