Balmer decrement, Hα/Hβ, plotted against redshift for our sample of 51 galaxies. The points are colour-coded by their corresponding Hα S/N. The error bars combine the random measurement uncertainties on the line fluxes with a systematic uncertainty of 10%. Three lower limits are shown as grey triangles. The horizontal dashed grey line corresponds to a Balmer decrement of 2.86, appropriate for local star-forming regions. The grey shaded region represents the 6% range of Hα/Hβ, corresponding to 5000 < T_e < 30 000 K and 10 < n_e < 500 cm⁻³. The horizontal dotted grey line corresponds to a Balmer decrement of 2.75.