In order to reduce backgrounds from radon-daughter plate-out onto detector surfaces, an ultra-low-radon cleanroom is being commissioned at the South Dakota School of Mines and Technology. An improved vacuum-swing-adsorption radon mitigation system an
d cleanroom build upon a previous design implemented at Syracuse University that achieved radon levels of $sim$0.2$,$Bq$,$m$^{-3}$. This improved system will employ a better pump and larger carbon beds feeding a redesigned cleanroom with an internal HVAC unit and aged water for humidification. With the rebuilt (original) radon mitigation system, the new low-radon cleanroom has already achieved a $>$$,$300$times$ reduction from an input activity of $58.6pm0.7$$,$Bq$,$m$^{-3}$ to a cleanroom activity of $0.13pm0.06$$,$Bq$,$m$^{-3}$.
