A laser spectrophone operated at 514.5 nm has been shown to accurately monitor the “graphitic” carbon component of the airborne particulate emitted in the exhaust from a 2.3 liter Opel diesel vehicle. The mass-specific absorption coefficient of the graphitic-like material is 8.9±0.5 m2/g at 514.5 nm, in excellent agreement with values for similar material from other combustion sources. Since the laser spectrophone can apparently be used to quantitatively measure light absorption by airborne “graphitic” particulate material, it may also be generally useful as a monitor of “graphitic” particulate mass loading, regardless of combustion source.