An alternate system runs on the fog or fine mist injected into the intake air stream. Although several commercial systems can be found, growers can assemble and install their own system utilizing a ruthless piston pump and fog nozzles. The essential 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, bright days. Temperature settings ought to be 5-10°F apart.

Algae growth in the pads can become a problem which will reduce the effectiveness of the system and result in accelerated deterioration of the pads. The addition of an algaecide to the drinking water supply will help in control.

It really is desirable, especially in hard water areas, to add a wetting agent to the drinking water to obtain more uniform wetting of the pads. A commercial material or liquid household detergent at the rate of 2 tablespoons per 100 gallons can be used.

Water for the pads should be clean and low in mineral content to Greenhouse Exhaust Fan prevent clogging and coating of the pads. A pump, pipes and gutters are accustomed to recirculate the water. A flow rate 113 gallon per minute per linear foot of pad system should be provided to make sure adequate wetting.

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