When odors linger in clothing after a meal, does the mixture of compounds released from the fabric differ as well as the intensity? A study exposing cotton, wool, and polyester to hot-pot steam or tobacco smoke found differences between fabrics in the compounds detected and their relative proportions.
Alongside chemical analysis, the study used a numerical model to examine how airflow and spaces within fabric affect release. However, the original paper contains inconsistencies in key explanations of the model. We need to distinguish what the measurements established from what remains difficult to conclude.
Measuring compounds released from fabrics exposed to hot pot and tobacco
The study, published online in 2022, used cotton, wool, and polyester fabrics that had been washed three times beforehand. Sample areas were equal, but cotton and polyester were thick terry fabrics, whereas wool was a thinner twill. This was not a comparison in which only fiber type changed while thickness and structure were fully matched.
For the tobacco condition, fabric was suspended near the top of a closed experimental chamber while three cigarettes burned simultaneously below, then left for one hour after combustion. For the hot-pot condition, 150 g of commercial soup base was heated with 750 mL of water, and fabric was exposed for one hour after boiling began.
The researchers then cut out the central portion of each fabric and analyzed compounds released into the headspace of a sealed vial using gas chromatography–mass spectrometry, or GC-MS. Measurements were performed three times, with the median used. Compounds were tentatively identified from matches to a mass-spectral database, not definitively identified by comparison with reference standards. No human smelling test evaluated intensity or unpleasantness.
The original compound tables contain unclear entries, including mismatches between names and identifiers, and two entries corresponding to anethole listed at the same retention time but with separate areas. The discussion below is limited to representative examples for which the names, molecular formulas, and identifiers can be matched.
Different compounds stood out in cotton and wool after hot-pot exposure
Compounds tentatively identified as hexanal, nonanal, and β-pinene were detected from fabrics exposed to hot pot. In relative peak-area terms, hexanal and nonanal accounted for larger shares in cotton than in wool or polyester.
By contrast, the peak tentatively identified as β-pinene in the paper accounted for 34.82% of the area in wool, 7.32% in cotton, and 6.93% in polyester. Exposure to the same hot-pot steam did not lead to the same balance of compounds subsequently measured from each fabric.
These percentages describe the relative sizes of peaks captured by the analytical instrument. They do not directly indicate how many times greater the mass of β-pinene released from wool was, or how many times stronger its overall odor was. Instrument response and the concentrations people can perceive also vary between compounds, so comparisons of proportions and of perceived odor need to be made separately.
Tobacco compounds also differed in their detection across fabrics
In the tobacco condition, compounds tentatively identified as nicotine and phenol were detected from all three fabrics. Fewer compounds were reported for wool than for cotton or polyester, and 3-ethenylpyridine, a tobacco-smoke marker, was not detected from wool. Peaks including furfural and 3-ethenylpyridine were observed for cotton and polyester.
The authors considered fiber chemistry, moisture uptake, and fabric structure to be involved in adsorption and release. Cotton cellulose and wool proteins, for example, have sites that can interact with molecules. However, because thickness and weave also differed in this experiment, the differences cannot all be attributed to fiber chemistry alone.
Moreover, failure to detect a compound in the headspace does not necessarily mean that none adhered to the fabric. Unless adsorbed and released quantities are measured separately, retention remains a possibility. The study cannot be used to rank fabrics by health safety.
A model of release rates, and inconsistencies in the original paper
The other main component of the study was a numerical model of mass transfer through fabric thickness. Using nicotine as a representative compound instead of the full complex smoke mixture, the researchers modeled cotton fabric while varying inlet air velocity, the volume fraction occupied by fibers, and molecular diffusivity. This was separate from directly tracking measurements from the three fabrics over time.
In the calculations, higher inlet air velocities produced faster decreases in nicotine concentration inside the fabric. Under conditions of lower diffusivity, concentration differences between the air-entry side and the deeper region became larger, with material remaining deeper inside. Results differed according to the location examined, so a simple claim that lower diffusivity causes the same retention everywhere would be inappropriate.
For the spaces within fabric, however, the abstract states that lower porosity leads to a faster concentration decrease, while the results and conclusion state that a lower fiber volume fraction leads to a faster decrease. A lower fraction occupied by fibers means a higher fraction of empty space, so these statements point in opposite directions. This article does not determine the direction of the porosity effect from this paper alone.
Airflow conditions are also inconsistent: the methods list 1, 10, and 100 m/s, while the results list 1, 50, and 100 m/s. Because of such discrepancies, using the model’s numbers as guidance for household ventilation or airing time requires verification of the calculation conditions and testing with actual fabrics.
Summary
After exposure to hot-pot emissions or tobacco smoke, cotton, wool, and polyester differed in the combinations and relative proportions of compounds detected. For hot pot, specific differences included higher proportions of hexanal and nonanal in cotton and a higher proportion of β-pinene in wool.
The numerical model illustrates how airflow and molecular diffusivity relate to where compounds remain within fabric and for how long. However, the original paper is inconsistent about the direction of the porosity effect and some calculation conditions. It examines both the selection of compounds retained by fabric and the process of release, but further verification is needed before translating the model into practical deodorizing conditions.
The original paper reports support from the Shanghai Engineering Research Center for Clean Production of Textile Chemistry and thanks engineers at Wuxi Little Swan for discussions. The authors declared no conflicts of interest.
Reference
Huang W, Liang S, Zhang H, Ding X, Wang J. Tobacco and Hot Pot Odor Adsorbed by Cotton, Wool, and Polyester Fabrics: Desorption Components and Dynamic Analysis. AATCC Journal of Research. Published online in 2022. doi:10.1177/24723444221132330
