Section 835.403 - Air monitoring(a) Monitoring of airborne radioactivity shall be performed:(1) Where an individual is likely to receive an exposure of 40 or more DAC-hours in a year; or(2) As necessary to characterize the airborne radioactivity hazard where respiratory protective devices for protection against airborne radionuclides have been prescribed.(b) Real-time air monitoring shall be performed as necessary to detect and provide warning of airborne radioactivity concentrations that warrant immediate action to terminate inhalation of airborne radioactive material.63 FR 59683, Nov. 4, 1998