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Explosion Proof Speakers & Intercoms: Guide 2026

Explosion Proof Speakers & Intercoms: Guide 2026
2026-01-04 Author: Aaron Page view: 490
In the industrial field, especially in oil refineries and chemical plants, we often hear the term "explosion proof," but what exactly is it? And what are the different levels of explosion protection? Today, we'll break down explosion proof knowledge from basic definitions to practical applications, helping you easily understand it.

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What is an explosion proof?

Explosion proof refers to controlling the three necessary conditions for an explosion (flammable substances, oxygen, and ignition source) through technical means, ultimately avoiding explosion accidents or limiting the harm caused by explosions.

How are explosion proof zones defined?

Hazardous areas are classified into explosive gas atmosphere and flammable dust atmosphere based on the physical state of the substances present. Furthermore, based on the duration of the presence of hazardous substances in the areas, hazardous areas in two different physical states are divided into three zones.Explosive gas atmospheres are classified into Zone 0, Zone 1, and Zone 2.
  • Zone 0: Areas where explosive gas atmospheres are continuously present, exist for extended periods, or occur frequently.
  • Zone 1: Areas where explosive gas atmospheres may occur during normal operation.
  • Zone 2: Areas where explosive gas atmospheres are unlikely to occur during normal operation; if they do occur, they are occasional and short-lived.
Flammable dust atmospheres are classified into Zone 20, Zone 21, and Zone 22.
  • Zone 20: Areas where an explosive dust atmosphere in the form of a dust cloud is continuously or frequently present in the air for extended periods.
  • Zone 21: Areas where an explosive dust atmosphere in the form of a dust cloud may occur in the air during normal operation.
  • Zone 22: Areas where an explosive dust atmosphere in the form of a dust cloud is unlikely to occur in the air during normal operation, or if it does occur, it will only be for a short period.

How are explosive substances classified?

Explosive substances are divided into three categories:
  • Category I: Explosive gas mixtures in coal mines, mainly composed of methane (CH₄).
  • Category Ⅱ: Explosive gas mixtures in factory environments, divided into three subgroups: Ⅱ A, Ⅱ B, and Ⅱ C.
  • Category Ⅲ: Explosive dusts and fibers, divided into three subgroups: ⅢA, ⅢB, ⅢC.
ⅢA: Combustible fibers, such as cotton fibers, hemp fibers, and wood fibers.ⅢB: Non-conductive dusts, such as coal dust, flour, and plastic powders.ⅢC: Conductive dusts, such as metal powders like aluminum powder, magnesium powder, and zinc powder (higher ignition risk).
 

Category

Explosive gas temperature group

T1

T2

T3

T4

T5

T6

Ⅰ

Methane

 

 

 

 

 

Ⅱ A

Ethane, propane, acetone, styrene, chlorobenzene, toluene, aniline, carbon monoxide, formaldehyde, aniline

Butane, methanol, ethanol, propylene, vinyl chloride, butyl acetate, amyl acetate

Pentane, hexane, heptane, decane, octane, gasoline, chlorobutane

Diethyl ether, trichloromethane

 

Ethyl nitrite

Ⅱ B

Coke oven gas, cyclopropane, acrylonitrile

Ethylene oxide, 2-propylene oxide, ethylene, 1,3-butadiene

Dimethyl ether, hydrogen sulfide, tetrahydrofuran, acrolein

Tetrafluoroethylene, diethyl ether

 

 

Ⅱ C

Water gas, hydrogen

Acetylene

 

 

Carbon disulfide

Ethyl nitrate
 
Equipment Temperature Group Gas Ignition Temperature Maximum Permissible Surface Temperature
T1 >450°C ≤450°C
T2 >300℃ ≤300℃
T3 >200℃ ≤200℃
T4 >135°C ≤135°C
T5 >100℃ ≤100℃
T6 >85℃ ≤85℃

What are the main explosion proof technologies?

Explosion protection type

Symbol

Principle

Permitted Usage Area

Flameproof

da

The electrical components of the device are sealed within a robust metal casing, which prevents the escape of flames and explosive pressure even if an explosion occurs inside the casing, thus preventing the ignition of flammable or explosive substances outside.

Zone 0

db

Zone 1

dc

Zone 2

Increased safety

eb

By optimizing the device structure and using high-quality materials, the likelihood of ignition sources being generated during normal operation and in fault conditions is reduced.

Zone 1

ec

Zone 2

Intrinsic

safety

 

ia

By limiting the voltage and current of the circuit, the electrical sparks and thermal effects generated by the device during normal operation or fault conditions are always kept below the ignition energy of flammable and explosive substances.

Zone 0 Zone 20

ib

Zone 1 Zone 21

ic

Zone 2

Zone 22

Pressurized

 

pxb

Inert gas (such as nitrogen) or clean air is continuously supplied into the equipment casing, maintaining the internal pressure higher than the external ambient pressure, preventing flammable and explosive gases from entering the casing, thus eliminating contact between ignition sources and the flammable medium.

Zone 1 Zone 21

pyc

Zone 1 Zone 21

pzc

Zone 2 Zone 21

Oil immersion

ob

Live parts that may generate sparks, arcs, or high temperatures are completely immersed in a specific insulating oil (such as transformer oil). The oil's properties of air isolation, heat dissipation, and arc suppression prevent ignition sources from contacting external flammable and explosive substances, thereby achieving explosion-proof protection.

Zone 1

oc

Zone 2

Powder filling

q

Components that generate heat or sparks are embedded in a casing filled with quartz sand. The heat dissipation and arc suppression properties of the quartz sand prevent arcs and sparks from igniting the external medium.

Zone 1

Encapsulation

ma

The electrical components of the device are encapsulated and solidified with insulating materials such as epoxy resin and polyurethane, isolating the electrical components from contact with external flammable and explosive substances, while also limiting the temperature rise of the components.

Zone 0

Zone 20

mb

Zone 1

Zone 21

mc

Zone 2

Zone 22

n

na

During normal operation, there are no sparks or high-temperature risks, and ignition sources are eliminated from the source through structural optimization.

Zone 2

nr

Through a highly sealed enclosure design, the "breathing effect" caused by temperature differences and pressure changes between the inside and outside of the equipment is suppressed.  The rate and total amount of external explosive gases entering the enclosure are strictly controlled, ensuring that the concentration of the infiltrated gas remains below the lower explosive limit; even if the internal equipment generates sparks or high temperatures during normal operation, it will not ignite the mixed gas.

nc

There are no ignition sources during normal operation, and through redundant designs such as overcurrent/overheating protection, the device can withstand single faults (such as short circuits or contact sticking) as specified by the standards, and there will still be no ignition sources even in the event of a fault.

tD

ta

Designed for explosive dust environments, it prevents dust from accumulating on the equipment surface and being ignited through methods such as enclosure protection, limiting surface temperature, and eliminating static electricity.

Zone 20

tb

Zone 21

tc

Zone 22

How to understand explosion proof marks？

 

Ex de IIC T6 GbEx: Explosion proof markde: Explosion proof method, d Flameproof, i Intrinsic safety, m Encapsulation, q Powder filling, e Increased safety, nr Restricted breathingIIC: Hazardous Substance Classification, I Coal Mine, II Ground and Other Locations - Gases, IIC Hydrogen and Acetylene, IIB Ethylene, IIA Non-mineral Methane and PropaneT6: Temperature Group, T1 450°C, T2 300°C, T3 200°C, T4 135°C, T5 100°C, T6 85°CGb: Equipment Protection Class, G Gas, a Very High, b High, c Low

 

Ex tb ⅢC T80°C DbEx: Explosion proof marktb: Explosion proof method, i Intrinsic safety, m Encapsulation, t Dust ignition protection by enclosure, ta(EPL”Da”), tb(EPL”Db”), tc(EPL”Dc”)ⅢC: Hazardous Substance Classification, Ground and Other Locations - Dust, ⅢA Fibers and Flocculents, ⅢB Non-Conductive Dust, ⅢC Conductive DustT80°C: Maximum Surface TemperatureDb: Equipment Protection Class, D dust, a Very high, b High, c Low

How to choose Explosion Proof devices?

 

Before selecting explosion proof electrical equipment, First of all, we must understand the hazardous medium and the area where the equipment will be used. Then, determine the explosion-proof type, category, level, and temperature group of the equipment in sequence.(1) Select the explosion proof type based on the area:Zone 0: Ex da, Ex ia, Ex maZone 1: db, px, py, q, ob, eb, ib, mbZone 2: dc, pz, oc, ec, ic, mc, nA, nR, nc(2) Select the category and level of the equipment based on the category and level of the hazardous gas:If the medium is ⅡA: Select ⅡA~ⅡC equipment;If the medium is ⅡB: Select ⅡB~ⅡC equipment;If the medium is ⅡC: Select ⅡC equipment;(3) Determine the temperature group of the equipment based on the temperature group of the hazardous gas.
Hazardous Location Gas Group Ignition Temperature Optional Equipment Group
T1 >450°C T1~ T6
T2 >300℃ T2~ T6
T3 >200℃ T3~ T6
T4 >135°C T4~ T6
T5 >100℃ T5~ T6
T6 >85℃ T6

 

(1) Select the category and level of equipment based on the category and level of the hazardous dust.If the medium is ⅢA: Select ⅢA~ⅢC equipment;If the medium is ⅢB: Select ⅢB~ⅢC equipment;If the medium is ⅢC: Select ⅢC equipment;

Conclusion

Explosion proof is not only a technical requirement, but also a fundamental guarantee for industrial safety. Only through a systematic understanding of explosion proof zone division, hazardous media classification, explosion proof types, and equipment selection principles can we effectively reduce explosion risks in complex hazardous environments, ensuring personnel safety and stable production operation. If you have needs for explosion proof PA and intercom projects, please contact us; we can provide IP PA and intercom explosion proof terminals.
FAQS
Q1: Is IP67 explosion proof?
In IP 67, the number 6 indicates the level of protection against solid objects, and the number 7 indicates the level of protection against liquids. Meeting the IP67 protection level does not mean that the equipment is explosion proof.
Q2: What does ATEX stand for?
ATEX means that the product can be used safely in hazardous environments where flammable substances could cause an explosion, preventing them from becoming an ignition source.
Q3: Are Ex and ATEX the same?
Both Ex and ATEX are for equipment used in explosive hazardous locations, but ATEX is applicable to the European market, while Ex can be used as a general standard, but equipment exported to the EU still needs to meet ATEX requirements separately.
Q4: Where are explosion proof equipment typically used?
Oil & gas refineries, chemical plants, paint booths, mining, and wastewater treatment facilities.
Q5: What are the 3 elements of an explosion?
Ignition source, explosive substance, and oxygen.
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