The invention relates to a non-crosslinked natural rubber latex composition for an inflatable stopper comprising a homogeneous mixture of: a) natural rubber latex; b) a surfactant; c) an amine based chemical antiozonant; d) possibly ammonia and preferably e) single or double wall electrically conductive nanotubes. The invention furthermore relates to an ozone resistant inflatable stopper comprising non-crosslinked natural rubber latex and fiber reinforcement, the rubber having an ozone resistance according to ISO 1431/1 at 50 pphm concentration ozone at 23±2° C., for the time frame of 48 hours, atmospheric humidity of 55% and strain static exposure of 20% and preferably a surface resistivity lower than 100 GΩ according to DIN EN 60079-32-2 and DVGW G 5621-3 (VP) measured at 1000 V and a maximum relative humidity of 30%.