Index: firmware/App/Modes/TreatmentEnd.c
===================================================================
diff -u -r89f4c7f0995e2094b3f26fc7e7e12371e847abac -r6b870cd0699bb3ee22b93981d51373a6c2d56162
--- firmware/App/Modes/TreatmentEnd.c	(.../TreatmentEnd.c)	(revision 89f4c7f0995e2094b3f26fc7e7e12371e847abac)
+++ firmware/App/Modes/TreatmentEnd.c	(.../TreatmentEnd.c)	(revision 6b870cd0699bb3ee22b93981d51373a6c2d56162)
@@ -37,13 +37,17 @@
 #define TX_END_BP_FLOW_RATE_ML_MIN         100
 
 /// Max time to wait for user to initiate final rinseback.
-#define TX_END_TIMEOUT_MS                  ( ( 15 * 60 * MS_PER_SECOND ) / TASK_GENERAL_INTERVAL )  // TODO - get time from Systems
+static const U32 TX_END_TIMEOUT_MS      = ( ( 15 * 60 * MS_PER_SECOND ) / TASK_GENERAL_INTERVAL );  // TODO - get time from Systems
 
+/// Maximum time in this mode before blood sitting warning given (in general task intervals).
+static const U32 MAX_TIME_BLOOD_SITTING = ( ( 5 * SEC_PER_MIN * MS_PER_SECOND ) / TASK_GENERAL_INTERVAL );
+
 // ********** private data **********
 
 static TREATMENT_END_STATE_T treatmentEndState;                             ///< Current state of the treatment end sub-mode.
 
 static U32  txEndTimerCtr;                                                  ///< Timer counter (in GP task intervals) counts time spent waiting for user to initiate final rinseback.
+static U32  bloodSittingTimerCtr;                                           ///< Timer counter tracks time in paused state while blood is sitting.
 
 static BOOL txEndAlarmResumeRequested;                                      ///< Flag indicates user requesting resume from alarm.
 static BOOL txEndAlarmRinsebackRequested;                                   ///< Flag indicates user requesting rinseback from alarm.
@@ -74,6 +78,7 @@
 {
     treatmentEndState = TREATMENT_END_WAIT_FOR_RINSEBACK_STATE;
     txEndTimerCtr = 0;
+    bloodSittingTimerCtr = 0;
     resetTreatmentEndFlags();
 }
 
@@ -139,6 +144,7 @@
     setValvePosition( VBV, VALVE_POSITION_B_OPEN );
     // Start blood pump at Tx End slow flow rate
     setBloodPumpTargetFlowRate( TX_END_BP_FLOW_RATE_ML_MIN, MOTOR_DIR_FORWARD, PUMP_CONTROL_MODE_CLOSED_LOOP );
+    bloodSittingTimerCtr = 0;
     // Start air trap leveling control
     startAirTrapControl();
 }
@@ -238,6 +244,8 @@
 {
     TREATMENT_END_STATE_T result = TREATMENT_END_PAUSED_STATE;
 
+    bloodSittingTimerCtr++;
+
     // Is final rinseback requested?
     if ( ( TRUE == txEndRinsebackRequested ) || ( TRUE == txEndAlarmRinsebackRequested ) )
     {
@@ -254,6 +262,14 @@
     {
         signalEndTreatment();
     }
+    else
+    {
+        // Ensure we do not sit in stopped state for too long
+        if ( bloodSittingTimerCtr > MAX_TIME_BLOOD_SITTING )
+        {
+            activateAlarmNoData( ALARM_ID_BLOOD_SITTING_TOO_LONG_NO_RINSEBACK );
+        }
+    }
 
     return result;
 }