The steam produced upon flashing after postulated pipe rupture accident in the containment of a nuclear power plant (NPP) is routed to the vapour suppression pool via the vent system. Subsequently, the steam-air mixture comes in direct contact with sub-cooled water in the pool resulting in direct contact condensation (DCC) of steam in the suppression pool. The condensation of steam in the pool could be sustained at high incoming flow rates. However, when the steam flow rate reduces because of pressure decrease in the containment, steady condensation cannot be sustained. In this case, the energy exchange between the steam bubble and subcooled water causes the bubble to collapse, causing pressure oscillations. The resulting intermittent unsteady condensation phenomenon is called "steam chugging". It is known that chugging is dominated by several important geometrical and process parameters such as upstream pressure, steam mass flow rate, sub-cooling of pool water, vent system configuration (submergence depth, orifice, and vent pipe size), presence of non-condensable gases in steam etc. To bring out the influence of key variables, a geometry consisting of a drywell and wet-well connected by a vent system is considered. The numerical model is applied to capture the effect of important variables on steam chugging phenomena. The discussions in this paper are limited to explaining the influence of individual parameters by comparing them with a base case value.