Or even Contamination Control:
The ISO4572 (BS6275/1) test is where fresh contaminant is injected into a test hydraulic circuit - contaminants not removed by the test filter are recirculated, thus simulating typical Le Mans Toilet conditions of the late 1980's. The filter's ratio
beta is multiplied by the number of particles larger than 'x' upstream of the toilet seat
divided by the number of particles downstream.
The micron size at which
beta = 75 is the most commonly accepted definition of absolute.
In other words - make sure your turds are smaller in diameter than the 100mm pipe they use to suck out the cess-tank with, or you will see them again