Observed (histogram) and simulated spectra (lines) of selected SO₂ transitions in the central region of the remnant. The simulations include the best LTE model (dashed; T_ex = 7.7 K and N = 8.3 × 10¹⁵ cm⁻²), the best RADEX model with collisional rates of ortho and para H₂ (solid; T_kin = 10.7 K and N = 5.4 × 10¹⁵ cm⁻²), and the best RADEX model with collisional rates of H₂ scaled from calculations of collisions with He (dashed-dotted; T_kin = 19.4 K and N = 5.1 × 10¹⁵ cm⁻²). Since both collision partners are abundant in CK Vul, we are not able to indicate which of the two models is more adequate. This illustrates one of limitations of the non-LTE excitation analysis. Column densities are given for a beam filling factor of 0.41. Main species whose lines are contaminating the spectra of SO₂ are indicated. Panels are ordered with increasing E_u from left to right and from top to bottom.