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 ruthless piston pump and fog nozzles. The basic components are demonstrated in Fig. 1. A two-stage system controlled by a two- stage thermostat allows more water to be applied on excessively warm, shiny days. Temperature settings ought to be 5-10°F apart.
Algae growth in the pads can become a problem which will reduce the effectiveness of the system and lead to accelerated deterioration of the pads. 
The addition of an algaecide to the water supply will help in control.
It is desirable, especially in hard water areas, to add a wetting agent to the drinking water to obtain more uniform wetting of the pads. A commercial materials or liquid home detergent at the price of 2 tablespoons per 100 gallons can be used.
Drinking 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 each and every minute per linear foot of pad system should be provided to make certain adequate wetting.
In the most Greenhouse Exhaust Fan typical coolant 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 usually have life of 1 to 3 years. Approximately one square foot of pad are is needed for 20 square foot of floor area.