Another essential element in testing is the burn test. This examines the fabric's burn behaviour, its flammability and how easily the flames spread. The position of the material (e.g. horizontal for carpets, vertical for curtains) and source of ignition (e.g. cigarette, Bunsen burner, match, etc.) are varied depending on where the textile is to be used. The smoke produced by the fabric and any toxic gases it contains can also be examined during the burn test.