An alternate system uses a fog or great mist injected into the intake air stream. Although a number of commercial systems can be found, growers can assemble and install their own system utilizing a high pressure piston pump and fog nozzles. The essential components are demonstrated in Fig. 1. A two-stage system controlled by a two- stage thermostat allows more water to be employed on excessively warm, bright days. Temperature settings should be 5-10°F apart.
Algae growth in the pads may become a problem which will reduce the effectiveness of the system and result in accelerated deterioration of the pads. The addition of an algaecide to the water supply can help in control.
It really is desirable, especially in hard drinking 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 can be used.
Drinking water for the pads ought to be clean and lower 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 per minute per linear foot of pad system should be provided to make sure adequate wetting.
In the most common coolant system (fan and pad), the fans draw air through wet pads that expand 
the length of 1 endwall or sidewall. Aspen and coated cellulose are normal pad materials that always have life of 1 to 3 years. Approximately one square foot of pad are is necessary for 20 square ft of floor area.
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