Hello Radsafers Can anyone out there give me information and feedback on their experiences with the E-Perm (sp?) radon detector system. We're considering it for use to measure Rn-220 and Rn-222 and to replace track etch detectors. Thanks in advance. Kelly Grahn Illinois Dept of Nuclear Safety West Chicago Field Office grahnk@aol.com or grahn@idns.state.il.us