These devices, often referred to as fog machines or haze machines, create a visible vapor using a mixture of water and glycol or glycerin. This mixture is heated and then rapidly cooled upon release, condensing into a suspension of microscopic water droplets that resemble smoke or fog. Different formulations of the fluid can create varying densities and durations of the effect.
The primary advantage of this technology is its relative safety compared to older methods that used oil-based fluids or dry ice. The water-based fluid is typically non-toxic, non-flammable, and leaves minimal residue, reducing the risk of fire hazards or respiratory irritation. This makes them suitable for a wide range of applications, from theatrical productions and concerts to industrial simulations and safety training. The development of these machines marked a significant improvement in special effects technology, allowing for more controlled and safer atmospheric effects.