consumer decide to refill a certain diffuser with a different liquid (e.g. another brand which may contain more volatile solvents/fragrances), an involuntary exposure to very high concentrations of these substances may occur. As Nazaroff and Weschler (2004) pointed out, the risks of air fresheners can be clearly defined and assessed, the benefits, however, remain very subjective. Acknowledgments Special thanks are due to Ms Doreen Markewitz and Ms Astrid Schwarz for GC/MS evaluation. Mr Christian Fauck's assistance with PTR-MS operation and Ms Jenny Bartsch's help in experimental work is greatly appreciated.