IEC 60079 Hazardous Area Codes

Gas groups, temperature classes, zone definitions, and equipment protection level (EPL) mapping per IEC 60079 series.

Zone Classifications

IEC Zone	NEC/CEC Equivalent	Definition (IEC 60079-10-1)	Typical Example	Reference
Zone 0	Class I Div 1 (continuous)	Explosive gas atmosphere is present continuously or for long periods	Inside fuel tank vapor space	IEC 60079-10-1:2020 Sec 6
Zone 1	Class I Div 1 (intermittent)	Explosive gas atmosphere is likely to occur in normal operation occasionally	Around vents, sample points, pump seals	IEC 60079-10-1:2020 Sec 6
Zone 2	Class I Div 2	Explosive gas atmosphere is not likely to occur in normal operation; if it does, only briefly	General process areas with closed equipment	IEC 60079-10-1:2020 Sec 6
Zone 20	Class II Div 1 (continuous)	Combustible dust is present continuously or for long periods	Interior of dust collector, hopper	IEC 60079-10-2:2015
Zone 21	Class II Div 1 (intermittent)	Combustible dust is likely to occur in normal operation occasionally	Adjacent to dust filter charge points	IEC 60079-10-2:2015
Zone 22	Class II Div 2	Combustible dust is not likely to occur in normal operation	General areas around dust-handling equipment	IEC 60079-10-2:2015

Gas Groups

IEC Group	NEC Group	Representative Gas	MESG (mm)	MIC Ratio	Reference
IIA	D	Methane / Propane	>0.90	>0.80	IEC 60079-20-1:2017
IIB	C	Ethylene	0.50-0.90	0.45-0.80	IEC 60079-20-1:2017
IIB+H2	C+H2	Hydrogen-mix special	as IIB	as IIB	IEC 60079-20-1:2017
IIC	A/B	Hydrogen / Acetylene	<0.50	<0.45	IEC 60079-20-1:2017
I	MSHA	Methane (mining)	for mining apps	-	IEC 60079-0:2017
IIIA	E (fibers)	Combustible flyings	-	-	IEC 60079-0:2017
IIIB	F (dust)	Non-conductive dust	-	-	IEC 60079-0:2017
IIIC	G (dust)	Conductive dust	-	-	IEC 60079-0:2017

Temperature Classes

T-Class	Max Surface Temp deg C	Max Surface Temp deg F	Note	Reference
T1	450	842	Most flexible; covers most hydrocarbons	IEC 60079-0:2017
T2	300	572	Below H2 AIT; many service fluids	IEC 60079-0:2017
T3	200	392	Below diesel AIT (~210C)	IEC 60079-0:2017
T4	135	275	Below H2S AIT (~270C); below ether AIT	IEC 60079-0:2017
T5	100	212	Specialty - low-AIT solvents	IEC 60079-0:2017
T6	85	185	CS2 / very low AIT services	IEC 60079-0:2017

Protection Methods

Code	Method Name	IEC Standard	Permissible Zones	Description
Ex d	Flameproof enclosure	IEC 60079-1	1, 2	Contains internal explosion; flame-resistant joints
Ex e	Increased safety	IEC 60079-7	1, 2	No arcing/sparking parts; higher creepage and clearance
Ex i	Intrinsic safety	IEC 60079-11	0 (ia), 1 (ib), 2 (ic)	Energy/temperature limited; safest for instruments
Ex p	Pressurized enclosure	IEC 60079-2	1 (px), 2 (py/pz)	Inert gas purge maintains positive pressure
Ex m	Encapsulation	IEC 60079-18	0 (ma), 1 (mb), 2 (mc)	Components encased in compound
Ex n	Non-incendive	IEC 60079-15	2	Non-sparking, restricted breathing
Ex o	Oil immersion	IEC 60079-6	2	Components submerged in oil
Ex q	Powder filling	IEC 60079-5	2	Sand-filled enclosure
Ex t	Dust ignition protection	IEC 60079-31	20 (ta), 21 (tb), 22 (tc)	Dust-tight enclosure with limited surface temp
Ex op	Optical radiation	IEC 60079-28	0 (op is), 1 (op pr), 2 (op sh)	Inherently safe / protected / shielded optical

Notes

Source: IEC_60079_Hazardous_Area_Codes_v1.xlsx

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