According to "Exhaust Fan" exhaust amount selection: This fan, exhaust steam of this effect depends on the fan, exhaust volume, choose this time fans must look at this fan, exhaust and the amount of their own exhaust volume demand agreement, the amount of exhaust ventilation may be a little larger than the demand, the demand is less than the amount of exhaust ventilation effect is less than the design effect, limited installation location, then select as much exhaust volume this fan. According to "Exhaust Fan" electricity consumption choice: This fan is in use, the need to consume energy, the same amount of ventilation, the same size specifications of this fan, the best choice for energy saving such a fan, this fan electricity consumption determined than "Exhaust Fan" by viewing the motor power.