Table 1. VOCs most prevalent in human breath.
| Name | CAS |
| Toluene | 108-88-3 |
| p-Xylene | 106-42-3 |
| Benzene | 71-43-2 |
| Ethylbenzene | 100-41-4 |
| Acetone | 67-64-1 |
| Decane | 124-18-5 |
| Undecane, 2,6-dimethyl- | 17301-23-4 |
| Undecane | 1120-21-4 |
| Styrene | 100-42-5 |
| Tetradecane | 629-59-4 |
| Nonane, 2-methyl- | 871-83-0 |
| Nonane, 3-methyl- | 5911-04-6 |
| Decane, 5-methyl- | 13151-35-4 |
| Octane, 4-methyl- | 2216-34-4 |
| Cyclopropane, ethylidene- | 18631-83-9 |
| Decane, 3,7-dimethyl- | 17312-54-8 |
| Propanoic acid, anhydride | 123-62-6 |
| 1-Hexanol, 2-ethyl- | 104-76-7 |
| Dodecane | 112-40-3 |
| 1-Propene, 1-(methylthio)-, (E)- (isoprene) | 42848-06-6 |
| Furan, 2-methyl- | 534-22-5 |
| Cyclohexane | 110-82-7 |
| Tridecane | 629-50-5 |
| Hexane | 110-54-3 |
| Nonane, 2,6-dimethyl- | 17302-28-2 |
| 2,4-Dimethyl-1-heptene | 19549-87-2 |
| Methyl vinyl ketone | 78-94-4 |
| Cyclohexene, 1-methyl-4-(1-methylethenyl)-, (S)- | 5989-54-8 |
| Heptane, 2,2,4,6,6-pentamethyl- | 13475-82-6 |
| Decane, 2,2,8-trimethyl- | 62238-01-1 |
| Hexane, 2,2-dimethyl- | 590-73-8 |
| Benzene, 1-methyl-2-(1-methylethyl)- | 527-84-4 |
| Cyclopentane, 1,2-dimethyl-, cis- | 1192-18-3 |
| Cyclooctane, 1,4-dimethyl-, cis- | 13151-99-0 |
| Decane, 4-methyl- | 2847-72-5 |
| Octane, 6-ethyl-2-methyl- | 62016-19-7 |
| 1,3-Pentadiene, (Z)- (isoprene) | 1574-41-0 |
| Hexane, 3-methyl- | 589-34-4 |
| 1,3,5-Trioxane | 110-88-3 |
| Benzene, 1-ethyl-3-methyl- | 620-14-4 |
| Heptane, 2-methyl- | 592-27-8 |
| Bicyclo[3.1.1]hept-2-ene, 2,6,6-trimethyl-, (ñ)- | 2437-95-8 |
| Heptane | 142-82-5 |
| 2,2'-Bifuran, octahydro- | 1592-33-2 |
| Pentane, 2,3,3-trimethyl- | 560-21-4 |
| Propane, 1-(methylthio)- | 3877-15-4 |
| 1-Octanol, 2-butyl- | 3913-02-8 |
| Dodecane, 2,7,10-trimethyl- | 74645-98-0 |
VOCs in breath and air were quantified according to the ratio of their abundance to an internal standard, and ranked according to their alveolar gradient (abundance in breath minus abundance in ambient room air). Alveolar gradient varies with rate of synthesis minus rate of clearance, so that VOCs with a positive alveolar gradient generally represent products of metabolism, though they can also arise from recently ingested foodstuffs and toxins. VOCs with a negative alveolar gradient generally represent degradation of VOCs ingested from ambient room air.