Remember that most people who perish in building fires are actually overcome by fumes (gases) from combustion of man made materials, rather that "smoke" or other particles.
That's one of the things that really amazed me about 9/11. There was a ridiculous amount of just nasty soot-laden black smoke. Closest comparison I could make is the smoke that comes from burning tires, but on a massive scale.
My house in NJ is about 15 miles away and you could easily smell it in the air, it was terrible. It's no wonder people got seriously ill from breathing that stuff in.