The soot testing method involves taking a specific amount of flue gas from the connection between the heating appliance and the chimney, behind the heat exchanger in the core of the flue gas stream, and passing it through a special filter paper. The resulting soot spot is compared with the differently blackened areas of the soot comparison scale to determine the soot number.

The advantages of the BRIGON soot tester lie in its low weight as well as its simple and reliable handling.