Demand-Controlled Ventilation (DCV) is defined as "a system that provides automatic reduction of outdoor air intake below design rates when the actual occupancy of spaces served by the system is less than design occupancy". Currently, several widely used DCV control approaches are developed based on steady-state equation. This paper presents three transient DCV mathematical models for CO2 concentration calculation. The selected transient model provides a more realistic estimation on CO2 concentration and prediction on the outdoor airflow rate. The transient CO2 concentration is used to calculate the required minimum outdoor air flow rate with three control approaches respectively. In this case study, a typical occupancy profile is selected, and the required minimum outdoor air flow rates based on Standard 62.1 are compared to identify the possibilities of over-ventilating and underventilating. The results show that MTP would provide sufficient ventilation with the least over-ventilation in the particular case study.