  A potential background for the SuperCDMS SNOLAB dark matter experiment is
from radon daughters that have plated out onto detector surfaces. To reach
desired backgrounds, understanding plate-out rates during detector fabrication
as well as mitigating radon in surrounding air is critical. A radon mitigated
cleanroom planned at SNOLAB builds upon a system commissioned at the South
Dakota School of Mines & Technology (SD Mines). The ultra-low radon cleanroom
at SD Mines has air supplied by a vacuum-swing-adsorption radon mitigation
system that has achieved $>$1000$\times$ reduction for a cleanroom activity
consistent with zero and $<0.067\,$Bq$\,$m$^{-3}$ at 90% confidence. Our
simulation of this system, validated against calibration data, provides
opportunity for increased understanding and optimization for this and future
systems.
