Mechanical systems not only ventilate indoor spaces, but they also heat, cool, humidify and dehumidify. Forced ventilation systems powered by electric motors create pressure difference to move air in the desired direction and keep air quality at an acceptable level. In order to meet fan requirements, utilities and OEMs can specify motors to be used in a ventilation system. Specifications feature required input parameters such as load inertia when used with DOL /Star Delta/Reduced Voltage fixed frequency supply system. Another energy-saving factor coming into common use is variable frequency drives, which makes selection of the motor easier. With a variable frequency drive, the starting time does not affect the size of the motor. Any HVAC motor must deliver high-class, reliable performance to ensure the performance of the fan and consume less energy and reduce carbon dioxide emissions.