external exposure facility PULEX-COSMIC SILENCE The PULEX-COSMIC SILENCE facilities at the Gran Sasso National Laboratory (one of the four national laboratories of INFN, Italy) exploit the deep underground location — shielded by 1400 m of rock — to provide an environment where cosmic ray flux is reduced by a factor of ~10⁶, creating an extremely low radiation background for biological experiments. The PULEX cell culture facility and the adjacent climate-controlled COSMIC SILENCE animal facility (housing Drosophila melanogaster and other model organisms) allow investigation of whether normal environmental radiation is required for maintaining cellular defence mechanisms. Experiments have demonstrated that reduced background radiation decreases cells' protection against chemical radio-mimetic stressors, with the facilities open to external collaborators. Located at Gran Sasso National Laboratory-National Institute for Nuclear Physics (LNGS-INFN). Fratini et al. Radiat Environ Biophys 54:183, 2015 website Paul Schofield