Electrical Equipment in Hazardous Areas

A hazardous area is defined as a place where concentrations of flammable gases, vapours, or dusts occur.

IRDI System’s products, including the protocol converter with safety barrier and nozzle receiver, are designed and certified to operate in hazardous areas, where hydrogen gas is present under normal conditions. See Table 1.1 for a list of flammable gases categorized into groups.


Representative Gases

IAll Underground Coal Mining. Firedamp (methane)
IIAIndustrial methane, propane, petrol and the majority of industrial
IIBEthylene, coke oven gas and other industrial gases
IICHydrogen, acetylene, carbon disulphide

Table 1.1 Flammable Gas Groups

Temperature classification of electrical equipment dictates that any part of the equipment that may be exposed to hazardous atmosphere cannot exceed 80% of the auto-ignition temperature of the gas or vapour in the area. These temperature groups are shown in Table 1.2.

GroupTemperature C°

Table 1.2 Temperature Classification Groups

Certification in the European Union

In the EU, hazardous locations are categorized by zones. For example, a Zone 1 area is defined by the presence of vapour of gas for long periods of time under normal operating conditions. This translates to 10-1000hours per year or 0.1-10% of the time. Refer to Table 2.1 for a description of the zones.


Presence of potentially explosive gas, vapour, or mist

Safe areaAn area where there is low risk of explosion. For example, the presence of aerosols or paint cleaner in an office is more of a fire risk than an explosion risk.
Zone 2Potentially explosive gas, vapour or mist is only present under abnormal conditions, or under 10hours/year or 0.01% of the time.
Zone 1Potentially explosive gas, vapour or mist is present for long periods of time under normal operating conditions. Generally this is defined as 10-1000hours/year or 0.1-10% of the time.
Zone 0Potentially explosive gas, vapour or mist is present all the time. Generally, this is defined as 1000hours/year or >10% of the time.

Table 2.1 Zones Defined By Presence of Explosive Gases

In the EU, there are different protection techniques according to the hazardous zones. For example, if the electronic equipment operates in Zone 0, Ex ia protection is required. See Table 2.2 below for the classification of protection techniques.

Ex Zone
Ex dFlameproof (explosion proof) enclosure – all electrical circuits are enclosed in a house strong enough to contain any explosion or fire that may take place inside.1, 2
Ex iaIntrinsically safe – the electrical energy available in circuits and equipment is limited to a level too low to ignite mixtures in a hazardous area.0, 1, 2
Ex ibIntrinsically safe – the electrical energy available in circuits and equipment is limited to a level too low to ignite mixtures in a hazardous area.1, 2

Table 2.2 Classification of Protection Techniques According to Hazardous Zones

The Equipment Protection Level (EPL) is specified for several types of protection. This is linked to the equipment’s use in the zone it operates in and the hazardous material present. Table 2.3 shows the classifications that are relevant to gases.

GroupEx riskZoneEPLMinimum type of protection
II (gas)Explosive atmosphere > 1000h/year0Gaia, ma
II (gas)Explosive atmosphere between 10 – 1000h/year1Gbib, mb, px, py, , e, o, q, s
II (gas)Explosive atmosphere between 1 – 10h/year2Gcn, ic, pz

Table 2.3 Equipment Protection Level for Zones With Hazardous Gases

Certification in North America

In North America, hazardous locations are categorized by Classes and Divisions, or Zones (similar to EU zones). Refer to Table 3.1 & Table 3.2 for a description of these Classes and Divisions. When zones are used in North America, classification is categorized according to EU zone definitions.

ClassHazardous material in surrounding atmosphere
Class IHazardous because flammable gasses or vapours are present in the air in quantities sufficient to produce explosive or ignitable mixtures
Class IIHazardous because combustible or conductive dusts are present
Class IIIHazardous because ignitable fibres or flying’s are present, but not likely to be in suspension in sufficient quantities to produce ignitable mixtures.

Table 3.1 Classes of Hazardous Atmospheres

DivisionPresence of Hazardous Material
Division 1The substance referred to by class is present during normal conditions
Division 2The substance referred to by class is present only in abnormal conditions

Table 3.2 Divisions of Hazardous Atmospheres

IRDI Product Certification

IRDI nozzle receiver and protocol converter are certified for the European Union (ATEX) and North America (NEC), Japan (TIIS) and Korea (KTL). Below are the certifications of each of our products.
    • Nozzle receiver:
      • ATEX – Ex ib IIC T4
      • NEC – Class I Zone I AEx ib IIC T4 Gb
      • NEC-Class 1 Div 2 IIC T4
      • TIIS- ib IIC T4
      • KTL-Ex ib IIC T4
    • Protocol converter:
      • ATEX – [Ex ib] IIC Gb
      • NEC – Class I Zone I [AEx ib] IIC Gb
      • TIIS (ib) IIC
      • KTL-[EX ib] IIC
    • Test signal generator/IR Transmitter-Class 1 Div 2:
    • Heavy Duty Vehicle products-No intrinsic safety certfication
Let’s use the ATEX-certified IRDI protocol converter to demonstrate the meaning of the certification terms. The ATEX protocol converter is certified to operate in Zone 1, where gas group “IIC” (hydrogen, acetylene, or carbon disulphide) is present for long periods of time under normal operating conditions. The protocol converter requires an equipment protection level of “Gb”, which in turns requires the nozzle receiver to be intrinsically safe (protection technique “Ex ib”). Note that the ATEX-certified IRDI nozzle receiver has a temperature group classification. The IRDI nozzle receiver is certified as temperature group T4, which means the nozzle receiver will not reach temperatures beyond 135C° during operation. Its ambient operation temperature is from -40 to 80 C°.
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