Misting systems utilize a spray nozzle designed to produce water droplets that are extremely small about the diameter of a human hair, even as small as 5 millionths of a meter. When water droplets this small hit the surrounding air, they 'flash evaporate' reducing the surrounding temperature as much as 35 degrees Fahrenheit. This scientific principle, known as thermal dynamics.
Water pressure is key in an efficient misting system.
These systems will work only in extreme dry heat. The higher the pressure the more efficient the system operates. Most portables have a operating pressure of 100 psi or lower. Higher pressure systems are available, but are cost prohibitive. A well designed system with pressures of 120 psi and up will work better in environments that are not as extreme or in climates that have higher humidity.