Patent ID: 7213445

Claim:
A method for measuring particulates density in air including the step of steps of: measuring a speed of a sound wave through the air; and determining the particulates density in the air based upon the speed of sound wave through the air by correlating the changes in sound speeds to the density of the contaminant d imp as the density of impurities, and the average molecular weights of the air by d imp = [ α imp ⁡ ( 1 + α wet ) ⁢ W air ( 1 + α wet ) ⁢ W air - W imp ] ⁢ ( W imp V ) where V is the molar volume of air mixture, W air is the average molecular weight of dry air, W imp represents the average molecular weight of impurities, and α wet and α imp stand for the ratios of speeds of sound caused by relative humidity and presence of impurities in the air, respectively.