                 if (concept = @collection.get(facet.get('concept')))
                     @addColumn(concept, false)
 
+        isConceptUnselected: (concept) ->
+            for facet in @view.facets.models
+                if facet.attributes.concept == concept.id
+                    return false
+
+            return true
+
         addColumn: (concept, add=true) ->
             @available.currentView.find(concept)?.disable()
 
-            if add
+            if add and @isConceptUnselected(concept)
                 facet = new @view.facets.model
                     concept: concept.id
                 @view.facets.add(facet)


        itemView: AvailableItem


    class AvailableGroup extends index.ConceptGroup
        template: templates.availableGroup

        itemView: AvailableSection


    class AvailableColumns extends index.ConceptIndex

        template: templates.available

        events:
            'click .column-item-button': 'triggerAdd'

        triggerAdd: (event) ->
            event.preventDefault()
