Index: firmware/App/Controllers/AirTrap.c
===================================================================
diff -u -r62dd464b8b5c6c5cba968ba63aca7c0ed12f445a -rf468c679af3d5192cf860cae99054d5aa784b443
--- firmware/App/Controllers/AirTrap.c	(.../AirTrap.c)	(revision 62dd464b8b5c6c5cba968ba63aca7c0ed12f445a)
+++ firmware/App/Controllers/AirTrap.c	(.../AirTrap.c)	(revision f468c679af3d5192cf860cae99054d5aa784b443)
@@ -80,7 +80,7 @@
 // Air pump on delay after fill adjustment
 static const U32 AIR_PUMP_ON_DELAY_ADJUST_AFTER_FILL = ( AIR_PUMP_ON_DELAY_TIME_MS - ( 1 * MS_PER_SECOND ) );
 
-static BOOL airTrapValveOpenAtStablePressureState = FALSE;                                  ///< Periodic AirTrap fill during pressure stable state, to clear any accumulated bubbles
+static BOOL airTrapValveOpenAtStartOfTreatement = FALSE;                                    ///< To Keep the fluid level high close to Air trap upper level during start of treatment
 
 // ********** private function prototypes **********
 
@@ -102,7 +102,7 @@
 
     resetAirTrap();
     airTrapDataPublicationTimerCounter      = DATA_PUBLISH_COUNTER_START_COUNT;
-    airTrapValveOpenAtStablePressureState   = TRUE;
+    airTrapValveOpenAtStartOfTreatement     = TRUE;
     airPumpOnDelayStartTime                 = getMSTimerCount();
     stopAirPumpStartTime                    = 0;
 
@@ -171,19 +171,6 @@
 
 /*********************************************************************//**
  * @brief
- * The signalAirTrapValveOpen function sets the flag to fill air trap.
- * @details Inputs: none
- * @details Outputs: airTrapValveOpenAtStablePressureState
- * @return none
- *************************************************************************/
-void signalAirTrapPeriodicFill( void )
-{
-    // Open air trap valve
-    airTrapValveOpenAtStablePressureState = TRUE;
-}
-
-/*********************************************************************//**
- * @brief
  * The isAirTrapControlling function determines whether the air trap is
  * currently controlling.
  * @details Inputs: airTrapControllerState
@@ -390,10 +377,10 @@
         }
     }
 
-    //Open valve when requested during pressure stable state
-    else if ( TRUE == airTrapValveOpenAtStablePressureState )
+    //Open valve once at start of treatment ( blood priming)
+    else if ( TRUE == airTrapValveOpenAtStartOfTreatement )
     {
-        airTrapValveOpenAtStablePressureState = FALSE;
+        airTrapValveOpenAtStartOfTreatement = FALSE;
         if ( AIR_PUMP_STATE_ON == getAirPumpState() )
         {
             setAirPumpState( AIR_PUMP_STATE_OFF );
Index: firmware/App/Controllers/AirTrap.h
===================================================================
diff -u -r517905db003e860a4c4a21e9d0ac84e38be2d9ad -rf468c679af3d5192cf860cae99054d5aa784b443
--- firmware/App/Controllers/AirTrap.h	(.../AirTrap.h)	(revision 517905db003e860a4c4a21e9d0ac84e38be2d9ad)
+++ firmware/App/Controllers/AirTrap.h	(.../AirTrap.h)	(revision f468c679af3d5192cf860cae99054d5aa784b443)
@@ -68,7 +68,6 @@
 void startAirTrapControl( void );
 void endAirTrapControl( void );
 BOOL isAirTrapControlling( void );
-void signalAirTrapPeriodicFill( void );
 
 AIR_TRAP_LEVELS_T getAirTrapLevel( AIR_TRAP_LEVEL_SENSORS_T sensor );
 AIR_TRAP_LEVELS_T getRawAirTrapLevel( AIR_TRAP_LEVEL_SENSORS_T sensor );
Index: firmware/App/Controllers/PresOccl.c
===================================================================
diff -u -r517905db003e860a4c4a21e9d0ac84e38be2d9ad -rf468c679af3d5192cf860cae99054d5aa784b443
--- firmware/App/Controllers/PresOccl.c	(.../PresOccl.c)	(revision 517905db003e860a4c4a21e9d0ac84e38be2d9ad)
+++ firmware/App/Controllers/PresOccl.c	(.../PresOccl.c)	(revision f468c679af3d5192cf860cae99054d5aa784b443)
@@ -677,8 +677,6 @@
                 stabilizationStartTimeMs = getMSTimerCount();
                 useShortStabilizeTime = USE_NORMAL_STABILIZATION_PERIOD;
                 currPresLimitsState = PRESSURE_LIMITS_STATE_STABILIZATION;
-                // Fill air trap to clear any accumulated bubbles
-                signalAirTrapPeriodicFill();
             }
             break;