On ships, as little visible smoke should be produced as possible, and the soot content kept to a minimum. A high soot content on deck can lead to the danger of soot deposits on the passengers. In order to test whether the smoke count of marine diesel engines does not exceed the prescribed limit values, shipping companies (and port authorities) can use a smoke tester. Use of the instrument provides clarity regarding the smoke values. In shipbuilding, the smoke count also plays an important part. After individual components have been assembled (engine, diesel particle filter, exhaust pipe), the soot emissions should be tested. In addition to this, for environmental reasons the customers often make demands regarding the emission values, and require proof of the soot emission in the diesel exhaust. The correct functioning of the diesel particle filter can also be testing using a degree of blackening measurement.