A dust explosion is the fast combustion of dust particles suspended in the air in an enclosed location. Coal dust explosions are a frequent hazard in underground coal mines, but dust explosions can occur where any powdered combustible material is present in an enclosed atmosphere.
User throws a pouch filled with iron powder and flour at opponent. Opponents will naturally destroy the suspicious projectile causing a grey cloud to explode from the bag in a wave. Then all user has to do is set it a spark. The iron dust and flour floating in the air around opponent is highly dangerous. All it needs is a small spark to ignite the flour and the area will go up in a giant fireball.