a real - time particulate matter measuring system includes a hot diluter for receiving and diluting aerosol . an evaporation unit receives the diluted aerosol . a cold diluter receives and dilutes the output flow from the evaporation unit . a condensation particle counter receives the diluted output flow and measures the particle number concentration . an integrated device also receives the diluted output flow . the integrated device measures at least one of particle diameter concentration and particle surface area . the integrated device also measures mass concentration .