A method for operating an air handling apparatus of a heating, ventilation, and air conditioning system associated with first and second thermal zones of an enclosed space having a plurality of zones, wherein the air handling apparatus includes an air handling unit or a rooftop unit, said air handling unit or rooftop unit including an outside air flow actuator, a variable air volume device associated with the first zone and a variable air volume device associated with the second zone wherein each variable air volume device includes a VAV air flow actuator and a VAV air temperature control actuator, the method comprising: opening the outside air flow actuator to enable breathing air flow in a supply duct during a high outdoor air time period wherein the supply duct conveys breathing air to the first and second zones and wherein the first zone includes a first number of occupants and the second zone includes a second number of occupants that is less than the first number of occupants; closing the outside air flow actuator to enable conditioning air flow into the supply duct during a low outdoor air time period wherein the supply duct conveys conditioning air to the first and second zones; operating the air handling unit or rooftop unit and VAV air flow actuators to provide a desired amount of breathing air to the first zone suitable for the first number of occupants and breathing air to the second zone suitable for the second number of occupants, wherein the air handling unit or rooftop unit and VAV air flow actuators are operated during the high and low outdoor air time periods (108, 112); and operating the VAV air temperature control actuators to provide temperature controlled air to the first zone having a suitable temperature for the first number of occupants and temperature controlled air to the second zone having a suitable temperature for the second number of occupants, wherein the VAV air temperature control actuators are operated during the high and low outdoor air time periods (108, 112) and wherein the outside air flow actuator, the VAV air flow actuators and the VAV air temperature control actuators are controlled using pulse width modulated signals to cycle the high and low outdoor air time periods (108, 112), and calculating a carbon dioxide level for an associated zone based on a combined carbon dioxide level measurement within a return duct for the first and second zones and the number of occupants in the associated zone, wherein the number of occupants in the first zone and the number of occupants in the second zone is determined by a calendaring application or web portal. opening the outside air flow actuator to enable breathing air flow in a supply duct during a high outdoor air time period wherein the supply duct conveys breathing air to the first and second zones and wherein the first zone includes a first number of occupants and the second zone includes a second number of occupants that is less than the first number of occupants; closing the outside air flow actuator to enable conditioning air flow into the supply duct during a low outdoor air time period wherein the supply duct conveys conditioning air to the first and second zones; operating the air handling unit or rooftop unit and VAV air flow actuators to provide a desired amount of breathing air to the first zone suitable for the first number of occupants and breathing air to the second zone suitable for the second number of occupants, wherein the air handling unit or rooftop unit and VAV air flow actuators are operated during the high and low outdoor air time periods (108, 112); and operating the VAV air temperature control actuators to provide temperature controlled air to the first zone having a suitable temperature for the first number of occupants and temperature controlled air to the second zone having a suitable temperature for the second number of occupants, wherein the VAV air temperature control actuators are operated during the high and low outdoor air time periods (108, 112) and wherein the outside air flow actuator, the VAV air flow actuators and the VAV air temperature control actuators are controlled using pulse width modulated signals to cycle the high and low outdoor air time periods (108, 112), and calculating a carbon dioxide level for an associated zone based on a combined carbon dioxide level measurement within a return duct for the first and second zones and the number of occupants in the associated zone, wherein the number of occupants in the first zone and the number of occupants in the second zone is determined by a calendaring application or web portal.