Hazardous Area Zones | Zone 1 & Zone 2 | An Explanation Guide to Explosive Atmospheres

Experts In Equipment for Explosive Atmospheres & Hazardous Area Locations

LEADERS IN ATEX INNOVATION | Lock | Door | Heater | Fan

Thorne & Derrick 

Guide to Hazardous Area Zones & Products

Thorne & Derrick International are Specialist Distributors of Hazardous Area Electrical, HVAC & Process Instrumentation Equipment to UK and international projects.

Leaders in the development and distribution of ATEX & IECEx Product Innovations that deliver significant improvements to clients plant, people and operational safety in the explosive atmosphere industries.

Your proactive problem solvers experienced in succession planning for the replacement of obsolete, non-conformant and legacy equipment in hazardous areas.

Your first-choice provider of innovative solutons and competitive products  for the hazardous area industries.

Control Panels | Plugs | Isolators | Enclosures & Junction Boxes | Lighting | Control Stations | Motor Starters | Heat Trace | Gas Detection | Flame DetectionProcess InstrumentationProcess Heating | Ventilation Fans | Security Access Control 

Hazardous Area Electrical Equipment

Competitive Prices | Extensive Stocks | Technical Support | Express Delivery

Hazardous Areas

Gas Groups

Products manufactured for safe installation in explosive atmospheres and hazardous area zones (other than mines susceptible to firedamp) and categorised according to ATEX as follows:

Zone 0 Group II Category 1G – the presence of explosive atmospheres is continuous, frequent or for long time periods

Zone 1 Group II Category 2G – the presence of explosive atmospheres is intermittent in normal operation (likely)

Zone 2 Group II Category 3G — the presence of explosive atmospheres is occasional or for short periods (never in normal operation)

Hazardous Area Zones

Hazardous Area Zones

EXHEAT Heaters & International Hazardous Area Classifications include IECEx, ATEX, INMETRO, GOST & EAC

Hazardous Area Electrical, HVAC & Process Instrumentation Equipment | IECEx, ATEX, INMETRO, GOST & EAC.


Hazardous area lighting for safe use in potentially explosive atmospheres, including Zones 1 / 2 (gases) and Zones 21 / 22 (dusts) certified to ATEX and IECEx.

  • Fluorescent or LED – Emergency, Bulkhead, Well Glass & Floodlights
  • Portable – Handlamps, Torches, Headtorches & Floodlights
  • Temporary Floodlights, Tanklights, Airlamps & Mobile Lighting
Wolf Floodlights Handlamps Tank Lighting - Hazardous Area Zone 1 Zone 2 ATEX

Stockists & Suppliers of Wolf Safety Lamp | Portable Hazardous Area Lighting

Wolf Torches Headlamps Handlamps - Hazardous Area Zone 1 Zone 2 ATEX

Petrel Lighting Floodlights Fluorescent Wellglass - Hazardous Area Zone 1 Zone 2 ATEX

Key Suppliers: Wolf & Petrel | Hazardous Area Lighting | ATEX & IECEx

Control Panels & Distribution Boards

Control panels and distribution boards with Ex d (flameproof), Ex e (intrinsic safety) and Ex de hazardous area certification for Zones 1, 2, 21 & 22 with ATEX and IECEx approvals – stainless steel, aluminium and cast iron customised control panels provide reliable and robust explosion proof electrical distribution and control for LV-HV power, control and instrumentation cables.

Including circuit breakers, load break switches, busbar systems, MCB’s, RCCB’s and inspection windows to client specifications.

Hazardous area explosion protected control and distribution panels:

  • Electrical Distribution Panels
  • Lighting & Heat Tracing Panels
  • Machine Control Switchboards
  • Battery Boxes & Containers
Abtech Pepperl Fuchs Control Panels Distribution Boards - Hazardous Area Zone 1 Zone 2 ATEX

Key Suppliers: Abtech & Pepperl & Fuchs | Hazardous Area Panels | ATEX & IECEx

Control Stations & Push Buttons

Hazardous area control stations, surface or panel mounted, specified for potentially explosive atmospheres and suitable for Zone 1 gas and Zone 21 dust environments (including Zone 2 & 22) – manufactured from stainless steel, plastic or GRP with various push buttons, emergency stops, switches, mushroom heads and indicator lamps integrated into control station. Bespoke solutions, express delivery.

  • Ex ed IIC T4
  • Ex e II T4 

Control station options:

  • Emergency Stop Station
  • Emergency Power Off
  • Emergency Stop Start Station
  • Stop Station & Start Station (Stop/Start)
Abtech Craig Derricott Control Stations Push Buttons - Hazardous Area Zone 1 Zone 2 ATEX

Key Suppliers: Abtech & Craig & Derricott | Hazardous Area Control Stations | ATEX & IECEx

Signalling (Sounders & Beacons)

High-specification explosion protected audible and visual signalling devices (beacons/strobes and sounders/horns) for fire and gas detection in industrial onshore, marine and offshore hazardous locations – with integral flameproof Ex d enclosure (ATEX & IECEx approved). Intrinsically safe, explosion proof and flameproof alarm horn sounders, loudspeakers, beacons, strobes and call points.

ATEX, IECEx, UL, cULs, FM, Ex EAC, ANZEx and INMETRO certified signalling equipment.

  • Sounders
  • Beacons
  • Manual Alarm Call Points
Key Suppliers: R Stahl (Clifford & Snell)

Key Suppliers: R Stahl (Clifford & Snell) | Hazardous Area Sounders & Beacons | ATEX & IECEx


Zone 1 and Zone 2 isolators (switch disconnectors) are ATEX certified to Ex d or Ex e for hazardous area installation – housed in heavy duty cast iron or cast aluminium enclosures with 16A-250A current ratings, 3-4 pole including fire resistant isolators for safety critical electrical circuits.

Hazardous Area Certification: Ex d II 2 GD IIB T4, T5 or T6

Craig & Derricott Isolators - Hazardous Area Zone 1 Zone 2 ATEX

Key Supplier: Craig & Derricott | Hazardous Area Isolators | ATEX & IECEx

Enclosures & Junction Boxes

Zone 1 (21) and Zone 2 (22) hazardous area enclosures for instrumentation, small power or lighting applications – stainless steel, mild steel, glass reinforced polyester, aluminium and polycarbonate certified according to ATEX and IECEx. Also high voltage junction boxes for jointing, terminating and connecting 3.3kV, 6.6kV, 11kV and 33kV power cables in Zone 2 hazardous area.

  • Flameproof Ex d Electrical Enclosures & Junction Boxes
  • Increased Safety Ex e Electrical Enclosures & Junction Boxes
  • High Voltage ATEX Certified Enclosures, 3.3kV-33kV
Abtech Electrical Enclosures Junction Boxes - Hazardous Area Zone 1 Zone 2 ATEX

Key Suppliers: Abtech | Hazardous Area Enclosures & Junction Boxes

Plugs & Sockets

Plugs, sockets and decontactors for low voltage power supply include industrial, high current and hazardous areas decontactors with ATEX certification. Plugs are Ex de explosion proof/protected and compliant with ATEX and IECEx standards suitable for Zones 1 & 2 (Gas) and Zones 21 & 22 (Dust).

  • Single Pole Power Connectors – 680A, IK09, IP66, Hazardous Area Classification II2 G D Ex e IIC
  • Zone 1 & 2 Hazardous Area Compact Plugs – 63A, IK09, IP66 Hazardous Area Classification II2 G D Ex de IIC Gb
  • Zone 1 & 2 Hazardous Area Metal Plugs – 200A, IK10, Hazardous Area Classification II2 G D Ex de IIC
Marechal Plugs Sockets - Hazardous Area Zone 1 Zone 2 ATEX

Key Suppliers: Marechal | Hazardous Area Plugs & Sockets | ATEX & IECEx

Electrical Heating

Hazardous area electrical heating provides frost protection and process temperature maintenance of liquids and gases in potentially explosive atmospheres, including Zone 1 and Zone 2 – complete range of heating cables for mechanical services and pipework.

  • Air Heaters & Air Duct Heaters – Ex d Flameproof & Ex e Increased Safety Electrical Heaters (Zone 1 & Zone 2)
  • Immersion Heaters – Ex d Flameproof Rod, Flanged & Removable Core Heaters (Zone 1 & Zone 2)
  • Water Heaters – Point Of Use Ex d Flameproof Calorifiers & Bulk Storage Heaters (Zone 1 & Zone 2)
  • Line Heaters – Hazardous Area Ex d Flameproof Line Heaters Maintain Process Liquid Flow (Zone 1 & Zone 2)
EXHEAT Electrical Heaters - Hazardous Area Zone 1 Zone 2 ATEX

Key Suppliers: EXHEAT | Hazardous Area Electric Heating | ATEX & IECEx

Drum & IBC Heaters

Electrical heating jackets for reducing viscosity and protecting drums and IBC containers against frost in cold weather process, storage and transportation applications.

  • Drum Heaters – Suit Standard 205 Litre (45 Gallon) DrumsEX Explosion Proof Protection
  • IBC Heaters – Suit Standard 1000 Litre Drums
  • Customised Container & Drum Heaters – ATEX & IECEx

Drum & IBC Heaters - Hazardous Area Zone 1 Zone 2 ATEX

Gas Detection

Portable gas detectors and fixed monitors for the safe and reliable detection of flammable and toxic gases in potentially explosive atmospheres – including methane, hydrogen sulphide, ammonia, carbon monoxide and oxygen depletion monitoring to permit safe working in hazardous area locations and confined spaces.

  • Portable & Fixed Gas Detectors – ATEX & IECEx Certified
  • Single Gas & Multi-Gas Detectors – Flammable & Toxic Gas Detection

Crowcon Hazardous Area Gas Detection

Mobile Communications

Hazardous area certified mobile communication technology including mobile phones, tablets and laptops for maintenance and operations in potentially explosive atmospheres.

  • Mobile Phones – Intrinsically Safe Zone 1 / 21 and Class 1 / Div 1 Hazardous Areas – ATEX
  • Tablet – Hazardous Area Zone 2 / Division 2 Android (Based On Samsung GALAXY Tab Active) – ATEX
  • Laptop – Explosion Proof Ex d Zone 2 Hazardous Area Rugged Laptop  – ATEX
Ecom Mobile Phones Tablets Laptops - Hazardous Area Zone 1 Zone 2 ATEX

Key Suppliers: Ecom Instruments

Solenoid valves

Solenoid valves are used to provide accurate flow control of air, gas, water, oil, and steam – explosion proof valves and solenoid operators certified according to ATEX and IECEx for safe use in potentially explosive Zone 1 and Zone 2 hazardous area locations.

Complete range of 2-way, 3-way and 4-way solenoid valves for handling most fluid control applications available with Class I, Division 2 approvals.

ASCO Solenoid Valves - Hazardous Area Zone 1 Zone 2 ATEX

Key Suppliers: ASCO Numatics


Process instrumentation and measurement sensors for hazardous area locations:

  • Pressure
  • Carbon Dioxide
  • Relative Humidity (RH)
  • Temperature
  • Flow & Air Velocity
  • Dew Point
  • Level

Hazardous Area Process Instrumentation

Hazardous Areas

Hazardous Area ZONES

In many industries, working conditions and manufacturing processes can result in the presence of flammable, hazardous gases, vapours and dusts which can be extremely harmful or fatal to personnel and also cause considerable damage to infrastructure.

In addition, modern day automation has increased the need for electrical equipment being used within hazardous areas and these are areas where flammable liquids, vapours and gases can present a fire or explosion hazard.

International regulations such as ATEX and IECEx have put in place a number of Conformity Assessment Schemes in order to provide assurance that the equipment being used within these areas is manufactured and operated to the highest international standards.

Hazardous Area Zones Explained

Hazardous Area Zones Explained

The definition of the hazardous area zones represent the likelihood of hazardous gas, dust or other hazards being present in a working area.

Hazardous area zones where flammable gases may be present are usually defined and marked on Site Area Classification Drawings.

The following hazardous area zone definitions are from IEC 60079-10.

  • IEC 60079-10-1:2015 : Explosive Atmospheres – Part 10-1: Classification of Areas – Explosive Gas Atmospheres


A place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapour or mist is present continuously or for long periods of time.

ZONE 1 hazardous area

A place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapour or mist is likely to occur in normal operation occasionally.

ZONE 2 hazardous area

A place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapour or mist is not likely to occur in normal operation but, if it does occur, persists for a short  period only.


Zone 20 – Zone 20 hazardous areas are those in which an explosive atmosphere in the form of a cloud of combustible dust is in the air for an extended period of time or frequently.

Zone 21 – A zone 21 hazardous area is classified as having a presence of combustible dust in the form of a cloud occur frequently during normal working operations.

Zone 22 – A working place where an explosive atmosphere in the form of a cloud of combustible dust is unlikely to occur and if it does it would not be for a long period of time.

Once assessed as a hazardous area, signs indicating entry into the zone should be erected in compliance with ATEX requirements – many plants and companies erect signs at each entry point into hazardous areas.


  • IECEx: International Electrotechnical Commission System for hazardous area certification relating to equipment to be used in potentially explosive atmospheres.
  • ATEX: European Directive stipulates and certifies equipment intended for hazardous areas explosive atmospheres to be designed and manufactured to minimize the occurrence and limit the severity of accidental explosions.
  • CSA: Expert source for Ex testing and Ex certification of explosion-proof equipment used in hazardous locations and potentially explosive atmospheres across North America.
  • EAC EX: TR CU Certificate of Conformity for the Russian Customs Union for safety of equipment for use in explosive atmospheres is mandatory for any electrical equipment that is to be operated, or installed, in hazardous areas and potentially explosive atmospheres in these countries.
  • INMETRO: Certification body for Brazil to ensure electrical equipment meets requirements for use in hazardous and potentially explosive atmospheres.
Hazardous Area Classifications

Hazardous Area Classifications

Hazardous Areas & DSEAR

The Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) sets out the requirements and guidelines that employers must follow to control the risks from fire, explosions and corrosive substances.

DSEAR definitions for hazardous area zones use the term “dangerous substances” instead of “flammable substances” – this does not align with IEC or CENELEC definitions.

DSEAR guidelines set out the minimum requirements for the protection of workers from fire and explosion risks related to hazardous substances and potentially explosive atmospheres.

The regulations state that employers must put control measures in place to either remove the risks or control them – putting controls in place to reduce the effects of any incidents involving dangerous substances.

DSEAR applies whenever:

  • There is work being carried out by an employer (or self-employed person)
  • A dangerous substance is present at the workplace
  • The dangerous substance could be a risk to the safety of the people as a result of fires, explosions or similar energetic events

DSEAR applies to workplaces where any dangerous substances are present, used or produced and these can be any premises or part of premises used for work. This can include industrial and commercial premises, land based and offshore installations, mines and quarries as well as construction sites and vehicles.

A dangerous substance or mixture of dangerous substances can create a risk to people’s safety from fires or explosions or similar events. Liquids, gases or dusts that may be found in the workplace can all be classed as dangerous substances.

Preventing & Controlling Risks In Hazardous Areas

Employers must put in place, adequate control measures to eliminate risks from dangerous substances or reduce these risks as much as possible and as is reasonably practicable. Where it is not fully possible to totally remove the risk, employers must make sure the correct control measures have been taken to reduce the effects of any harmful event.

The best solution to eliminate the risk entirely is to replace the dangerous substance completely with another substance or alternatively, use a different working process. This is known as substitution in the regulations.

Examples of controlling hazardous area risks and control measures include:

  • Reducing the quantity of dangerous substances
  • Avoiding the release of any dangerous substances
  • Preventing the formation of a hazardous area atmosphere
  • Collecting, containing and removing any hazardous releases into a safe area
  • Avoiding ignition sources and adverse conditions

Hazardous Areas Under Control

Hazardous area classification should be carried out as an integral part of a site risk assessment and should be used to identify any places or working areas in which ignition sources are required and also to identify areas in which such controls are not needed.

Once a hazardous area has been identified or an area designated as potentially hazardous, it should be classified by zone in order to distinguish those areas that have a high chance of an explosion occurring.

The definitions of each hazardous area zone also recognises the chance of a fire or explosion occurring in that area at the same time as an ignition source being present. There are many benefits of companies carrying out full risk assessments of potentially hazardous areas in addition to complying with regulations. These benefits include:

Cost Savings Hazardous area certification reduces the need for additional testing and certification resulting in faster access to new markets.

Improved Safety The assurance that equipment is manufactured and operated according to strict international standards.

Instant Verification Products with ATEX, IECEx and other international standard markings that are instantly recognisable demonstrate that the products conform and are suitable for use in potentially hazardous areas.

Hazardous Area Directives | ATEX & IECEX

ATEX European Hazardous area certifications

ATEX European Hazardous area certifications


Two European Directives, the ATEX Equipment Directive 94/9/EC (ATEX 95) and the ATEX Workplace Directive 1999/92/EC (ATEX 137) address safety in hazardous areas where there is a danger from potentially explosive materials – the ATEX Directives relate equally to places where combustible dusts or flammable gases may be present.

ATEX 95 Directive is intended to remove barriers to trade by ensuring that the quality of equipment, wherever it is manufactured in the EU, meets rigorous essential safety requirements. This ATEX Directive categorises equipment into groups. Group 1 applies to equipment intended for use in underground mines. Group II (2) applied to all other equipment liable to be endangered by explosive gases or vapours. Group III (3) applies to all other hazardous area equipment liable to be endangered by explosive dusts.

ATEX 137 Directive is aimed at ensuring the health and safety of workers whilst in their workplace – ATEX 137 categorises workplaces into zones. Zones provide a measure of the probability of the presence of a dangerous mixture with air on any flammable gas or combustible dust. Zones with flammable gases are zone 0, 1 or 2 and zones with combustible dusts are zone 20, 21 or 22 hazardous areas.

The ATEX directive is one of the most commonly recognised hazardous area certifications and is widely adopted by members of the Euopean Union (EU) in order to facilitate free trade within the EU by aligning technical and legal requirements in the member states  for products to be used within hazardous areas.

The name ATEX is derived from the French ATmosphére EXplosif, meaning explosive atmosphere.

ATEX covers electrical and mechanical equipment as well as protective systems which may be used in potentially explosive atmospheres and became mandatory for Europe in June 2003.


IECEx Hazardous Area Certification

IECEx Hazardous Area Certification

The IECEx directive facilitates the international exchange and acceptance of product-safety test results amongst participating laboratories for national approval or certification in one or more countries without the need for additional testing.

The IECEx certification system is endorsed by the United Nations and is internationally recognised as the certificate system for promoting the safety of equipment, services and personnel that are associated with devices, systems and installations used in explosive atmospheres.

International Classifications

Other international hazardous area classifications for the marking and purchasing of equipment include INMETRO for the Brazilian market, GOST for products in Russia and Ukraine, NEC for North America.

Selection Of Hazardous Area Equipment

When selecting equipment for use it is vital to carry out a thorough working area inspection and ensure the correct working zone has been specified. If a working area is designated as a Zone 2 area when in reality it is either Zone 1 or Zone 0, then this can have potentially disastrous effects.

Equipment to be used in hazardous areas must be certified as intrinsically safe for use in the relevant zone and possess the relevant certification that relates to the country in which it is to be used.

Safety Parameters When Working Within A Hazardous Area

The ignition temperature of flammable gases or flammable liquid refers to the lowest temperature of a heated surface at which the gas or liquid will ignite therefore the highest surface temperature of any equipment must always be less than the temperature of the surrounding area.

Temperature classifications T1 to T6 have been introduced for hazardous area equipment – the equipment is assigned to a temperature class according to its maximum surface temperature. The temperature classes are:

Temperature Class Max Equipment Surface Temperature Ignition Temperature Of Combustible Substances
T1 450°C >450°C
T2 300°C >300°C
T3 200°C >200°C
T4 135°C >135°C
T5 100°C >100°C
T6 85°C >85°C

Working within Hazardous Area Industries

Hazardous working areas can arise in almost any industries however due the nature of production facilities and bi-products, industries such as oil and gas, petrochemical, power generation and some food production locations tend to have more naturally occurring hazardous and potentially explosive locations.

The oil and gas industry is widely considered to be the most hazardous for an international classification perspective with safety and correct product specification being paramount. Any incidents, explosions or endangerment of human life is widely reported and in such a heavily regulated industry, this can lead to large fines and other sanctions being imposed on companies.

In addition to the manufacturing process, hazardous areas can also occur during transportation and the presence of hazardous gases and dusts is extremely common.

There are many examples of well documented explosions occurring within hazardous areas such as the Deepwater Horizon oil spill in which BP was fined $18.7bn – the largest ever fine in U.S environmental history.

Explosion Proof Equipment