This review article describes a list of most common techniques of soot measurement, particularly for in-cylinder diesel engine soot. The techniques presented in this paper are Laser Induced Incandescence (LII), Light/Laser Extinction Measurement (LEM), Light/Laser Scattering Measurement (LSM), Emission Tomographic (ET) and Thermophoretic Sampling. All techniques are briefly elaborated and their principles of operation, as well as their applications and current issues, are covered. It is commonly acknowledged that non-invasive techniques feature some advantages and are more preferable compared to invasive techniques. Besides, more modern technique such as ET is said to be most widely applied in the future due to its high level of accuracy. However, there are possibilities that both invasive and non-invasive methods can complement each other to obtain more accurate soot measurements.
