Abstract: Apparatus for volumetric sampling of a particle-laden gas includes a housing defining a sample chamber, a piston movable in the sample chamber so as to vary the volume of the sample chamber and a drive assembly for moving the piston in the sample chamber. The housing includes an inlet for admitting a particle laden gas into the sample chamber and an outlet for carrying the particle-laden gas from the sample chamber. The piston draws a predetermined volume of the particle-laden gas into the sample chamber through the inlet at a first flow rate during an intake phase, and exhausts the predetermined volume of the particle laden gas from the sample chamber through the outlet for analysis at a second flow rate during an exhaust phase. The outlet of the sample chamber is typically connected to a particle sizing instrument for measuring particles in the particle laden gas. The sample volume and the flow rate during the intake phase can be selected to match the parameters of the device or process being analyzed.