a) Central Mechanical Ventilation Including Heating, Cooling and Heat Recovery:
           By recovering the residual heat in the exhaust gas, the fresh air introduced into            the air conditioning is pre-heated which ultimately improves the energy                          efficiency.
       b) Central Mechanical Ventilation with Heating and Cooling:
            Intentional exchange of indoor air and fresh outdoor air at a controlled rate                    using fans.
       c) Local Ventilation (e.g. Window/Wall/Roof Units):
            Packaged unit components are housed in  one cabinet which is directly                          connected to the ventilation system to circulate the air.
       d) Other Local Units (Fan Coil Units):
             
Fan Coil Unit is a simple device with heating and cooling coil to circulate the                air.

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