In 1981, workers at LANL were about to fill hydrogen (H2) cylinders from a large, H2-filled tube trailer. They used a manifold containing residual oxygen (O2), which was also connected to a tube trailer of O2 with only one valve separating these incompatible gases. When the mix ignited, the workers attempted to purge O2 from the manifold using low-pressure H2. The resultant fire destroyed the valve, allowing high-pressure O2 to flow into the low-pressure H2 tube. The subsequent large mix of O2 and H2 resulted in an explosion.