The plant rooms at the far end of this large room are very sturdy and, being inside the bunker, are obviously designed to protect the occupants from fire or other hazards arising from their use. The base of what was once a full-height wall can be seen as can the cable access and ventilation holes.
The left-hand room, No 3, housed the air circulation fans used to cool the equipment in the main operations room. The units there generated a great deal of heat so all air circulated in the bunker was first cooled then mixed in the ratio of about 1 part re-circulated to 2 parts fresh before being moved around the rest of the bunker. The middle room, No 1, housed the fan which circulated air around the rest of the bunker but the third plant room remains a mystery. None of the maintenance engineers interviewed can remember what it was used for but the best guess is that it was a spare, stand-by, circulating fan. The concrete beds in front of the doors supported large water tanks which were part of the air cooling system for the air circulating system. The doors seen here are heavy steel and the overall structure is very strong indeed.
The machine bed outside plant room 2, the right-hand one, was used for housing the compressors that ran the refrigeration part of the air conditioning. This strange numbering of the plant rooms, 3-1-2 from left to right (and the signs don’t appear to have been switched around at any time) remains a novel mystery. No-one spoken to can remember why this is so!
