Fractional abundance for B3 fast warm-up (from 10 to 500 K) model at a density of 10⁷ cm⁻³ for the time period 20 000–35 000 yr with the fiducial model. Oxygen-bearing species are shown to the left and nitrogen bearing to the right. The y-axes have different scales. All species are shown in the key with color-coded dashed horizontal lines showing the observed abundances for B3. The thinner dashed lines indicate the upper limit for HC₃ N and the lower limit for C₂H₅CN, as they are the species that best constrain the time span. The black ellipse highlights the difference between the modeled abundance of C₂H₅CN and the lower limit of the observed abundance. At the higher densities we tested, the model abundance of C₂ H₅CN is lower.