An alternate system uses a fog or great mist injected in to the intake air stream. Although several commercial systems are available, growers can assemble and set up their own system utilizing a high pressure piston pump and fog nozzles. The basic components are shown in Fig. 1. A two-stage system managed by a two- stage thermostat allows more water to be employed on excessively warm, shiny days. Temperature settings ought to be 5-10°F apart.

Algae development in the pads can become a problem which will 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 is desirable, especially in hard water areas, to include a wetting agent to the drinking water to obtain more uniform wetting of the pads. A commercial materials or liquid household detergent at the rate of 2 tablespoons per 100 gallons may be used.

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

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