An assessment of VOC emissions and human strength perception of liquid electric fragrance diffusers†

Fragrance products are commonplace in everyday life and their air quality effects extensively studied. In this study the use of multiple plug-in diffusers (liquid electricals/LEs) was assessed by quantifying air concentrations in controlled test rooms (‘toilet booth’ and ‘large booth’) with up to 5 LEs of known formulation in concurrent use. Olfactive strength tests were completed under the same conditions in blind assessments. Air samples were analysed using thermal desorption – (TD) gas chromatography (GC) coupled to flame ionisation (FID) and mass spectrometry (MS) detectors. Significant positive linearities were found for several VOCs (e.g. α-pinene toilet booth and large booth R = 1 and p = 0.0028, p-cymene toilet booth R = 0.94 and p = 0.017, large booth R = 0.89 and p = 0.033), with α-pinene presenting the highest measurable gas-phase concentration (mean 25 μg m⁻³, toilet booth with 5 LEs present). All measurable linearities for fragrance species in toilet booths were significant. However, olfactive intensity assessment showed a plateauing in fragrance perception after the addition of 2 LEs. Only very volatile fragrance ingredients such as α-pinene and benzaldehyde could be detected in the gas phase, but at ambient concentrations that were always lower than literature values for their individual odour detection thresholds. The plateauing of the perception of fragrance strength may aid in limiting potential off-instruction use, thereby limiting end-user exposure to potentially high concentrations of emitted VOCs. The drivers of human fragrance perception here appeared to be lower vapour pressure constituents of fragrance formulations like sesquiterpenes. Moderation of the concentration of monoterpenes used in room fragrance formulations may be a practical solution in limiting possible air quality impacts of product use, whilst still maintaining end-user fragrance perception.