It should be incubate at 37degree celsius at 30 minutes

37degree centigrade works for us

Fresh HeLa total RNA samples (10 μg) from two biological replicates were incubated at 37°C for 15 min in a final volume of 20 μl in the presence of KCl-containing buffer (final concentrations, 20 mM Tris–HCl (pH 8.0), 0.1 mM MgCl2, and 100 mM KCl) with or without 10 U RNase R