An alternate system runs on the fog or great mist injected in to the intake air stream. Although several commercial systems are available, growers can assemble and install 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 allows more water to be employed on excessively warm, shiny days. Temperature settings should be 5-10°F apart.

Algae development 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 water supply can help in control.

It really is desirable, especially in hard drinking water areas, to include 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 can be used.

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 per minute per linear foot of pad system should be provided to guarantee adequate wetting.

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