Powdered Sugar Birthday Cake Bursts Into Flames

Powdered sugar pretty innocuous.

In fact, a pile of powdered sugar is barely flammable at all. Those candles there could probably be upturned into the surface of the cake with almost no risk of danger to anybody around.

Then comes the dispersal.

See, mom didn't think about the fact that taking that same powdered sugar and dispersing it - increasing its surface area, mixing it far more thoroughly with the oxygen in the air - would turn an non-combustable material into a potential fireball.

It's kind of like the lycopodium powder fireball.