There are runs where the people run through dust bombs thrown at them from the spectators. Doesn’t sound smart to be running (and sucking in lots of air) while people through colored dust at you.
Have to admit - I hadn’t thought of it catching on fire though - I always thought that was more of in a confined space like a silo. But probably wouldn’t have to be.
I grew up in Kansas where there are grain elevators everywhere. In the old days, elevator fires and explosions were not uncommon. By the time I was born, they had worked out the safety regulations and I don’t remember one ever happening. But, boy, I heard the stories.
I remember thinking how unfair it was... You go to work not thinking you were in any kind of particular danger, then BOOM!... Pearly Gates.
It doesn’t necessarily take grain dust to get an explosion. AFAIK, most any dust or powder or small suspended particles of any kind will work, even stuff you don’t normally think of as being combustible. I think what matters is size of the particles, the type of particle, their concentration, the charge on them, the right concentration of air or other gasses, a spark, probably a few other factors (I’m no expert), and you’ve got a very dangerous situation. Like someone else said, it’s the basis of those fuel-air bombs the military has nowadays. It’s also why, for example, you have to be careful about storing gasoline indoors. You’re not worried about the gasoline itself exploding. You’re worried about fumes escaping from the container and creating one of these explosive situations.