I'm still struggling with what "organic" Sulphur is. Organic compounds contain carbon. Elemental Sulphur does not.
Here is the
MSDS for Sulphur Powder. Its ignition temp is about 450F, and can flash over around 405F. You don't typically see those temperatures except inside your oven, or in front of a torch.
That said, just like flour dust, finely powdered sulphur, suspended in the air, can develop a static charge significant enough to flash over. Its rare to get the ratios perfect, but it can happen. Oh, and where it burns, it gives off some REALLY noxious stuff. Hydrogen Sulfide. VERY BAD. Good for making Sulpheric acid, not good for breathing.
If it burns, put it out with water from a hose at the furthest distance you can manage, upwind if possible.
Pure sulphur can also combine with all kinds of common, and uncommon, substances in all sorts of ways at relatively normal temperatures and conditions.
Wear a mask when applying, keep it away from places the birds are likely to dustbathe in it, and keep a pressurized water source handy. Best to apply on humid days. It can be used safely and responsibly - my grandfather kept one of those rubber things you use for getting snot out of bay's noses full of the stuff, and would gently apply some in corners, cracks, and crevices to control bugs.