An alternate system uses a fog or good mist injected into the intake air stream. Although a number of commercial systems can be found, growers 
can assemble and set up their own system utilizing a high pressure piston pump and fog nozzles. The basic components are demonstrated in Fig. 1. A two-stage system managed by a two- stage thermostat enables more water to be applied on excessively warm, shiny days. Temperature settings should be 5-10°F apart.
Algae growth in the pads can become a problem that will decrease the effectiveness of the machine and result in accelerated deterioration of the pads. The addition of an algaecide to the drinking water supply will help in control.
It really is desirable, Greenhouse Exhaust Fan especially in hard drinking water areas, to include a wetting agent to the drinking water to obtain additional uniform wetting of the pads. A commercial material 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 accustomed to recirculate the drinking water. A flow rate 113 gallon per minute per linear foot of pad program should be provided to guarantee adequate wetting.
In the most common coolant system (fan and pad), the fans draw air through wet pads that lengthen the length of one endwall or sidewall. Aspen and coated cellulose are normal pad materials that usually have life of one to three years. Approximately one sq . foot of pad are is needed for 20 square feet of floor area.