SF6 gas has been adopted asan alternative of air for insulation technology in modern day industry due to its high dielectric strength and arc quenching properties. In the recent past, electrical substations are employing gas insulation because of its better properties and also lower space requirement. One of the major reasons for the failure of these gas insulated substations (GIS) is the particle contamination. The free metallic contaminating particles move in the gas insulated busducts by the influence of electric field and lead to the breakdown of the unit.The movement of these particles is governed by various factors and is primarily limited by the drag force which is a function of the pressure of the gas medium.The present work aims at investigating the impact of the SF6 gas pressure, inside the earthed metallic enclosures, on the metallic particle movement. Power frequency overvoltages generally employed for normal transmission are considered. Besides, the study is conducted on different dimensions of gas insulated busduct for better relevance.Wire type particles of commonly encountered contamination, aluminium and copper, with length 12mm and radius 0.25mm are considered to be present on the inner surface of the enclosure. The results show that the maximum displacement of the particles in the gas insulated busduct is independent of the gas pressure.