ISO 17071:2006 specifies two alternative methods for determining the fogging characteristics of leathers used in the passenger compartments of motor vehicles, namely Method A and Method B. These are two different test procedures to measure the volatile components and there is no mathematical correlation between the results obtained with Method A and those with Method B.

Method A determines by reflection the light scattering properties (or opaqueness) and the nature of the film or droplet formation from volatile components condensed on a cold glass surface. Method B measures gravimetrically the quantity of volatile components condensed on a cold aluminium foil surface. Annex A gives the results of inter-laboratory trial which show that Method B performs well, whereas Method A showed a large variation in the percentage reflection.

The test conditions allow the two tests to be carried out in succession.