Measurement of solid, aerosol, vapor, liquid and gaseous concentration and particle size

A method and apparatus for measuring particle content (120) in a stream (140), comprising routing the stream, via a plurality of tubes (220, 230), from a plurality of sampling points where particle content concentrations (132) are to be measured. The concentration of particle content (132) in the stream (140) may be measured. The measurement may be based on determination, via a sensor for example, of an electrostatic charge (212) of the particles (132) as the particles (132), and/or based on counting of a number of particles (132) in the stream (140), such as using a counter tracking light emitted from a light source (312). The measured concentration of particle content (120) may be analyzed to determine if it is indicative of an appropriate concentration of measured particles (132) in the stream (140). The particles may comprise extinguishing and/or suppression agent particles (110). (Fig. 1A)