Mutagenic activity measured by Ames test and by gene conversion, point mutation and mitochondrial mutability in Saccharomyces cerevisiae D7 strain was determined in the indoor environment of a glass factory. The results suggest that the increase in mutagenicity of air sample collected near the machinery is due to the thermal decomposition of oils. Modified assays were therefore compared for their ability to detect mutagens contained in urinary concentrates of exposed workers. The bacterial tests were performed by microsuspension assay in TA98, TA100 strains and in YG1024, YG1029 strains which overproduce O-acetyltransferase. Significant differences are evidenced both in the eukaryotic and prokaryotic systems.