Dust SED for G₀ = 1 in the region (R [kpc], z [kpc]) = (14, 0) in the galaxy NGC 891 for an assumed column density N_H = 10²⁰ cm^-2. The red and blue lines represent the SED due to photon heating only, with (blue line) and without (red line) the size limitation at a_min = 2 nm caused by the presence of a gas at T_gas = 10⁷ K and n_H = 10^-3 cm^-3. Black lines represent the various contribution to the SED shown by the red line.