An alternate system runs on the fog or great mist injected in to the intake air stream. Although several commercial systems can be found, growers can assemble and install their own system utilizing a high pressure 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 growth in the pads may become a problem that may decrease the effectiveness of the system and result in accelerated deterioration of the pads. The Greenhouse Auto Vent 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 water to obtain more uniform wetting of the pads. A commercial materials or liquid home detergent at the rate of 2 tablespoons per 100 gallons may be used.

Drinking water for the pads should be clean and lower in mineral content to prevent clogging and coating of the pads. A pump, pipes and gutters are used to recirculate the water. A flow rate 113 gallon per minute per linear foot of pad program ought to be provided to make certain adequate wetting.

In the most common cooling system (fan and pad), the fans draw air through wet pads that expand the length of one endwall or sidewall. Aspen and coated cellulose are normal pad materials that always have life of 1 to 3 years. Approximately one sq . foot of pad are is necessary for 20 square foot of floor area.