An alternate Greenhouse Auto Vent system uses a fog or fine mist injected into the intake air stream. Although many 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 
shown 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 can become a problem that may decrease the effectiveness of the machine and result in accelerated deterioration of the pads. The addition of an algaecide to the water supply will help in control.
It is desirable, especially in hard water areas, to add a wetting agent to the 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 should be clean and low in mineral content to prevent 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 program ought to be provided to ensure adequate wetting.
In the most typical coolant system (fan and pad), the fans draw air through wet pads that prolong the length of 1 endwall or sidewall. Aspen and covered cellulose are normal pad materials that usually have life of 1 to three years. Approximately one square foot of pad are is necessary for 20 square ft of floor area.