An alternate Greenhouse Auto Vent 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, shiny days. Temperature settings should be 5-10°F apart.
Algae growth in the pads can become a problem that may decrease the effectiveness of the machine and lead to 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 add a wetting agent to the drinking 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 may be used.
Water for the pads should be clean and lower in mineral content to avoid clogging and coating of the pads. A pump, pipes and gutters are accustomed 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 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 always have life of one to 3 years. Approximately one square foot of pad are is necessary for 20 square foot of floor area.