Went on the tour and found it was a lot bigger than I would have thought.
Near to closing time I was shown some great maps (1875) roughly 4ft x 4ft which were similar to 1st pic but of other parts of Birkenhead which I would love to have a digital copy of.
I think there were 85 rows of info + lots of map cases in the temperature controlled rooms and the cylinders for fire control which would immediately starve the fire of oxygen but have still been breathable.

Interesting, Derek; wish I'd gone. According to the light green colour coding on the gas cylinders, they contain an inert gas, probably neon, krypton or xenon, (but not argon which is dark green). As to whether the atmosphere flooded with one of these gases would remain breathable, I have my doubts, since the purpose is to remove oxygen.

Great pics Degs. Glad you enjoyed it.

The old Halon gases - extinguished everything including human life.
Has been replaced throughout EU now by inert gases - mainly because some idiots in Computer Mainframe/Server rooms decided to ignore a fire alert and got 'extinguished' themselves !!!!

derek glad you enjoyed it ,great photos...

The cylinders contain Inergen, a mixture of 52% nitrogen, 40% argon, and 8% carbon dioxide. The amount present has been carefully calculated to lower the concentration of oxygen in the storage halls to a point that cannot support combustion, but is still perfectly breathable by humans - though, quite frankly, I'd rather not be around to test that theory if they ever go off.

Thanks for the definitive answer, marty99fred. Since, because of a lung condition, I can only just manage on the natural air content of about 21% oxygen I'm sure I'd have problems in an Inergen atmosphere.

I believe that the Yanks were buying up all the surplus Argon for use in their fighter planes as it does no damage to the electronics.