To be perfectly honest, that was my very first reaction when I first watched the video: it looked like the fuming aftermath of Something Really Bad, and then BO

To be perfectly honest, that was my very first reaction when I first watched the video: it looked like the fuming aftermath of Something Really Bad, and then BOOM! Something Really Bad unfolded on-screen. I figured that it must’ve been some kind of aerosol/powder combustion triggered by the fireworks’ conflagration, but then more learned analyses of cloud hue and knowledge of what was actually stored in situ (correctly) overrode my initial reaction and the fertilizer was identified as the main culprit.