Oxygen-breathing beings are not supposed to be in a room being filled with Halon

Not halon but there are fire supessant gas mixtures (e.g. Inergen(R)). These gases have a interesting physiological effects that increases the breathing frequency and therefore allow surviving in a flooded room.

Statement from ING's head of reatail banking; it was in fact a test with "Inergen" gas

http://webcache.googleusercontent.com/search?q=cache%3Awww.i...

True, but there is a chance of humans being in the room when a fire breaks out. That's why they breathing apparatus scattered around (hopefully).

Halon is extremely dangerous and most datacentres built in the last twenty years avoid using it for that reason.

The last halon datacentre I was in had breathing apparatus within easy reach no matter where you were standing in the place. Two paces, at most, to grab a mask. You do have seconds if it goes off, and that mask is only to give you enough time to run out of the room.

The newer stuff is less hostile to organic life, so there's no reason for a respirator.

I don't think of the DCs I've seen have breathing apparatus around - they rely on strictly enforced signin sheets (so when the alarm goes off, a person outside the room immediately looks to see how many people are in the DC), and a 30-45 second delay to evacuate the DC before the suppression system activates.

Halon is not too toxic and you only need a concentration of less than 10 % for it to be effective. And I even once read that Halon helps breathing, i.e. in the presence of Halon humans can survive at a lower oxygen concentration than they normally could but I am unable to find a source right now. All in all it is probably not to bad to be in a room flooded with Halon and the fumes of burning stuff are probably the larger hazard.