Index: firmware/App/Modes/Rinseback.c
===================================================================
diff -u -r2f9807457197c347c20a24c64492edcf063f3daa -r8d3dbd25627fb7e993409eb47b2575e0430afddd
--- firmware/App/Modes/Rinseback.c	(.../Rinseback.c)	(revision 2f9807457197c347c20a24c64492edcf063f3daa)
+++ firmware/App/Modes/Rinseback.c	(.../Rinseback.c)	(revision 8d3dbd25627fb7e993409eb47b2575e0430afddd)
@@ -82,6 +82,7 @@
 static BOOL recircRequested;                                                ///< Flag indicates user requesting to begin re-circulation (confirming disconnection and shunt).
 static BOOL backToTreatmentRequested;                                       ///< Flag indicates user requesting to go back to treatment (confirming still connected).
 static BOOL endTreatmentRequested;                                          ///< Flag indicates user requesting to end treatment.
+static BOOL airTrapFillInProgress;                                          ///< Flag indicates an air trap fill is in progress.
 
 // ********** private function prototypes **********
 
@@ -133,6 +134,7 @@
     rinsebackAdditionalTimerCtr = 0;
     rinsebackPublishTimerCtr = 0;
     resetRinsebackFlags();
+    airTrapFillInProgress = FALSE;  // set to false initially - so keep after call to reset function
 }
 
 /*********************************************************************//**
@@ -154,6 +156,7 @@
     recircRequested = FALSE;
     backToTreatmentRequested = FALSE;
     endTreatmentRequested = FALSE;
+    airTrapFillInProgress = isAirTrapFillInProgress();
 }
 
 /*********************************************************************//**
@@ -405,8 +408,13 @@
  * @brief
  * The handleRinsebackRunState function handles the rinseback run state
  * operations.
- * @details Inputs: flags
- * @details Outputs: cumulativeRinsebackVolume_mL, flags handled
+ * @details Inputs: endRinsebackRequested, pauseRinsebackRequested,
+ * airTrapFillInProgress, rinsebackRate_mL_min, incrRinsebackFlowRateRequested,
+ * decrRinsebackFlowRateRequested
+ * @details Outputs: cumulativeRinsebackVolume_mL, rinsebackTimerCtr,
+ * targetRinsebackVolumePlusAdditional_mL, rinsebackRate_mL_min,
+ * incrRinsebackFlowRateRequested, decrRinsebackFlowRateRequested,
+ * targetRinsebackVolumePlusAdditional_mL, rinsebackRate_mL_min
  * @return next rinseback state
  *************************************************************************/
 static RINSEBACK_STATE_T handleRinsebackRunState( void )
@@ -453,9 +461,25 @@
         setupForRinsebackStopOrPause();
         result = RINSEBACK_PAUSED_STATE;
     }
+    // if an air trap fill has started, set BP rate and VBV state accordingly
+    else if ( ( airTrapFillInProgress != TRUE ) && ( TRUE == isAirTrapFillInProgress() ) )
+    {
+        // set BP to air trap fill rate if air trap fill has been initiated
+        setBloodPumpTargetFlowRate( AIR_TRAP_FILL_BLOOD_FLOW_RATE, MOTOR_DIR_FORWARD, PUMP_CONTROL_MODE_CLOSED_LOOP );
+        // close VBV for fill
+        setValvePosition( VBV, VALVE_POSITION_C_CLOSE );
+    }
     // Otherwise, continue rinseback
     else
-    {   // Has user requested rate change?
+    {
+        if ( ( TRUE == airTrapFillInProgress ) && ( isAirTrapFillInProgress() != TRUE ) )
+        {
+            // re-open VBV after fill
+            setValvePosition( VBV, VALVE_POSITION_B_OPEN );
+            // restore BP to rinseback blood flow rate
+            setBloodPumpTargetFlowRate( rinsebackRate_mL_min, MOTOR_DIR_FORWARD, PUMP_CONTROL_MODE_CLOSED_LOOP );
+        }
+        // Has user requested rate change?
         if ( ( TRUE == incrRinsebackFlowRateRequested ) || ( TRUE == decrRinsebackFlowRateRequested ) )
         {
             U32 rbRate = rinsebackRate_mL_min;
@@ -576,8 +600,10 @@
  * @brief
  * The handleRinsebackRunAdditionalState function handles the rinseback additional
  * state operations.
- * @details Inputs: flags
- * @details Outputs: flags handled
+ * @details Inputs: additionalRinsebackVolume_mL, rinsebackAdditionalTimerCtr
+ * @details Outputs: rinsebackTimerCtr, additionalRinsebackVolume_mL,
+ * totalAdditionalRinsebackVolume_mL, cumulativeRinsebackVolume_mL,
+ * rinsebackAdditionalTimerCtr
  * @return next rinseback state
  *************************************************************************/
 static RINSEBACK_STATE_T handleRinsebackRunAdditionalState( void )
@@ -629,6 +655,22 @@
             setRinsebackIsCompleted( TRUE );
         }
     }
+    // if an air trap fill has started, set BP rate and VBV state accordingly
+    else if ( ( airTrapFillInProgress != TRUE ) && ( TRUE == isAirTrapFillInProgress() ) )
+    {
+        // set BP to air trap fill rate if air trap fill has been initiated
+        setBloodPumpTargetFlowRate( AIR_TRAP_FILL_BLOOD_FLOW_RATE, MOTOR_DIR_FORWARD, PUMP_CONTROL_MODE_CLOSED_LOOP );
+        // close VBV for fill
+        setValvePosition( VBV, VALVE_POSITION_C_CLOSE );
+    }
+    // re-open VBV and restore BP rate after air trap fill
+    else if ( ( TRUE == airTrapFillInProgress ) && ( isAirTrapFillInProgress() != TRUE ) )
+    {
+        // re-open VBV after fill
+        setValvePosition( VBV, VALVE_POSITION_B_OPEN );
+        // restore BP to rinseback blood flow rate
+        setBloodPumpTargetFlowRate( rinsebackRate_mL_min, MOTOR_DIR_FORWARD, PUMP_CONTROL_MODE_CLOSED_LOOP );
+    }
 
     return result;
 }