RADEX non-LTE modeling of the relation between the kinetic temperature and the average ratio of para-H₂CO 3₂₂–2₂₁/3₀₃–2₀₂ and 3₂₁–2₂₀/3₀₃–2₀₂ with an assumed density of n(H₂) = 10⁵ cm^-3, an averaged linewidth of 2.0 km s^-1, and column density of N(para-H₂CO) = 1 × 10¹³ (red line), 5 × 10¹³ (green line), and 1 × 10¹⁴ cm^-2 (blue line). The black points are derived from our observed H₂CO line ratios for a column density N(para-H₂CO) = 5 × 10¹³ cm^-2, the average value for the OMC-1 (see Sect. 3.2). The temperature uncertainties are obtained from observed para-H₂CO line ratio errors.