An alternate system runs on the fog or fine mist injected in to the intake air stream. Although a number of commercial systems can be found, growers can assemble and install their own system using a ruthless piston pump and fog nozzles. The essential components are proven in Fig. 1. A two-stage system controlled by a two- stage thermostat allows more water to be applied on excessively warm, bright days. Temperature Greenhouse Exhaust Fan settings should be 5-10°F apart.
Algae development in the pads may 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 drinking water areas, to include a wetting agent to the drinking water to obtain more uniform wetting of the pads. A commercial materials or liquid household detergent at the rate of 2 tablespoons per 100 gallons may be used.
Drinking 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 program ought to be provided to assure adequate wetting.
In the most common cooling system (fan and pad), the fans draw air through wet pads that prolong the length of one endwall or sidewall. Aspen and covered cellulose are normal pad materials that usually have life of 
1 to three years. Approximately one sq . foot of pad are is needed for 20 square ft of floor area.