An alternate Greenhouse Exhaust Fan system runs on the fog or good mist injected in to the intake air stream. Although many commercial systems are available, growers can assemble and install their own system using a high pressure piston pump and fog nozzles. The basic components are proven in Fig. 1. A two-stage system managed by a two- stage thermostat allows more water to be employed on excessively warm, bright days. Temperature settings should be 5-10°F apart.
Algae development in the pads can become a problem that 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 is desirable, especially in hard water areas, to include a wetting agent to the water to obtain more uniform wetting of the 
pads. A commercial materials or liquid household detergent at the price of 2 tablespoons per 100 gallons can be used.
Drinking 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 accustomed 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 typical cooling system (fan and pad), the fans draw air 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 one to three years. Approximately one square foot of pad are is necessary for 20 square feet of floor area.