Index: firmware/App/Controllers/PresOccl.c
===================================================================
diff -u -rf7b149d8b8c9ea6ac58e4739101693d251d7a355 -r27f3db92495948d4c1192421c1b0c20338c4a034
--- firmware/App/Controllers/PresOccl.c	(.../PresOccl.c)	(revision f7b149d8b8c9ea6ac58e4739101693d251d7a355)
+++ firmware/App/Controllers/PresOccl.c	(.../PresOccl.c)	(revision 27f3db92495948d4c1192421c1b0c20338c4a034)
@@ -57,11 +57,13 @@
 #define VENOUS_PRESSURE_STALE_DATA          2                                               ///< Venous pressure status bits indicate data is stale (no new data since last fpga read).
 #define VENOUS_PRESSURE_DIAG_CONDITION      3                                               ///< Venous pressure status bits diagnostic condition (alarm).
 
-#define MAX_TIME_BETWEEN_VENOUS_READINGS    ( 500 / TASK_GENERAL_INTERVAL )                 ///< Maximum time without fresh inline venous pressure reading.
+static const U32 MAX_TIME_BETWEEN_VENOUS_READINGS = ( 500 / TASK_GENERAL_INTERVAL );        ///< Maximum time without fresh inline venous pressure reading.
 
 #define OCCLUSION_THRESHOLD                 25000                                           ///< Threshold above which an occlusion is detected.
 #define CARTRIDGE_LOADED_THRESHOLD          5000                                            ///< Threshold above which a cartridge is considered loaded.
 
+#define EMPTY_SALINE_BAG_THRESHOLD_MMHG     -300.0                                          ///< Threshold below which the saline bag is considered empty (in mmHg).  TODO - get real threshold from Systems
+static const U32 EMPTY_SALINE_BAG_PERSISTENCE = ( 250 / TASK_GENERAL_INTERVAL );            ///< Time that saline bag looks empty before saying it is empty.  TODO - use persistent alarm when updated
 /// Occlusion sensors minimum pressure reading limit when no cartridge is loaded.
 #define OCCLUSION_NO_CARTRIDGE_PRESSURE_READING_MIN             2000
 /// Occlusion sensors maximum pressure reading limit when cartridge is considered loaded.
@@ -100,6 +102,7 @@
 static OVERRIDE_U32_T dialOutPumpOcclusion = {0, 0, 0, 0 };                     ///< Measured dialysate outlet pump occlusion pressure.
 
 static U32 staleVenousPressureCtr = 0;                                          ///< Timer counter for stale venous pressure reading.
+static U32 emptySalineBagCtr = 0;                                               ///< Timer counter for empty bag detection.
 
 // ********** private function prototypes **********
 
@@ -154,6 +157,35 @@
     return result;
 }
 
+/*********************************************************************//**
+ * @brief
+ * The isSalineBagEmpty function determines whether the saline bag is empty.
+ * It is assumed that this function will only be called from mode handling
+ * (General Task) when pumping (BP) from the saline bag.
+ * Determination is based on pressure going below a negative threshold.
+ * @details Inputs: arterial line pressure
+ * @details Outputs: none
+ * @return TRUE if arterial line pressure is below threshold, FALSE if not.
+ *************************************************************************/
+BOOL isSalineBagEmpty( void )
+{
+    BOOL result = FALSE;
+
+    if ( getMeasuredArterialPressure() < EMPTY_SALINE_BAG_THRESHOLD_MMHG )
+    {
+        if ( ++emptySalineBagCtr >= EMPTY_SALINE_BAG_PERSISTENCE )
+        {
+            result = TRUE;
+        }
+    }
+    else
+    {
+        emptySalineBagCtr = 0;
+    }
+
+    return result;
+}
+
 /*********************************************************************//**
  * @brief
  * The execPresOccl function executes the pressure and occlusion monitor.