Abundance of NH₃ (upper panels), HCN (middle panels), and CS (lower panels) relative to H₂ throughout a one-component O-rich outflow with different mass-loss rates Ṁ and clump volume filling factors f_vol. Solid black line: calculated abundance for a smooth, uniform outflow. Solid coloured line: characteristic clump scale l_* = 5 × 10¹² cm, porosity length h_* = 1 × 10¹⁴, 2.5 × 10¹³, 1.25 × 10¹³ cm for f_vol = 0.05, 0.2, 0.4, respectively. Dashed coloured line: l_* = 10¹³ cm, h_* = 2 × 10¹⁴, 5 × 10¹³,  2.5 × 10¹³ cm for f_vol = 0.05, 0.2, 0.4, respectively. Dotted coloured line: l_* = 5 × 10¹³ cm, h_* = 1 × 10¹⁵, 2.5 × 10¹⁴, 1.25 × 10¹⁴ cm for f_vol = 0.05, 0.2, 0.4, respectively.We note that models with f_vol = 0.2,  l_* = 5 × 10¹² cm (green, solid) and f_vol = 0.4,  l_* = 1 × 10¹³ cm (red, dashed) have the same porosity length h_* = 2.5 × 10¹³ cm. For reference, 1 R_* = 5 × 10¹³ cm.