Abstract: A method for determining airborne concentrations of an ensemble of particulate matter below the size fraction 2.5 ?m in aerodynamic diameter (PM2.5). The method is to be composed of a sharp cut PM2.5 cyclone, optical sensor capable of producing scattering coefficients dependent on particle size, temperature and humidity sensors for adapting to changes in the environment, and a processing system for applying logic-based algorithm to convert raw sensor values into PM concentrations. The optical sensor is a dual wavelength integrating nephelometer capable of yielding particle characteristic scattering coefficients at two wavelengths. The particle scattering ratios between two wavelengths are used in conjunction with temperature and humidity in the method's algorithm to reduce particle growth bias and to ultimately yield PM2.5 concentrations.

Abstract: An extruder control arrangement in which the time taken to deliver a known quantity of extrudate is maintained within closely controlled limits by feedback circuit which controls the rate at which plastics material is fed to the extruder.