In order to validate our method, a series of personal and
area samples were taken in a factory of a large manu-
facturing ®rm by both our team and the ®rm's labora-
tory, which has acquired a great deal of experience in the
sampling and measurement of nitrosamines. Pairs of
ThermoSorb/N tubes were placed side by side at the
same workplaces (vulcanisation, quality control, forklift
truck drivers, storage). Both laboratories were free to
choose the analytical materials and techniques they
wanted to use. The same calibration mixture of nitros-
amines was used by both.