An alternate system uses a fog or fine mist injected in to the intake air stream. Although a number of commercial systems are available, growers can assemble and set up their own system using a high pressure piston pump and fog nozzles. The essential components are proven 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 ought to be 5-10°F apart.

Algae development in the pads can become a problem that may decrease 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 include a wetting agent to the drinking water to obtain additional uniform wetting of the pads. A commercial material or liquid household detergent at the price of 2 tablespoons per 100 gallons can be used.

Drinking water for the pads ought to 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 each and every minute per linear foot of pad program ought to be provided to ensure adequate wetting.

In the most typical cooling system (fan and pad), the fans draw air through wet pads that lengthen the length of one endwall or sidewall. Aspen and covered cellulose are Greenhouse Exhaust Fan normal pad materials that always have life of 1 to three years. Approximately one square foot of pad are is needed for 20 square ft of floor area.