I spend much of my work life in datacentres and you do get a bit complacent. Some of the new places with hot/cold aisles are like rat runs and you do have to think about your exit. Many people believe that it's the Halon that will kill you(clearly it will if you don't get out before you run out of oxygen) but you are far more likely to be hurt by 15kg floor tiles flying around and once they start flying then your exit path will be very difficult Some places I seen have 40+ cylinders which can dump in seconds.