A real-time chemical species mass flow rate measurement system comprising: Means for determining bulk flow rate of a flowing fluid; An analyzer , said analyzer having a sampling location located within the physical boundaries of said means for determining bulk flow rate; the flow rate measurement system - is adapted to use calculating means that are also used for other functions in case the mass flow rate measurement system serves as part of a larger measurement system, or - comprises calculating means of its own, said calculating means are each adapted for calculating and reporting mass flow rates of at least one chemical species characterized in that the means for determining bulk flow rate are an averaging pitot tube flow measurement detector , extending in a longitudinal axis, with upstream pressure sensing ports and downstream pressure sensing ports , and with an outer surface provided with windows or openings the analyzer is a laser-based gas concentration detector , a solid-state or electrochemical gas concentration sensor adapted for detecting concentration of at least one chemical species within said fluid, said laser-based gas concentration detector, solid-state or electrochemical gas concentration sensor being physically mounted within said averaging pitot tube to form a single probe for insertion into the fluid; the location of said laser-based gas concentration detector, solid-state or electrochemical gas concentration sensor being displaced longitudinally with respect to the upstream sensing ports and the downstream sensing ports along the averaging pitot tube longitudinal axis, and said analyzer, if it is the laser-based gas concentration detector, being in communication with the bulk fluid by said windows or openings or, if said analyzer is the solid-state or the electrochemical gas concentration sensor, being in direct communication with the surrounding fluid via the openings. Means for determining bulk flow rate of a flowing fluid; An analyzer , said analyzer having a sampling location located within the physical boundaries of said means for determining bulk flow rate; the flow rate measurement system - is adapted to use calculating means that are also used for other functions in case the mass flow rate measurement system serves as part of a larger measurement system, or - comprises calculating means of its own, - is adapted to use calculating means that are also used for other functions in case the mass flow rate measurement system serves as part of a larger measurement system, or - comprises calculating means of its own, said calculating means are each adapted for calculating and reporting mass flow rates of at least one chemical species characterized in that the means for determining bulk flow rate are an averaging pitot tube flow measurement detector , extending in a longitudinal axis, with upstream pressure sensing ports and downstream pressure sensing ports , and with an outer surface provided with windows or openings the analyzer is a laser-based gas concentration detector , a solid-state or electrochemical gas concentration sensor adapted for detecting concentration of at least one chemical species within said fluid, said laser-based gas concentration detector, solid-state or electrochemical gas concentration sensor being physically mounted within said averaging pitot tube to form a single probe for insertion into the fluid; the location of said laser-based gas concentration detector, solid-state or electrochemical gas concentration sensor being displaced longitudinally with respect to the upstream sensing ports and the downstream sensing ports along the averaging pitot tube longitudinal axis, and said analyzer, if it is the laser-based gas concentration detector, being in communication with the bulk fluid by said windows or openings or, if said analyzer is the solid-state or the electrochemical gas concentration sensor, being in direct communication with the surrounding fluid via the openings. <EOS>