Olfactory appraisal of odorants for 100% hydrogen networks

Abstract

To meet carbon emissions reduction targets heat and transport need to be decarbonised. Hydrogen is being considered as a flexible energy vector that could play an important part in this endeavour. With demonstration projects on the rise it is crucial to identify suitable odorants to ensure, safety regulations are met and public acceptance gained. Specifically, this work investigates the use of sulphur based odorants currently in use in the UK and Europe, alongside sulphur-free and experimental ones, for use in a 100% hydrogen gas demonstration network in the UK. Gas samples odorised with five different odorants are analysed to determine odour detection threshold, the odour intensity, its hedonic tone and character. The tests are performed by an accredited laboratory following EU standards. The results show that four odorants meet requirements as stenching agents for use in UK gas distribution network, whilst one, 5-ethylidene-2-norbornene, fails to demonstrate an unpleasant odour.

A comparative study of odorants for gas escape detection of natural gas and hydrogen

“…This increases the sensitivity of the results to the individual participant's olfactory sensitivity. Despite these variations, if we compare our findings to previous olfactory testing from Mouli-Castillo et al (2020), which was performed on odorised hydrogen using standardised tests in an accredited laboratory, we find that the odorant concentration in air from our work are within an order of magnitude from those presented in that study. More specifically, our detection thresholds for Hydrogen with New Blend, Standby Odorant 2 and THT, are 6.15, 4.5 and 2.2 times greater than the ones from that study respectively.…”

“…However, our study addresses the lack of investigation into the olfactory response to odorised hydrogen compared to natural gas, for an equivalent end use aimed at combustion appliances. This work complements a previous study by Mouli-Castillo et al (2020) which investigates the likely olfactory characteristics of odorised hydrogen delivered to consumers via a distribution network. The Mouli-Castillo et al (2020) investigation focused on applying standardised olfactory tests to odorised hydrogen.…”

“…This work complements a previous study by Mouli-Castillo et al (2020) which investigates the likely olfactory characteristics of odorised hydrogen delivered to consumers via a distribution network. The Mouli-Castillo et al (2020) investigation focused on applying standardised olfactory tests to odorised hydrogen. This method provided quantitative information, using reproducible tests, but not a direct comparative assessment with odorised natural gas.…”

“…To account for this bias, the research was designed as a comparative study, assuming that any bias from the untrained participants would apply equally to all gases and odorants tested. Further confidence can be had by comparing the findings with standardised tests' results, although these usually lack the comparative element added by this study (see discussion section) (Mouli-Castillo et al, 2020). This allows a useful comparative analysis.…”

“…A target odorant concentration of 2 ppm was achieved by diluting the odorised gas (at 20 ppm) with the equivalent un-odorised gas according to the test specifications (Supplementary Table 3). 2 ppm is the concentration used in the UK gas network (Mouli-Castillo et al, 2020). The specification for the odorant and gas mixtures used for the experimental work were provided by the National Physical Laboratory, and supplemented their research programme on the odorisation of hydrogen for gas distribution networks.…”