Despite the name “canned air”, computer duster isn’t oxygen at all. It’s actually 1,1-Difluoroethane kept under pressure in its liquid form and released as a freezing cold gas. It can cause moderate frostbite. It can get you high if you huff it (but don’t do that — it’s a truly awful idea.) And it makes boiling water explode. Wait, what?
The easy hypothesis is that the temperature difference between boiling water and liquid 1,1-Difluoroethane causes the duster to rapidly and violently convert into its gaseous state. But TheBackyardScientist gave the same experiment a shot with liquid nitrogen and liquid butane. No dice. To make matters stranger, butane has an even lower boiling point than duster.
So what's going on here? The Backyard Scientist speculates it has something to do with duster and water both being polar molecules, while nitrogen and butane are not. I’m no scientist, backyard or otherwise. All I know is that if I were planning on making boiling water explode, shorts wouldn’t be my first choice of clothing.
Feel free to speculate on matter scientific and otherwise in the comments.