An alternate system uses a fog or fine mist injected into the intake air stream. Although many commercial systems are available, growers can assemble and install their own system using a high pressure piston pump and fog nozzles. The essential components are proven in Fig. 1. A Greenhouse Exhaust Fan two-stage system controlled by a two- stage thermostat enables 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 problem that may reduce the 
effectiveness of the system and lead to accelerated deterioration of the pads. The addition of an algaecide to the drinking water supply can help in control.
It is desirable, especially in hard drinking water areas, to include a wetting agent to the water to obtain more uniform wetting of the pads. A commercial material or liquid household detergent at the price of 2 tablespoons per 100 gallons can be used.
Drinking water for the pads ought to be clean and lower in mineral content to prevent clogging and coating of the pads. A pump, pipes and gutters are used to recirculate the drinking water. A flow rate 113 gallon each and every minute per linear foot of pad system should be provided to make certain adequate wetting.
In the most typical coolant system (fan and pad), the fans draw air through wet pads that extend the length of one endwall or sidewall. Aspen and coated cellulose are normal pad materials that always have life of 1 to 3 years. Approximately one sq . foot of pad are is needed for 20 square feet of floor area.