Patent ID: 8717550

Claim:
Method for detecting biological material in an airstream, which airstream contains particles of biological material and biologically inert material, in which method the airstream is fed with the aid of sampling devices into a chamber and out of the chamber after sampling, a light beam is emitted towards the airstream by a light source, in order to excite the particles in the airstream, in order to create fluorescence, the fluorescence emitted by each particle struck by the light beam is measured with the aid of first measuring means and a fluorescence signal depicting the fluorescence is created, the scattered light from each particle struck by the light beam is measured with the aid of second measuring means and a scattering signal depicting the scattering of the light is created, the fluorescence signal and the scattering signal are converted into discrete values at the sampling frequency, and the discrete values are recorded cumulatively as hit points in an at least 2-dimensional measurement space equipped with selected dimensions, an alarm value, showing the presence of a selected biological material, is defined by using a preselected criterion, characterized in that, in the method said fluorescence signal is created from emission measured from one or more particles being simultaneously in the chamber, said scattering signal is created from scattered light measured from one or more particles being simultaneously in the chamber, at least one index area is preselected from the said measurement space, a cumulative index is calculated at an index frequency from the hit points accumulated on the each preselected index area, the device is arranged to sample the fluorescence signal and scattering signal continuously, the sampling frequency is 100 kHz-2 MHz.