diff --git a/CODE/stepping.cc b/CODE/stepping.cc
index 35587eb90f74a05947d8830ab77213aa31fc1768..6b98846ad29d3584df11c6ad92c0a96b5fe84c20 100644
--- a/CODE/stepping.cc
+++ b/CODE/stepping.cc
@@ -18,7 +18,7 @@ void MySteppingAction :: UserSteppingAction(const G4Step* step)
         
         G4ThreeVector position = step->GetPreStepPoint()->GetPosition();
 
-        G4double distanceThreshold = 1200.*m;
+        G4double distanceThreshold = -400.*m;  // Punto de deteccion, debe coincidir con la interfaz de las capas de la atmosfera (-1600 (sea level) ,-1200,-800,-400,0,400,800,1200,1600,2000)
 
         // Verifica si la distancia recorrida supera el umbral
         if (position.z() == distanceThreshold)