It seems from my googling research and adding a bit of physiology that the Inergen is Argon, Nitrogen and Carbon Dioxide.
It is designed to reduce the atmospheric oxygen to low, but not unsurvivable levels for oxygen breathing humans. It contains more CO2 than air, thus stimulating increased depth and rate of respiration to compensate for the reduced oxygen levels necessary for fire suppression.
I would imagine it might convert tackling the fire escapes into attempting the hilary step, but would still be breathable, and allow escape whilst suppressing fire.
They seemed to only have it hooked up to the switch rooms with big doors on, to keep it confined: maybe thats where all the BIG fuses lived?!