The Spherical gaseous detector (or Spherical Proportional Counter, SPC) is a novel type of particle detector, with a broad range of applications. Its main features include a very low capacitance, a potential low energy threshold independent of the volume, a good energy resolution, robustness and a single detection readout channel. Applications range are from radon emanation gas monitoring, neutron flux and gamma counting and spectroscopy, neutrinos physic, Light WIMP searches and coherent neutrino scattering measurement. Laboratories interested in these various applications share expertise within the NEWS-G (New Experiments With Sphere) Collaboration. NEWS-G_LSM, a low background SPC installed at Modane underground laboratory (LSM) has been used with Neon gas to search for dark matter particles thanks to a very low energy threshold, around 100 eV. To reach better performances, the next generation of SPC (140cm), NEWS-G_SNO, is under construction. We will present the fabrication method for NEWS_G detectors, low energy calibration with 37Ar and X generator, cleaning methods to remove the surface contamination, measurement of detector background and its interpretation.