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 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 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 can become a problem that may reduce the effectiveness of the machine 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 water areas, to add a wetting agent to the water to obtain additional uniform wetting of the pads. A commercial materials or liquid home detergent at the price of 2 tablespoons per 100 gallons may 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 assure adequate wetting.

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