Simulating latrine conditions to assess perfume performance against malodour

Abstract

To evaluate perfume performance in toilets, we built model toilets in which critical factors such as background malodour, climate, and airflow were controlled. The models were equipped with an odour generator that injected hydrogen sulfide, methyl mercaptan, butyric acid, para‐cresol, and indole, allowing us to accurately and reliably reconstitute toilet malodour headspace. The malodorant concentrations matched the quantitative headspace analysis performed in African and Indian toilets. The toilet malodour headspace performance was validated by chemical and sensory analysis. Olfactory stimuli were presented to participants in different simulated climates to assess the effect of climate on the perception of odours. The sensory data show that increasing temperature and humidity decreased the intensity ratings of odours without altering their quality. Perfume can be delivered in these toilets by forced evaporation to control the headspace concentration, or by delivery systems such as cellulosic pads, liquids, and powders. Our experimental set‐up allowed us to establish dose–response curves to assess the performance of a perfume in reducing toilet malodour and increasing perceived pleasantness.

Modification of Major Contributors Responsible for Latrine Malodor on Exposure to Hypochlorous Acid: The Potential for Simultaneously Impacting Odor and Infection Hazards to Encourage Latrine Use

“…For example, a 1.7-m 3 latrine used to assess perfume performance on latrine malodors would be expected to contain, under the dirtiest conditions, 2.6 μg of indole and 15.3 μg of p-cresol based on previous GCMS headspace analysis. 21 , 38 These masses would require less than 2 mL of aerosolized HOCl solution (100 ppm) for > 95% modification based on our chemical analysis studies. Similarly, the concentrations of DMDS and DMTS tested were > 2,000 times higher than the odor detection threshold from the headspace of ethanol/water solutions at concentrations of 9.1 and 0.4 μg/L, respectively.…”

“…Odor control in latrines has recently been brought to the world stage with a variety of collaborations including one between the Bill & Melinda Gates Foundation project Reinvent the Toilet Challenge and Firmenich SA that has successfully identified the compounds responsible for the odors in latrines and developed perfume to improve the overall latrine environment. 11 , 21 , 38 Hypochlorous acid offers an opportunity for an alternative intervention that could significantly modify most of the identified malodor compounds, and therefore the sensory perception, and simultaneously bring about improved sanitation within the latrine environment. HOCl as an alternative offers stability at ambient and elevated temperatures, potency, low cost, and the prospect of modifying noxious chemical compounds and inactivating infectious microbes.…”

Odour assessment of school toilets in Gauteng, South Africa – before and after bioremediation

“…The olfactory test was adapted from Chappuis et al (2016), which made use of 'Sniffin' Sticks' containing the key odour causing compounds for stale urine and faeces. Each 'Sniffin' Sticks' perfumer (Figure 3) contained one of the compounds responsible for the most common odours found in toilets, namely: butyric acid, indole, p-cresol and dimethyl trisulfide (Chappuis et al, 2015, Chappuis et al, 2018. In addition, one 'Sniffin' Stick' contained a mixture of chemicals to mimic faecal odour and another mixture for mimicking stale urine odours.…”

Fecal Malodor Detection Using Low-Cost Electrochemical Sensors

“…This is because odor perception by humans varies based on each individual sensitivities. In addition, congruent (i.e., additive) and antagonistic (i.e., canceling) effects between odorants will alter human perception [13]. Even so, there is a great need to develop compact electronic and real-time methods to detect and quantify odors, particularly for situations where continuous odor monitoring is required, as in the case of novel toilets and sanitation technologies.…”