  Radon emanation was projected to account for $>50$% of the electron recoil
background in the WIMP region of interest for the LUX-ZEPLIN (LZ) experiment.
To mitigate the amount of radon inside the detector volume, materials with
inherently low radioactivity content were selected for LZ construction through
an extensive screening campaign. The SD Mines radon emanation system was one of
four emanation facilities utilized to screen materials during construction of
LZ. SD Mines also employed a portable radon collection system for equipment too
large or delicate to move to a radon emanation facility. This portable system
was used to assay the Inner Cryostat Vessel in-situ at various stages of
detector construction, resulting in the inference that the titanium cryostat is
the source of significant radon emanation. Assays of a $^{228}$Th source
confirmed that its $^{222}$Rn emanation is low enough for it to be used, and
that 14% of the $^{220}$Rn emanates from the source at room temperature.
