Oxygen Deficiency Hazard Induced by Helium Release in Accelerator Tunnel

Tests to investigate oxygen deficiency levels due to release of helium into the CBA tunnel are described. Results of the tests indicate that the helium stratifies and spreads quickly in the horizontal plane. This demonstrates that adequate warning of possible asphyxiation hazards can be achieved. When oxygen deficiency monitors are located at ceiling level they may be spaced at intervals of 60 m. or more and still achieve acceptable results.