An alternate system runs on the fog or fine mist injected into the intake air stream. Although a number of commercial systems are available, growers can assemble and install their own system using a ruthless piston pump and fog nozzles. The basic components are proven in Fig. 1. A two-stage system managed by a two- stage thermostat allows more water to be applied on excessively warm, shiny days. Temperature settings should be 5-10°F apart.

Algae development in the pads may become a problem that will decrease the effectiveness of the machine and lead to accelerated deterioration of the pads. The addition of an algaecide to the Greenhouse Auto Vent drinking water supply can help in control.

It 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 materials or liquid home detergent at the price of 2 tablespoons per 100 gallons can 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 used 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 sure adequate wetting.

In the most common coolant 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 always have life of one to three years. Approximately one sq . foot of pad are is needed for 20 square feet of floor area.