The point is, since it was deliberate, the person could almost as easily blocked both stairs. It's not comparable to an accidental fire that potentially impress a single staircase
Part of modern US stairwell regulation also learned from 9/11, where they found out it wasn't a great idea to have all the required stairwells very close to each other either.
2 stairways are much harder to block than one, especially if they are at opposite ends of the structure. One person will struggle to keep them blocked.
Fire extinguishers are remarkably effective at opening locked doors, FYI. And a surprising number of people are not only aware of this fact, but remember where the fire extinguishers are.
Some folks would get stuck and not get out, but it generally requires dedicated eyes on a crowd if you want to keep them inside something for any length of time. Hence prison guards, locks being a dedicated profession, etc.
"Police quoted witnesses who saw a man walking into the clinic with a paper bag, which he put on the floor, right next to a heater by the reception desk, and kicked it. Liquid poured out, caught fire and the whole floor was in flames and smoke."
Don't really need to be an expert in starting fires.
If an accelerant is used that is continuously burned until exhausted , then I'm not sure it matters where or what materials are present. If there is a fire at an exit that persists and is difficult to extinguish, said arsonist can then move to the next exit, and perform the same action. Thus blocking multiple exits while acting as a single individual. That's my point.
It’s surprisingly hard to put enough accelerant in a place to burn awhile (5-10 minutes?) in a way that can’t be interfered with and will keep going without tending, without drawing attention to yourself while doing so if anyone is paying attention. Most
portable methods (gasoline can?) are so volatile it is just going to explode almost
immediately and are easy to recognize as a hazard.
Certainly not impossible, but it requires more craftiness and more prep the more complicated we get.
Which hopefully there aren’t that many folks who are likely to do so. And if someone does, we can catch them fast.
Basic redundancy is a good idea (n=2) in general, for many many reasons. Maintenance doesn’t take out the only way out for instance, or a single fight or accident doesn’t leave someone stuck.
N=5 is probably overkill for anything for a huge convention center.
