Sirius is a 3 GeV 4 th generation light source under construction by the Brazilian Synchrotron Light Laboratory (LNLS). Sirius will have a low emittance storage ring, 0.28 nm.rad, based on 20 cells of a highly compact lattice – 5 bend achromat (5BA). This lattice concept leaves very little space for components and therefore requires narrow vacuum chambers with tight mechanical tolerances. Most of the storage ring vacuum chambers will be made of oxygen-free silver bearing (OFS) copper and have a circular cross section with inner diameter of 24 mm and a wall thickness of 1 mm. Unused synchrotron radiation will be distributed along the water cooled walls of the chambers. Due to the small conductance of the chambers, vacuum pumping will be based on distributed concept and then non-evaporable getter (NEG) coating will be extensively used, with more than 95% of the chambers being coated. In this paper, we present an overview of the storage ring vacuum system and the fabrication approach for some components.