When protected by compacted mineral insulation and appropriate outer sheath, Type B is usable from 871 to 1704°C, (1600 to 3100°F). Also easily contaminated, and damaged by reducing atmospheres. The same protective measures as shown above apply to type B Thermocouples. - See more at: http://www.thermometricscorp.com/thermocouple.html#sthash.QqqZhn1f.dpuf