It depends on the technique, application, directive, and used materials. As an example, the connection cable could be heated by the resistor, and therefore the temperature limit is the maximum temperature of the cable. Ceramic wirewound resistors typically have a maximum of 350°C. Aluminium housed types are limited to a maximum of 375°C to comply with UL norm 0508. Steel tube or steel grid types are limited to a temperature of the active elements of 500-650°C