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Comment by fabian2k

7 years ago

There are almost certainly oxygen sensors in that room. The helium concentration was probably not high enough to displace enough oxygen to trigger them. Though it wouldn't entirely surprise me if they were ignored or disabled.

Liquid helium is rather expensive and would likely draw attention in areas where it's not usually handled. Really doesn't sound like a useful terrorism tool.

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fabian2k

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afturner  7 years ago

Thanks for the info! Did the article mention that it had to be liquid helium then?

  • fabian2k  7 years ago

    I assumed liquid helium because that is what you need to fill MRI/NMR machines. You could use regular helium, but the pressure bottles are also rather conspicuous. And releasing large amounts from both is not a subtle process, so I really doubt that is practical.

    • afturner  7 years ago

      To be clear, not arguing, I just want to learn. Doesn't this contradict what you said before though, about it not displacing the oxygen sensors in the room because it was so little? "We do not know how much of the 120 liters ended up going outdoors and how much ended up inside. Helium expands about 750 times when it expands from a liquid to a gas, so that’s a lot of helium (90,000 m3 of gaseous He)." I wonder what this would mean in practice at any given time.

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