Almost any finely-divided organic material, eg flour, will produce an explosive mixture in an air suspension. The stuff which a vacuum cleaner picks up is mostly skin cells and other forms of organic dust.
Today’s invention is to make a self-powered vacuum cleaner.
It contains a small combustion chamber which admits some aerated incoming dust and periodically ignites this to explode, driving a piston which in turn powers the cleaner’s fan. Obviously a small, battery-powered starter motor would be required to initiate the airflow.