NH₂D/NH₃ deuterium fractionation ratio versus NH₃ column density. Orange marks denote the dense core sample from a low-mass star forming region of Galloway-Sprietsma et al. (2022), blue marks the low-mass sample from a high-mass protocluster in Li et al. (2021), green marks the pre-protostellar cores of a UCHII region in Busquet et al. (2010), red marks the high-mass ATLASGAL clumps of Wienen et al. (2021), and light blue marks with a black outline denote the NH₂D cores (squares) and the NH₃ cores (stars) from the pre-protoclusters in Pillai et al. (2011). Our sample is depicted by black crosses, showing the estimates for NH₃ column density. The downward arrows mark upper limits for the values depicted. Regarding the sample of Wienen et al. (2021), the rounding of values in the CDS table provided by the authors result in many sources having the exact same values.