Index: firmware/App/Modes/Prime.c
===================================================================
diff -u -re2cf7feff54dad3fc5be72619fa64b5421fc6f9f -rcd5be724d5a3ba7457e761191d82f278654d7f5c
--- firmware/App/Modes/Prime.c	(.../Prime.c)	(revision e2cf7feff54dad3fc5be72619fa64b5421fc6f9f)
+++ firmware/App/Modes/Prime.c	(.../Prime.c)	(revision cd5be724d5a3ba7457e761191d82f278654d7f5c)
@@ -1,14 +1,14 @@
 /**************************************************************************
 *
-* Copyright (c) 2020-2023 Diality Inc. - All Rights Reserved.
+* Copyright (c) 2020-2024 Diality Inc. - All Rights Reserved.
 *
 * THIS CODE MAY NOT BE COPIED OR REPRODUCED IN ANY FORM, IN PART OR IN
 * WHOLE, WITHOUT THE EXPLICIT PERMISSION OF THE COPYRIGHT OWNER.
 *
 * @file    Prime.c
 *
-* @author  (last)      Vinayakam Mani
-* @date    (last)      29-Aug-2023
+* @author  (last)      Sean Nash
+* @date    (last)      02-Oct-2023
 *
 * @author  (original)  Quang Nguyen
 * @date    (original)  08-Dec-2020
@@ -40,7 +40,8 @@
 #define MAX_PRIME_TIME                                      ( 30 * SEC_PER_MIN )                               ///< Maximum prime time (in seconds).
 #define PRIME_DATA_PUB_INTERVAL                             ( MS_PER_SECOND / TASK_GENERAL_INTERVAL )          ///< Interval (ms/task time) at which the prime data is published on the CAN bus.
 
-#define BLOOD_PUMP_SLOW_FLOW_RATE_PURGE_AIR_ML_MIN          150                                                ///< Blood pump slow flow rate after fluid reach lower level of air trap sensor.
+#define BLOOD_PUMP_INIT_FLOW_RATE_PURGE_AIR_ML_MIN          150                                                ///< Blood pump initial flow rate before fluid reach upper level of air trap sensor.
+#define BLOOD_PUMP_SLOW_FLOW_RATE_PURGE_AIR_ML_MIN          50                                                 ///< Blood pump slow flow rate for subsequent returns to purge state.
 #define BLOOD_PUMP_SALINE_FLOW_RATE_PURGE_AIR_ML_MIN        200                                                ///< Blood pump very slow flow rate during prime saline dialyzer state
 #define BLOOD_PUMP_SLOW_FLOW_RATE_CIRC_BLOOD_CIRCUIT_ML_MIN 150                                                ///< Blood pump slow flow rate during prime recirculate blood circuit state.
 #define BLOOD_PUMP_FAST_FLOW_RATE_CIRC_BLOOD_CIRCUIT_ML_MIN 300                                                ///< Blood pump fast flow rate during prime recirculate blood circuit state.
@@ -148,7 +149,7 @@
 static void resetPrimeFlags();
 static void setupForPrimePause( void );
 static void broadcastPrimingStatus( void );
-static void purgeAirValvesBloodPumpControl( void );
+static void purgeAirValvesBloodPumpControl( BOOL firstTime );
 static void handlePrimeBubbleClear( void );
 
 static HD_PRE_TREATMENT_PRIME_STATE_T handlePrimeWaitForUserStartState( void );
@@ -459,9 +460,10 @@
  * to purge air.
  * @details Inputs: None
  * @details Outputs: run blood pump, close VDI, VDO, VBA and VBV valves, open VBT valve
- * @return current state (sub-mode)
+ * @param firstTime flag indicating whether this is first time setting up for purge state
+ * @return none
  *************************************************************************/
-static void purgeAirValvesBloodPumpControl( void )
+static void purgeAirValvesBloodPumpControl( BOOL firstTime )
 {
     setValvePosition( VDI, VALVE_POSITION_C_CLOSE );
     setValvePosition( VDO, VALVE_POSITION_C_CLOSE );
@@ -472,9 +474,15 @@
     signalDialOutPumpHardStop();
     signalDialInPumpHardStop();
 
-    // Set the Blood Pump rate to 150 mL/min that helps to avoid entering saline bubbles in to PBo line
-    setBloodPumpTargetFlowRate( BLOOD_PUMP_SLOW_FLOW_RATE_PURGE_AIR_ML_MIN, MOTOR_DIR_FORWARD, PUMP_CONTROL_MODE_OPEN_LOOP );
-
+    // For subsequent returns to blood side purge air state, slow down BP to prevent bubbles from getting up into PBo line
+    if ( TRUE == firstTime )
+    {
+        setBloodPumpTargetFlowRate( BLOOD_PUMP_INIT_FLOW_RATE_PURGE_AIR_ML_MIN, MOTOR_DIR_FORWARD, PUMP_CONTROL_MODE_OPEN_LOOP );
+    }
+    else
+    {
+        setBloodPumpTargetFlowRate( BLOOD_PUMP_SLOW_FLOW_RATE_PURGE_AIR_ML_MIN, MOTOR_DIR_FORWARD, PUMP_CONTROL_MODE_OPEN_LOOP );
+    }
 }
 
 /*********************************************************************//**
@@ -606,7 +614,7 @@
 {
     HD_PRE_TREATMENT_PRIME_STATE_T state = HD_PRIME_SALINE_PURGE_AIR_STATE;
 
-    purgeAirValvesBloodPumpControl();
+    purgeAirValvesBloodPumpControl( TRUE );
     purgeAirTimeOutStartTime = getMSTimerCount();
     primeSalineDialyzerBubbleClearStartTime = getMSTimerCount();
 
@@ -681,14 +689,17 @@
 {
     HD_PRE_TREATMENT_PRIME_STATE_T state = HD_PRIME_SALINE_CIRC_BLOOD_CIRCUIT_STATE;
 
-    if ( AIR_TRAP_LEVEL_AIR == getAirTrapLevel( AIR_TRAP_LEVEL_SENSOR_LOWER ) )
+    if ( ( AIR_TRAP_LEVEL_AIR == getAirTrapLevel( AIR_TRAP_LEVEL_SENSOR_LOWER ) ) &&
+         ( ( BUBBLE_DETECTED == getBubbleStatus( ADV ) ) || ( TRUE == didTimeout( noAirDetectedStartTime, NO_AIR_DETECTED_COUNT ) ) ) )
     {
-        purgeAirValvesBloodPumpControl();
+        signalBloodPumpHardStop();
+        purgeAirValvesBloodPumpControl( FALSE );
         purgeAirTimeOutStartTime = getMSTimerCount();
         state = HD_PRIME_SALINE_PURGE_AIR_STATE;
     }
 
-    if ( TRUE == didTimeout( noAirDetectedStartTime, NO_AIR_DETECTED_COUNT ) )
+    if ( ( TRUE == didTimeout( noAirDetectedStartTime, NO_AIR_DETECTED_COUNT ) ) &&
+         ( AIR_TRAP_LEVEL_FLUID == getAirTrapLevel( AIR_TRAP_LEVEL_SENSOR_LOWER ) ) )
     {
         signalBloodPumpHardStop();
         state = HD_PRIME_RESERVOIR_ONE_FILL_COMPLETE_STATE;