diff --git a/lib/edit/attachmentsStore.js b/lib/edit/attachmentsStore.js
index 685fddb..1cf1d42 100644
--- a/lib/edit/attachmentsStore.js
+++ b/lib/edit/attachmentsStore.js
@@ -161,11 +161,13 @@ define([], function()
 			var index = objectStore.index("featureId");
 			var keyRange = IDBKeyRange.only(featureId);
 			var deletedCount = 0;
-			index.openKeyCursor(keyRange).onsuccess = function(evt)
+			index.openCursor(keyRange).onsuccess = function(evt)
 			{
 				var cursor = evt.target.result;
 				if(cursor)
 				{
+                    var attachment = cursor.value;
+                    this._revokeLocalURL(attachment);
 					objectStore.delete(cursor.primaryKey);
 					deletedCount++;
 					cursor.continue();
@@ -174,41 +176,62 @@ define([], function()
 				{
 					callback(deletedCount);
 				}
-			};
+			}.bind(this);
 		};
 
 		this.delete = function(attachmentId, callback)
 		{
             console.assert(this._db !== null, "indexeddb not initialized");
 
-            var request = this._db.transaction([OBJECT_STORE_NAME],"readwrite")
-                .objectStore(OBJECT_STORE_NAME)
-                .delete(attachmentId);
-            request.onsuccess = function(event)
+            // before deleting an attachment we must revoke the blob URL that it contains
+            // in order to free memory in the browser
+            this.retrieve(attachmentId, function(success, attachment)
             {
-                setTimeout(function(){callback(true);},1);
-            };
-            request.onerror = function(err)
-            {
-                callback(false,err);
-            };
+                if( !success )
+                {
+                    callback(false,"attachment " + attachmentId + " not found");
+                    return;
+                }
+
+                this._revokeLocalURL(attachment);
+
+                var request = this._db.transaction([OBJECT_STORE_NAME],"readwrite")
+                    .objectStore(OBJECT_STORE_NAME)
+                    .delete(attachmentId);
+                request.onsuccess = function(event)
+                {
+                    setTimeout(function(){callback(true);},1);
+                };
+                request.onerror = function(err)
+                {
+                    callback(false,err);
+                };
+            }.bind(this));
 		};
 
         this.deleteAll = function(callback)
         {
             console.assert(this._db !== null, "indexeddb not initialized");
 
-            var request = this._db.transaction([OBJECT_STORE_NAME],"readwrite")
-                .objectStore(OBJECT_STORE_NAME)
-                .clear();
-            request.onsuccess = function(event)
+            this.getAllAttachments(function(attachments)
             {
-                callback(true);
-            };
-            request.onerror = function(err)
-            {
-                callback(false,err);
-            };
+                attachments.forEach(function(attachment)
+                {
+                    this._revokeLocalURL(attachment);
+                },this);
+
+                var request = this._db.transaction([OBJECT_STORE_NAME],"readwrite")
+                    .objectStore(OBJECT_STORE_NAME)
+                    .clear();
+                request.onsuccess = function(event)
+                {
+                    callback(true);
+                };
+                request.onerror = function(err)
+                {
+                    callback(false,err);
+                };
+            }.bind(this));
         };
 
         this.replaceFeatureId = function(featureLayerUrl, oldId, newId, callback)
@@ -277,6 +300,18 @@ define([], function()
             };
         };
 
+        // internal methods
+
+        this._createLocalURL = function(attachment)
+        {
+
+        };
+
+        this._revokeLocalURL = function(attachment)
+        {
+            window.URL.revokeObjectURL(attachment.url);
+        };
+
 		this.init = function(callback)
 		{
 			console.log("init AttachmentStore");