An alternate system runs on the fog or good 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 using a ruthless piston pump and fog nozzles. The essential components are demonstrated in Fig. 1. A two-stage system managed by a two- stage thermostat allows more water to be employed on excessively warm, bright days. Temperature settings ought to be 5-10°F apart.
Algae development in the pads can become a problem that may decrease 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 water areas, to add a wetting agent to the water to obtain additional uniform wetting of the pads. A commercial materials or liquid home 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 prevent 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 program ought to be provided to guarantee adequate wetting.
In the most typical cooling system (fan and pad), the fans draw air through wet pads that prolong the length of one endwall or sidewall. Aspen and coated cellulose are common pad materials that usually have life of one to three years. Approximately one square foot of pad are is needed for 20 square foot of floor area.
Greenhouse Exhaust Fan information and misconceptions.
