An alternate system uses a fog or great mist injected into the intake air stream. Although several commercial systems are available, growers can assemble and install their own system utilizing a ruthless piston pump and fog nozzles. The basic components are shown in Fig. 1. A two-stage system controlled by a two- stage thermostat enables more water to be applied on excessively warm, bright days. Temperature 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 drinking 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 material or liquid household detergent at the price of 2 tablespoons per 100 gallons can be used.
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 drinking water. 
A flow rate 113 gallon each and every minute per linear foot of pad system should be provided to assure adequate wetting.
In the most common cooling system (fan and pad), the fans draw air through wet pads that extend the length of 1 endwall or sidewall. Aspen and coated cellulose are common pad materials that Greenhouse Exhaust Fan always have life of one to three years. Approximately one sq . foot of pad are is necessary for 20 square foot of floor area.