An alternate system uses a fog or good mist injected into the intake air stream. Although many commercial systems are available, growers can Greenhouse Exhaust Fan assemble and set up their own system using a ruthless piston pump and fog nozzles. The basic components are shown in Fig. 1. A two-stage system controlled by a two- stage thermostat allows more water to be employed on excessively warm, bright days. Temperature settings ought to be 5-10°F apart.

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

Water for the pads ought to 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 water. A flow rate 113 gallon per minute per linear foot of pad system ought to be provided to make sure adequate wetting.

In the most common cooling system (fan and pad), the fans draw air through wet pads that expand the length of 1 endwall or sidewall. Aspen and covered cellulose are common 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.