ISO/TS 23556:2007 specifies a multipass soot-filtration test method using batch thermal gravimetric analysis (TGA), continuous online Fourier Transformation Infrared (FTIR), or other approved soot-measuring techniques for evaluating the initial filtration efficiency of single-stage, multiple-stage, centrifugal and other soot-removal devices (SRD) for internal combustion engines submitted to a constant flow rate of test liquid. The test procedure determines time-weighted average initial soot-removal efficiency for soot-removal devices. This test method is intended for application to SRD having a rated flow between 0,5 l/min and 75 l/min.