Index: firmware/App/Controllers/AirTrap.c
===================================================================
diff -u -r14d740bbb065f043daaa348bcda5f447e1c16a32 -r0665a32e26dd466378e6ea6fda940353afc691f1
--- firmware/App/Controllers/AirTrap.c	(.../AirTrap.c)	(revision 14d740bbb065f043daaa348bcda5f447e1c16a32)
+++ firmware/App/Controllers/AirTrap.c	(.../AirTrap.c)	(revision 0665a32e26dd466378e6ea6fda940353afc691f1)
@@ -33,12 +33,12 @@
 
 // ********** private definitions **********
 
-/// Interval (ms/task time) at which the air trap data is published on the CAN bus.
-#define AIR_TRAP_DATA_PUB_INTERVAL          ( MS_PER_SECOND / TASK_GENERAL_INTERVAL )
+
+#define AIR_TRAP_DATA_PUB_INTERVAL          ( MS_PER_SECOND / TASK_GENERAL_INTERVAL )           ///< Interval (ms/task time) at which the air trap data is published on the CAN bus.
+#define AIR_TRAP_FILL_TIMEOUT_MS            ( 6 * MS_PER_SECOND )                               ///< Air trap fill timeout period (in ms).
 #define AIR_PUMP_UPPER_LEVEL_PERSISTENCE    ( 100 / TASK_GENERAL_INTERVAL )                     ///< Persistence time for air pump operation after air trap upper level reads air.
 /// Persistence period for illegal level sensors fault.
 static const U32 AIR_TRAP_ILLEGAL_LEVELS_PERSISTENCE = ( MS_PER_SECOND * 2 / TASK_GENERAL_INTERVAL );
-static const U32 AIR_TRAP_UPPER_LEVEL_PERSISTENCE = ( MS_PER_SECOND * 2 / TASK_GENERAL_INTERVAL );
 
 /// Volume (in mL) of venous portion of blood circuit line.  TODO - get actual volume from Systems.
 #define VENOUS_LINE_VOLUME_ML               ( 200.0F )
@@ -69,7 +69,6 @@
 static U32  fillStartTime = 0;                                                              ///< Time stamp for start of air trap fill.
 
 static U32 airPumpUpperLevelCtr = 0;                                                        ///< Timer count for air pump persistence.
-static U32 airTrapUpperLevelCtr = 0;                                                        ///< Timer count for upper level persistence.
 static U32 airTrapIllegalLevelSensorsCtr = 0;                                               ///< Timer counter for illegal level sensor fault.
 
 // ********** private function prototypes **********
@@ -185,24 +184,11 @@
     airTrapLevels[ AIR_TRAP_LEVEL_SENSOR_LOWER ].data = (U32)( TRUE == lower ? AIR_TRAP_LEVEL_AIR : AIR_TRAP_LEVEL_FLUID );
     airTrapLevels[ AIR_TRAP_LEVEL_SENSOR_UPPER ].data = (U32)( TRUE == upper ? AIR_TRAP_LEVEL_AIR : AIR_TRAP_LEVEL_FLUID );
 
-    if ( ( MODE_TREA == getCurrentOperationMode() ) &&
-         ( AIR_TRAP_LEVEL_FLUID == getAirTrapLevel( AIR_TRAP_LEVEL_SENSOR_UPPER ) ) &&
-         ( AIR_TRAP_VALVE_OPEN_STATE == airTrapControllerState ) )
+    // Clear fill timeout alarm condition if low level sensor sees fluid
+    if ( AIR_TRAP_LEVEL_FLUID == getAirTrapLevel( AIR_TRAP_LEVEL_SENSOR_LOWER ) )
     {
-        if ( ++airTrapUpperLevelCtr >= AIR_TRAP_UPPER_LEVEL_PERSISTENCE )
-        {
-#ifndef _RELEASE_
-            if ( getSoftwareConfigStatus( SW_CONFIG_DISABLE_ILLEGAL_AIR_TRAP_ALARM ) != SW_CONFIG_ENABLE_VALUE )
-#endif
-            {
-                activateAlarmNoData( ALARM_ID_HD_AIR_TRAP_OVERFILL );
-            }
-        }
+        clearAlarmCondition( ALARM_ID_AIR_TRAP_FILL_DURING_TREATMENT );
     }
-    else
-    {
-        airTrapUpperLevelCtr = 0;
-    }
 
     // Check level readings are valid
     if ( ( AIR_TRAP_LEVEL_AIR == getAirTrapLevel( AIR_TRAP_LEVEL_SENSOR_LOWER ) ) &&
@@ -241,10 +227,7 @@
     // Check air trap fill timeout during treatment
     if ( AIR_TRAP_VALVE_OPEN_STATE == airTrapControllerState )
     {
-        F32 bldFlowRate = (F32)getTreatmentParameterU32( TREATMENT_PARAM_BLOOD_FLOW );  // Function will never return zero
-        F32 fillTimeoutMS = ( VENOUS_LINE_VOLUME_ML / bldFlowRate ) * (F32)SEC_PER_MIN * (F32)MS_PER_SECOND;
-
-        if ( TRUE == didTimeout( fillStartTime, fillTimeoutMS ) )
+        if ( TRUE == didTimeout( fillStartTime, AIR_TRAP_FILL_TIMEOUT_MS ) )
         {
 #ifndef _RELEASE_
             if ( getSoftwareConfigStatus( SW_CONFIG_DISABLE_AIR_TRAP_LEVELING_ALARM ) != SW_CONFIG_ENABLE_VALUE )