What does Ex d IIB T4 mean?

Ex = explosion protected. d = flameproof enclosure (IEC 60079-1). IIB = Gas Group IIB (e.g. ethylene). T4 = Temperature Class T4 (max surface temp 135°C). This equipment is suitable for Zone 1 and Zone 2 hazardous areas.

What are the main Ex protection types?

Common types: d = flameproof, e = increased safety, i = intrinsic safety (ia/ib/ic), p = pressurized, n = non-sparking, m = encapsulation, o = oil immersion, q = powder filling, t = protection by enclosure (dust).

What are gas groups I, IIA, IIB, IIC?

Group I = Mining (methane). Group IIA = Propane, acetone, etc. Group IIB = Ethylene, hydrogen sulfide. Group IIC = Hydrogen, acetylene, carbon disulfide. IIC is the most stringent — equipment rated IIC can be used in IIA and IIB.

What are temperature classes T1 to T6?

Temperature classes define the max surface temperature: T1=450°C, T2=300°C, T3=200°C, T4=135°C, T5=100°C, T6=85°C. The class must be lower than the auto-ignition temperature of the gas present.

What is Equipment Protection Level (EPL)?

EPL indicates the level of protection: Ga/Da = very high (Zone 0/20), Gb/Db = high (Zone 1/21), Gc/Dc = enhanced (Zone 2/22). 'G' is for gas, 'D' is for dust. EPL was introduced in IEC 60079-0 Edition 6.

Free Engineering Tool

Ex Marking Decoder

Enter any IEC 60079 / ATEX Ex marking string to decode protection type, gas group, temperature class, EPL, and zone suitability.

IEC 60079ATEXZone 0/1/2

Decoded Marking

Protection Types

Code	Method	IEC Standard	Typical Zone
d	Flameproof enclosure	IEC 60079-1	Zone 1, 2
e	Increased safety	IEC 60079-7	Zone 1, 2
ia	Intrinsic safety (level a)	IEC 60079-11	Zone 0, 1, 2
ib	Intrinsic safety (level b)	IEC 60079-11	Zone 1, 2
ic	Intrinsic safety (level c)	IEC 60079-11	Zone 2
p/px/py/pz	Pressurized enclosure	IEC 60079-2	Zone 1, 2
m/ma/mb	Encapsulation	IEC 60079-18	Zone 0, 1, 2
nA/nC/nR	Non-sparking / Type n	IEC 60079-15	Zone 2
o	Oil immersion	IEC 60079-6	Zone 1, 2
q	Powder filling	IEC 60079-5	Zone 1, 2
t/ta/tb/tc	Protection by enclosure (dust)	IEC 60079-31	Zone 20/21/22

Temperature Classes

Class	Max Surface Temp (°C)	Typical Gases
T1	450	Hydrogen, methane, propane
T2	300	Ethanol, butane, acetone
T3	200	Gasoline, hydrogen sulfide, diesel
T4	135	Acetaldehyde, diethyl ether
T5	100	—
T6	85	Carbon disulfide

Ex Marking Decoder | IEC 60079 | ATEX Explosion Protection

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026

Decoded Marking

Protection Types

Temperature Classes