An alternate system runs on the fog or great mist injected into the intake air stream. Although a number of commercial systems can be found, growers can assemble and set up their own system utilizing a high pressure piston pump and fog nozzles. The basic components are proven in Fig. 1. A two-stage system managed by a two- stage thermostat allows more water to be employed on excessively warm, shiny days. Temperature settings should be 5-10°F apart.
Algae development in the pads can become a Greenhouse Auto Vent problem which will reduce the effectiveness of the machine and lead to accelerated deterioration of the pads. The addition of an algaecide to the water supply will help in control.
It really is desirable, especially in hard water areas, to add a wetting agent to the drinking water to obtain more uniform wetting of the pads. A commercial material or liquid household detergent at the rate of 2 tablespoons per 100 gallons may be used.
Water for the pads should be clean and low in mineral content 
to avoid clogging and coating of the pads. A pump, pipes and gutters are used to recirculate the water. A flow rate 113 gallon each and every minute per linear foot of pad system ought to be provided to make sure adequate wetting.
In the most common cooling system (fan and pad), the fans draw air through wet pads that lengthen the length of 1 endwall or sidewall. Aspen and coated cellulose are common pad materials that always have life of one to three years. Approximately one square foot of pad are is necessary for 20 square ft of floor area.