An alternate system runs on the fog or good mist Greenhouse Exhaust Fan injected into 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 essential components are shown in Fig. 1. A two-stage system managed by a two- stage thermostat allows more water to be applied on excessively warm, shiny days. Temperature settings should be 5-10°F apart.

Algae growth in the pads may become a problem that will decrease the effectiveness of the machine and lead to accelerated deterioration of the pads. The addition of an algaecide to the drinking water supply can help in control.

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

Water for the pads should be clean and lower 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 each and every minute per linear foot of pad system ought to be provided to guarantee adequate wetting.

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