Page "1996 Channel Tunnel fire" Paragraph 19
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Fire detectors are located at intervals of 1. 7 kilometres along the length of the tunnel.
These consist of a series of different types of detector: optical, ionic and carbon monoxide.
The system is set such that if any two go off together, it raises a confirmed alarm in the FEMC and RCC.
If only one of the three goes off, it raises an unconfirmed alarm in the FEMC.
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