diff --git a/src/ifcgeom/IfcGeom.h b/src/ifcgeom/IfcGeom.h
index 0cf6c0bfd3..540c9fd2ae 100644
--- a/src/ifcgeom/IfcGeom.h
+++ b/src/ifcgeom/IfcGeom.h
@@ -20,6 +20,9 @@
 #ifndef IFCGEOM_H
 #define IFCGEOM_H
 
+#define ALMOST_ZERO (1e-9)
+#define ALMOST_THE_SAME(a,b) (fabs(a-b) < ALMOST_ZERO)
+
 #include <gp_Pnt.hxx>
 #include <gp_Vec.hxx>
 #include <gp_Trsf.hxx>
@@ -41,6 +44,7 @@ namespace IfcGeom {
 	bool convert_face(const IfcUtil::IfcBaseClass* L, TopoDS_Face& result);
 	bool convert_openings(const Ifc2x3::IfcProduct::ptr L, const Ifc2x3::IfcRelVoidsElement::list& openings, TopoDS_Shape& result, const gp_Trsf& trsf);
 	bool profile_helper(int numVerts, float* verts, int numFillets, int* filletIndices, float* filletRadii, gp_Trsf2d trsf, TopoDS_Face& face); 
+	float shape_volume(const TopoDS_Shape& s);
 	namespace Cache {
 		void Purge();
 		void PurgeShapeCache();
diff --git a/src/ifcgeom/IfcGeomFunctions.cpp b/src/ifcgeom/IfcGeomFunctions.cpp
index 556dda313a..4497e9e327 100644
--- a/src/ifcgeom/IfcGeomFunctions.cpp
+++ b/src/ifcgeom/IfcGeomFunctions.cpp
@@ -72,6 +72,9 @@
 
 #include <TopLoc_Location.hxx>
 
+#include <GProp_GProps.hxx>
+#include <BRepGProp.hxx>
+
 #include "../ifcgeom/IfcGeom.h"
 
 bool IfcGeom::convert_openings(const Ifc2x3::IfcProduct::ptr entity, 
@@ -91,7 +94,14 @@ bool IfcGeom::convert_openings(const Ifc2x3::IfcProduct::ptr entity,
 					TopoDS_Shape s;
 					IfcGeom::convert_shape(*it2,s);
 					s.Move(trsf);
+					const float opening_volume = shape_volume(s);
+					if ( opening_volume <= ALMOST_ZERO )
+						Ifc::LogMessage("warning","Empty solid for:",fes->entity);
+					const float original_shape_volume = shape_volume(result);
 					result = BRepAlgoAPI_Cut(result,s);
+					const float volume_after_subtraction = shape_volume(result);
+					if ( ALMOST_THE_SAME(original_shape_volume,volume_after_subtraction) )
+						Ifc::LogMessage("warning","Warning subtraction yields unchanged volume:",entity->entity);
 				}
 			}
 		}
@@ -140,4 +150,9 @@ bool IfcGeom::profile_helper(int numVerts, float* verts, int numFillets, int* fi
 
 	delete[] vertices;
 	return true;
+}
+float IfcGeom::shape_volume(const TopoDS_Shape& s) {
+	GProp_GProps System;
+	BRepGProp::VolumeProperties(s, System);
+	return (float) System.Mass();
 }
\ No newline at end of file
diff --git a/src/ifcgeom/IfcGeomObjects.cpp b/src/ifcgeom/IfcGeomObjects.cpp
index c65555c61f..b2f1d57d22 100644
--- a/src/ifcgeom/IfcGeomObjects.cpp
+++ b/src/ifcgeom/IfcGeomObjects.cpp
@@ -59,7 +59,7 @@ IfcGeomObjects::IfcMesh::IfcMesh(int i, TopoDS_Shape s) {
 		BRepTools::Clean(s);
 		BRepMesh::Mesh(s,0.001f);
 	} catch(...) {
-		Ifc::LogMessage("Error","Failed to triangulate mesh");
+		Ifc::LogMessage("Error","Failed to triangulate mesh:",Ifc::EntityById(i)->entity);
 		return;
 	}
 	TopExp_Explorer exp;
@@ -267,7 +267,7 @@ IfcGeomObjects::IfcGeomObject* _get() {
 					IfcGeom::convert_openings(ifc_product,openings,temp_shape,trsf);
 				}
 			} catch( IfcParse::IfcException& e ) {
-				Ifc::LogMessage("Warning",e.what()); 
+				Ifc::LogMessage("Error",e.what(),ifc_product->entity); 
 			} catch(...) { 
 				Ifc::LogMessage("Error","Error processing openings for:",ifc_product->entity); 
 			}
@@ -357,7 +357,7 @@ bool IfcGeomObjects::Init(const char* fn, bool world_coords) {
 	return IfcGeomObjects::Init(fn, world_coords, 0, 0);
 }
 bool IfcGeomObjects::Init(const char* fn, bool world_coords, std::ostream* log1, std::ostream* log2) {
-	if ( log1 || log2 ) Ifc::SetOutput(log1,log2);
+	Ifc::SetOutput(log1,log2);
 	use_world_coords = world_coords;
 	if ( !Ifc::Init(fn) ) return false;
 
@@ -375,7 +375,7 @@ bool IfcGeomObjects::Init(const char* fn, bool world_coords, std::ostream* log1,
 	return true;
 }
 bool IfcGeomObjects::Init(std::istream& f, int len, bool world_coords, std::ostream* log1, std::ostream* log2) {
-	if ( log1 || log2 ) Ifc::SetOutput(log1,log2);
+	Ifc::SetOutput(log1,log2);
 	use_world_coords = world_coords;
 	if ( !Ifc::Init(f, len) ) return false;
 
@@ -395,3 +395,6 @@ bool IfcGeomObjects::Init(std::istream& f, int len, bool world_coords, std::ostr
 int IfcGeomObjects::Progress() {
 	return 100 * done / total;
 }
+std::string IfcGeomObjects::GetLog() {
+	return Ifc::GetLog();
+}
diff --git a/src/ifcgeom/IfcGeomObjects.h b/src/ifcgeom/IfcGeomObjects.h
index 42169ae500..da60d3f8f6 100644
--- a/src/ifcgeom/IfcGeomObjects.h
+++ b/src/ifcgeom/IfcGeomObjects.h
@@ -113,6 +113,7 @@ namespace IfcGeomObjects {
 	bool Next();	
 	int Progress();
 	const IfcObject* GetObject(int id);
+	std::string GetLog();
 
 }
 
diff --git a/src/ifcgeom/IfcGeomShapes.cpp b/src/ifcgeom/IfcGeomShapes.cpp
index 529f66d2d7..61691d497d 100644
--- a/src/ifcgeom/IfcGeomShapes.cpp
+++ b/src/ifcgeom/IfcGeomShapes.cpp
@@ -125,7 +125,7 @@ bool IfcGeom::convert(const Ifc2x3::IfcPolygonalBoundedHalfSpace::ptr l, TopoDS_
 	TopoDS_Shape halfspace;
 	if ( ! IfcGeom::convert(reinterpret_pointer_cast<Ifc2x3::IfcPolygonalBoundedHalfSpace,Ifc2x3::IfcHalfSpaceSolid>(l),halfspace) ) return false;	
 	TopoDS_Wire wire;
-	if ( ! IfcGeom::convert_wire(l->PolygonalBoundary(),wire) ) return false;	
+	if ( ! IfcGeom::convert_wire(l->PolygonalBoundary(),wire) || ! wire.Closed() ) return false;	
 	gp_Trsf trsf;
 	convert(l->Position(),trsf);
 	TopoDS_Shape extrusion = BRepPrimAPI_MakePrism(BRepBuilderAPI_MakeFace(wire),gp_Vec(0,0,20000.0));
@@ -150,20 +150,30 @@ bool IfcGeom::convert(const Ifc2x3::IfcShellBasedSurfaceModel::ptr l, TopoDS_Sha
 }
 bool IfcGeom::convert(const Ifc2x3::IfcBooleanClippingResult::ptr l, TopoDS_Shape& shape) {
 	TopoDS_Shape s1, s2;
+
 	if ( ! IfcGeom::convert_shape(l->FirstOperand(),s1) )
 		return false;
-	if ( ! IfcGeom::convert_shape(l->SecondOperand(),s2) )
-		return false;
+	
+	const float first_operand_volume = shape_volume(s1);
+	if ( first_operand_volume <= ALMOST_ZERO )
+		Ifc::LogMessage("warning","Empty solid for:",l->FirstOperand()->entity);
+	
+	if (  ! IfcGeom::convert_shape(l->SecondOperand(),s2) ) {
+		shape = s1;
+		Ifc::LogMessage("Error","Failed to convert SecondOperand of:",l->SecondOperand()->entity);
+		return true;
+	}
+
+	const float second_operand_volume = shape_volume(s2);
+	if ( second_operand_volume <= ALMOST_ZERO )
+		Ifc::LogMessage("warning","Empty solid for:",l->SecondOperand()->entity);
+
 	shape = BRepAlgoAPI_Cut(s1,s2);
-	return true;
-}
-bool IfcGeom::convert(const Ifc2x3::IfcClosedShell::ptr l, TopoDS_Shape& shape) {
-	if ( ! IfcGeom::convert((Ifc2x3::IfcConnectedFaceSet::ptr)l,shape) ) return false;
-	try {
-		ShapeFix_Solid solid;
-		solid.LimitTolerance(0.01);
-		shape = solid.SolidFromShell(TopoDS::Shell(shape));
-	} catch(...) {}
+
+	const float volume_after_subtraction = shape_volume(shape);
+	if ( ALMOST_THE_SAME(first_operand_volume,volume_after_subtraction) )
+		Ifc::LogMessage("warning","Warning subtraction yields unchanged volume:",l->entity);
+
 	return true;
 }
 bool IfcGeom::convert(const Ifc2x3::IfcConnectedFaceSet::ptr l, TopoDS_Shape& shape) {
@@ -183,6 +193,11 @@ bool IfcGeom::convert(const Ifc2x3::IfcConnectedFaceSet::ptr l, TopoDS_Shape& sh
 	if ( ! facesAdded ) return false;
 	builder.Perform();
 	shape = builder.SewedShape();
+	try {
+		ShapeFix_Solid solid;
+		solid.LimitTolerance(0.01);
+		shape = solid.SolidFromShell(TopoDS::Shell(shape));
+	} catch(...) {}
 	return true;
 }
 bool IfcGeom::convert(const Ifc2x3::IfcMappedItem::ptr l, TopoDS_Shape& shape) {
diff --git a/src/ifcgeom/IfcGeomWires.cpp b/src/ifcgeom/IfcGeomWires.cpp
index edacb470e4..6d908ffbf6 100644
--- a/src/ifcgeom/IfcGeomWires.cpp
+++ b/src/ifcgeom/IfcGeomWires.cpp
@@ -81,8 +81,8 @@ bool IfcGeom::convert(const Ifc2x3::IfcCompositeCurve::ptr l, TopoDS_Wire& wire)
 		const Ifc2x3::IfcCurve::ptr curve = (*it)->ParentCurve();
 		TopoDS_Wire wire2;
 		if ( ! IfcGeom::convert_wire(curve,wire2) ) continue;
-		ShapeFix_ShapeTolerance FTol;
-		FTol.SetTolerance(wire2, 0.01, TopAbs_WIRE);
+		//ShapeFix_ShapeTolerance FTol;
+		//FTol.SetTolerance(wire2, 0.01, TopAbs_WIRE);
 		w.Add(wire2);
 		if ( w.Error() != BRepBuilderAPI_WireDone ) {
 			Ifc::LogMessage("Error","Failed to join curve segments:",l->entity);
diff --git a/src/ifcgeom/IfcRegister.h b/src/ifcgeom/IfcRegister.h
index be851e1581..b17fc1a583 100644
--- a/src/ifcgeom/IfcRegister.h
+++ b/src/ifcgeom/IfcRegister.h
@@ -39,7 +39,6 @@
 using namespace Ifc2x3;
 
 SHAPE(IfcExtrudedAreaSolid);
-SHAPE(IfcClosedShell);
 SHAPE(IfcConnectedFaceSet);
 SHAPE(IfcFacetedBrep);
 SHAPE(IfcShellBasedSurfaceModel);
diff --git a/src/ifcgeom/IfcRegisterConvertShape.h b/src/ifcgeom/IfcRegisterConvertShape.h
index 0940020a91..9655755d6b 100644
--- a/src/ifcgeom/IfcRegisterConvertShape.h
+++ b/src/ifcgeom/IfcRegisterConvertShape.h
@@ -2,12 +2,13 @@
 #define SHAPE(T) \
 	if ( l->is(T::Class()) ) { \
 		try { \
-			bool b = convert((T*)l,r); \
-			if ( b ) { \
+			if ( convert((T*)l,r) ) { \
 				Cache::Shape[l->entity->id()] = r; \
 				return true; \
-			} else { return false; }\
-		} catch(...) { Ifc::LogMessage("Error","Failed to convert:",l->entity); } \
+			} \
+		} catch(...) {  } \
+		Ifc::LogMessage("Error","Failed to convert:",l->entity); \
+		return false; \
 	}
 #include "IfcRegisterDef.h"
 
diff --git a/src/ifcparse/IfcParse.cpp b/src/ifcparse/IfcParse.cpp
index 7505296eb3..ca7964ffd8 100644
--- a/src/ifcparse/IfcParse.cpp
+++ b/src/ifcparse/IfcParse.cpp
@@ -677,10 +677,11 @@ void Ifc::Dispose() {
 	bytype.clear();
 	byid.clear();
 	byref.clear();
-  file->Close();
+	file->Close();
 	delete file;
 	delete tokens;
 	offsets.clear();
+	log_stream.clear();
 }
 
 float UnitPrefixToValue( Ifc2x3::IfcSIPrefix::IfcSIPrefix v ) {
@@ -702,13 +703,22 @@ float UnitPrefixToValue( Ifc2x3::IfcSIPrefix::IfcSIPrefix v ) {
 	else if ( v == Ifc2x3::IfcSIPrefix::ATTO  ) return (float) 1e-18;
 	else return 1.0f;
 }
-void Ifc::SetOutput(std::ostream* l1, std::ostream* l2) { log1 = l1; log2 = l2; }
+void Ifc::SetOutput(std::ostream* l1, std::ostream* l2) { 
+	log1 = l1; 
+	log2 = l2; 
+	if ( ! log2 ) {
+		log2 = &log_stream;
+	}
+}
 void Ifc::LogMessage(const std::string& type, const std::string& message, const IfcAbstractEntityPtr entity) {
 	if ( log2 ) {
 		(*log2) << "[" << type << "] " << message << std::endl;
 		if ( entity ) (*log2) << entity->toString() << std::endl;
 	}
 }
+std::string Ifc::GetLog() {
+	return log_stream.str();
+}
 
 File* Ifc::file = 0;
 std::ostream* Ifc::log1 = 0;
@@ -722,3 +732,4 @@ MapEntitiesByType Ifc::bytype;
 MapEntityById Ifc::byid;
 MapEntitiesByRef Ifc::byref;
 MapOffsetById Ifc::offsets;
+std::stringstream Ifc::log_stream;
diff --git a/src/ifcparse/IfcParse.h b/src/ifcparse/IfcParse.h
index 6ac14909d7..effeae5bb6 100644
--- a/src/ifcparse/IfcParse.h
+++ b/src/ifcparse/IfcParse.h
@@ -222,6 +222,7 @@ private:
 	static unsigned int lastId;
 	static std::ostream* log1;
 	static std::ostream* log2;
+	static std::stringstream log_stream;
 public:
 	static void SetOutput(std::ostream* l1, std::ostream* l2);
 	static void LogMessage(const std::string& type, const std::string& message, const IfcAbstractEntityPtr entity=0);
@@ -243,6 +244,7 @@ public:
 	static bool Init(const std::string& fn);
 	static bool Init(std::istream& fn, int len);
 	static bool Init(IfcParse::File* f);
+	static std::string GetLog();
 	static void Dispose();
 	static float LengthUnit;
 	static float PlaneAngleUnit;
diff --git a/src/ifcwrap/Interface.h b/src/ifcwrap/Interface.h
index 908592449c..4428bac54c 100644
--- a/src/ifcwrap/Interface.h
+++ b/src/ifcwrap/Interface.h
@@ -47,4 +47,6 @@ namespace IfcGeomObjects {
 	int Progress();
 	const IfcObject* GetObject(int id);
 	bool CleanUp();
+	std::string GetLog();
+
 };
\ No newline at end of file