A and B: Comparison of VOCs concentrations present at lower level in the headspace of cell culture (CALU-1) solution (blue columns) as compared with medium only (red columns) after 4 h (Fig. 4A) and 18 h (Fig. 4B) of incubation. Presented are average concentrations (n = 4 for 4 h of incubation, n = 3 for 18 h of incubation) with standard deviation. Significant differences are labeled with asterisks.