R11-1-472. Concentration of radon daughters

When radon daughters concentrations between 0.1 and 0.3 WL are found in an active working area, measurements representative of worker’s breathing zone shall be determined as follows: 1. Where uranium is not mined -- at least three months at random times until concentrations are below 0.1 WL and annually thereafter. 2. Where uranium is mined -- at least every two weeks at random times at all areas where persons work, travel or congregate. If concentrations are found in excess of 0.3 WL in an active working area, radon daughters concentrations shall be determined weekly until such time as the weekly determinations have been 0.3 WL or less for five consecutive weeks. 3. Sample date, locations and results obtained shall be recorded and retained at the mine office for at least two years and shall be made available for inspection.