An alternate system runs on the fog or fine mist injected in to the intake air stream. Although many Greenhouse Exhaust Fan commercial systems can be found, growers can assemble and install their own system using 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, shiny days. Temperature settings ought to be 5-10°F apart.
Algae growth in the pads may become a problem that will reduce the effectiveness of the machine and result in accelerated deterioration of the pads. The addition of an algaecide to the drinking water supply will help in control.
It really 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 home detergent at the price of 2 tablespoons per 100 gallons may 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 accustomed 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 certain adequate wetting.
In the most typical cooling 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 three years. Approximately one square foot of pad are is needed for 20 square ft of floor area.