Table 3. The frequency of identified VOCs in exhaled breath of study groups (percentage of observations in each group) .
| Variables | Exposure | Negative control | Positive control | Smoker | Total |
| Acetaldehyde a | 15 (75) | 13 (65) | 4 (100) | 19 (76) | 51 (74) |
| 2-methyle propane | - | 9 (45) | 2 (50) | 13 (52) | 24 (35) |
| Ethylamine | 1 (5) | 2 (10) | 2 (50) | 9 (36) | 14 (20) |
| 2-methyle 1-proanol | - | 3 (15) | - | - | 3 (4) |
| 2-pentene | - | 3 (15) | 2 (50) | 13 (52) | 18 (26) |
| Isoprene | 20 (100) | 20 (100) | 4 (100) | 25 (100) | 69 (100) |
| Acetone a | 20 (100) | 20 (100) | 4 (100) | 25 (100) | 69 (100) |
| 2-propanol a | 12 (60) | 3 (15) | 3 (75) | 3 (12) | 21 (30) |
| 1-3 cyclopentadiene | - | - | 2 (50) | 10 (40) | 12 (17) |
| 1-3 cyclohexadiene | - | 2 (10) | - | 7 (28) | 9 (13) |
| Decane | 16 (80) | 6 (30) | 3 (75) | 8 (32) | 33 (48) |
| Acetonitrile a | 6 (30) | 3 (15) | 3 (75) | 18 (72) | 30 (44) |
| 3-methyle pentane | - | 3 (15) | 1 (25) | 7 (28) | 11 (16) |
| Butene | 15 (75) | 15 (75) | 3 (75) | 15 (60) | 48 (70) |
| 1-3 butadiene | 12 (60) | - | 3 (75) | 16 (64) | 31 (45) |
| 2-4 hexadiene | 4 (20) | - | - | 17 (68) | 21 (30) |
| 3-chloro methane a | - | 2 (10) | - | - | 2 (3) |
| Octane | - | 5 (25) | 2 (50) | 11 (44) | 18 (26) |
| Benzene a | 20 (100) | 20 (100) | 4 (100) | 25 (100) | 69 (100) |
| Acetic acid a | 8 (40) | 9 (45) | 3 (75) | 8 (32) | 28 (40) |
| 2-5 dimethyl furan | 4 (20) | - | 3 (75) | 18 (72) | 25 (36) |
| Propanthiol | 20 (100) | 13 (65) | 3 (75) | 13 (52) | 49 (71) |
| 3-hydroxy 2-butanone | 19 (95) | 11 (55) | 1 (25) | 8 (32) | 39 (56) |
| Heptanoicacid a | 19 (95) | 12 (60) | 2 (50) | 20 (80) | 53 (77) |
| Nitro propane | - | - | 1 (25) | - | 1 (2) |
| Toluene a | 20 (100) | 20 (100) | 4 (100) | 25 (100) | 69 (100) |
| Hexanal a | 20 (100) | 11 (55) | 4 (100) | 16 (64) | 51 (74) |
| Pentadecane a | 20 (100) | 12 (60) | 2 (50) | 13 (52) | 47 (68) |
| Butanoic acid | 14 (70) | - | 3 (75) | 17 (68) | 34 (50) |
| Ethyl benzene a | 5 (25) | - | 3 (75) | 6 (24) | 14 (20) |
| Xylene a | 5 (25) | - | 3 (75) | 11 (44) | 19 (27) |
| 2-heptanone | - | 1 (5) | - | 2 (8) | 3 (4) |
| Styrene a | 2 (10) | 3 (15) | 3 (75) | 6 (24) | 14 (20) |
| Furan methanol | 4 (20) | - | - | 1 (4) | 5 (7) |
| Dimethyl benzene | 1 (5) | 8 (40) | 3 (75) | 12 (48) | 24 (35) |
| Nonanal a | 12 (60) | 3 (15) | 4 (100) | 10 (40) | 29 (42) |
a Identify by comparing the pure standard retention times and mass spectrumin NIST library