I believe it can run fan only. I think it depends on the humidity level inside the room. They make heat-pump and condensing dryers both are installed without a

I believe it can run fan only. I think it depends on the humidity level inside the room. They make heat-pump and condensing dryers both are installed without a vent. I installed 7 condensing dryers in the other apartments. I think the tech specs show that the condensing dryer uses less energy. I also didn't want the heat-pump dryer adding a load to the apartments heat-pump heating system. The fear may have been unwarranted. I'm happy with the condensing dryers.