RMS-MF 2018 with 12/20 Addenda

Companion Guidance—Section C AARST Informational CG 4 Companion Guidance RMS- MF 2018 Heating, Cooling and Ventilation Systems Group 3: Variable Air Distribution The normal operation of these systems can cause changes in distribution of radon or ventilation air and can also affect pressure relationships that can enhance or diminish radon entry. Depending upon the open or closed operating conditions for supply vents and returns vents, radon concentrations can vary widely from test to test (or room to room). Variable Air Distribution: Systems where the airflow from a single air handler is distributed to multiple rooms or locations with independent controls within each room for duct dampering. Such systems include Variable Air Volume (VAV) systems or systems with fixed volume return vents in each room and controls for dampering supply air. Group 4: Variable Outdoor Air Ventilation The normal operation of these systems can cause varying changes in fresh air ventilation that can dilute radon concentrations and also affect pressure relationships that can enhance or diminish radon entry. Depending upon the extent of open or closed intake dampers for outdoor air, radon concentrations can vary widely from test to test or room to room. Outdoor Air Ventilation ( HVAC ): Some schools and large buildings have heating, ventilating and air conditioning ( HVAC ) systems that add fresh air ventilation to the building. Such systems may exist for service to a whole building, multiple rooms or as single unit ventilators. Radon concentrations can vary widely from test to test based the volume of fresh air supplied to room at any given time.