Abstract: The present invention provides a portable optical particle sensor apparatus and a corresponding particle measurement method. The portable optical particle sensor apparatus is equipped with an optical particle concentration capture device (10) which is set up to determine measured values of an instantaneous particle concentration of predetermined particles in an event-controlled measurement mode, and an event capture device (50; 50?; 50?) for capturing at least one predetermined local event relating to the environment of the optical particle sensor apparatus (10) and for activating the event-controlled measurement mode in response to the capture of the at least one predetermined local event.