2631417 EERC equilibrium equivalent radon concentration 8 2631421 EERC Energy & Environmental Research Center 2 2631420 EERC Environmental Research Center 2 2631419 EERC Effective Equilibrium Radon Concentration 1 2631423 EERC engage, reflect, and carefully match 1 2631418 EERC equivalent concentration for radon 1 2631422 EERC Estimated equivalent radiation conditions 1