Temperature classification (also known as temperature class, T-class, or T-code) defines the maximum surface temperature that a product destined for use in a potentially hazardous atmosphere is allowed to operate at, relative to an ambient temperature of -20°C to +40°C. Temperature classifications or ratings vary between T1 and T6. TEMPERATURE CLASSI°FICATION* MAX.SUR°FACETEMPERATURE NEC 500/CEC NEC 505/IEC-GROUP II 450°C(842°F) T1 T1 300°C(572°F) T2 T2 280°C(536°F) T2A 260°C(500°F) T2B 230°C(446°F) T2C 215°C(419°F) T2D 200°C(392°F) T3 T3 180°C(356°F) T3A 165°C(329°F) T3B 160°C(320°F) T3C 135°C(275°F) T4 T4 120°C(248°F) T4A 100°C(212°F) T5 T5 85°C(185°F) T6 T6 For example, a rating of T5 means that the maximum temperature of equipment can be up to 100°C while a T4 rating would mean that the maximum surface temperature generated by equipment at room temperature cannot exceed 135°C. The Temperature Class is related to the auto-ignition temperature of the hazardous material. The auto-ignition temperature of a substance is the lowest temperature at which it spontaneously ignites. Some examples of auto-ignition temperatures include: GASSES AUTO-IGNITIONTEMPERATURE INC Hydrogen 560°C Ethylene 425°C Diesel 240°C Diethyl Ether 160°C Carbon Disulphide 95°C
