From Guild Wars 2 Wiki
Particle Collector is a device used to sample the miasma near a recently fallen Brandstone. To fill it, use the Brandstone Multitool to locate a fallen Brandstone. Approaching or using the device near a fallen Brandstone replaces the device with Particle Collector (Filled).“
Double-click to take a sample of the miasma surrounding a recently fallen Brandstone.
— In-game description