What CompEx is, who runs it, where it is recognised, and where Ex01-04 sits in the scheme.

CompEx is short for Competency in Explosive Atmospheres. It is a scheme that proves an individual has the core competence to work on electrical and instrumentation equipment in hazardous areas without introducing danger into the workplace. It is not a product approval and it is not a paper qualification. It is proof that you, the person, can do the work safely.

It was created by EEMUA (the Engineering Equipment and Materials Users Association) and is run today by CompEx Certification Limited (CCL), part of the JTL Group. It is built on the IEC 60079 series of international standards, primarily parts 10, 14 and 17. Those three run through everything you will sit: classifying the area, installing to standard, and inspecting and maintaining it.

Why it exists

Hazardous-area work went unregulated until a long line of disasters forced standards into being (Chapter 03 covers those). The law now says a person must be competent before they work where danger could arise, and CompEx is the recognised way of proving that competence. It is the practical answer to the legal duty set out in the Electricity at Work Regulations, which we come to in Chapter 04.

The CompEx module map

The full scheme is around fifteen modules, each covering a different type of work or environment, plus refresher versions to requalify. This guide is Ex01-04, the Gas and Vapours modules, because it is the most widely sat and the foundation most hazardous-area careers are built on. Here is how the whole scheme fits together.

Refresher modules (Ex01R-04R and Ex07R-08R) exist to requalify before your certificate expires, rather than sitting the full course again.

Where it is recognised

CompEx is built on the IEC 60079 international standards, so it carries weight anywhere that works to the IEC zone system: the UK, Europe, the Middle East, Africa and much of Asia. That is why it is a benchmark on oil and gas, petrochemical, LNG and offshore work.

Some countries do not use CompEx and run their own scheme instead.

First time or refresher

If this is your first CompEx, you sit the full five-day course and all the assessments (Chapter 02 breaks the week down). Pass, and your certificate is valid for five years.

Before those five years are up, you take a shorter refresher to requalify rather than starting from scratch. This is why the scheme has a built-in cycle, and why the skills stay current rather than fading after one exam.

What you walk away with

A CompEx Certificate of Core Competence, valid five years, earned by passing four practical assessments and one closed-book online exam. The full breakdown is next, in Chapter 02.

What the week looks like, the five things you are assessed on, and how to handle each one.

How the week works

CompEx Ex01-04 is a five-day course. The early part of the week is instruction and hands-on practice on the rigs. The back end is assessment. You are tested on five things: two practical installations, two inspections and one online exam. You must pass all five to be certified.

The four practical assessments

The installs test your ability to work to documentation and to wire, terminate and install hazardous area equipment competently. The inspections test the same discipline in reverse: working to the documentation, spotting the faults and hazards, exactly as you would on a live site. The exact timetable varies by training centre, but the assessments and their lengths do not.

The online exam

The fifth test is a closed-book online multiple-choice exam: 60 questions in 90 minutes. Watch the scoring: right-clicking an answer scores it out, so read every question twice and answer with a left click. We drill the real question style in Chapter 10.

What the exam covers

The 60 questions are drawn from across the whole syllabus. There is no published split of marks per area, but everything falls into five knowledge areas, and they are exactly the chapters of this guide.

What you must pass, and resits

You must pass all four practical assessments and the online exam to receive your certificate. Slip up and the rules are clear.

How to handle the week

Nerves are normal. The candidates who do well are the ones who slow down and work methodically. On the practicals, take your time on selection and follow the drawings exactly. On the inspections, work to a system so you do not miss faults. On the exam, read every question twice and be deliberate with every click. Preparation is what removes the panic, and that is what this guide is for.

Where this all came from, what it takes to cause an explosion, and the disasters that wrote the rules you work to.

What a hazardous area is

A hazardous area is any place where flammable gases, vapours or dusts can be present in enough quantity to cause an explosion. Equipment installed there has to be specially designed and tested so it cannot set off that atmosphere, whether from an arcing contact or a hot surface.

Think of an ordinary light switch. The small spark when you flick it is harmless in your house. Put that same spark in a flammable vapour and it can start an explosion. That is the whole problem this qualification exists to manage.

You will find hazardous areas on oil refineries, offshore platforms, drilling rigs, gas storage and transmission, sewage works, paint stores, distilleries, pharmaceutical plants, grain mills, sugar refineries, fertiliser stores and saw mills.

What it takes to explode

A gas or vapour explosion needs three things present at once: fuel, oxygen and a source of ignition. Take any one away and there is no explosion. This is the fire triangle, and it is the idea every other rule is built on.

Fuel is the hazardous gas, vapour or mist. Oxygen comes from the air around us (roughly 21%). The ignition source is the one we have most control over, and it is where most of the engineering effort goes.

Where it all began

The first hazardous areas were found in coal mines, which carried a double hazard: firedamp (the gases in a mine, mainly methane) and coal dust. Standards were born here, because the lamps and candles miners carried kept causing fires and explosions.

Early gas detection was crude. The Davy lamp came first, around 1815: a fine wire mesh that lets gas pass in but stops a flame passing back out, so any small ignition inside the lamp could not reach the mine. Then the canary bird was introduced in the 1890s, and used right up until 1986, reacting to gas before the miners did.

The disasters that wrote the rules

Almost every rule in this guide was paid for by an incident. Three you should know:

The law and the standards behind the work, kept to only what the exam asks of you.

Primary and secondary law

Primary legislation is an Act of Parliament, part of statute law, for example the Health and Safety at Work Act 1974. Secondary legislation is the regulations made under an Act (Statutory Instruments), which let the law be updated without writing a whole new Act, for example DSEAR 2002.

HASAWA 1974

The Health and Safety at Work Act is the primary piece of legislation covering occupational health and safety in the UK. It places a general duty on employers to ensure, so far as is reasonably practicable, the health, safety and welfare of their employees, and that duty extends to other people too, not just staff. It also places duties on manufacturers of equipment, covering its design, construction and safe operation.

Electricity at Work Regulations 1989

The EAWR covers electrical systems, work activities and protective equipment, including protecting equipment from harsh conditions: mechanical damage, excessive temperature or pressure, wet, dirty, dusty or corrosive conditions, and flammable or explosive substances.

The ATEX Directives

ATEX is the name for the two European Directives that control explosive atmospheres. Know which is which, and the UK regulations each one became.

Memory hook: 114 is for the equipment, 153 is for the workers. Remember

EPS Regulations and DSEAR

The EPS Regulations (Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres) put ATEX 114 into UK law. Equipment must meet the Essential Health and Safety Requirements before it is sold or put into service, normally proven by testing and certification through a third-party Notified Body. Equipment for Zone 2 only can be self-certified by the manufacturer.

DSEAR (Dangerous Substances and Explosive Atmospheres Regulations 2002) puts ATEX 153 into UK law. It requires employers to assess the risks of fire and explosion from dangerous substances, then eliminate or reduce them as far as is reasonably practicable, and to classify and mark hazardous places.

Certification marks

The certification marks you will see on a nameplate.

IECEx / ATEX

IECEx is the international scheme, accepted worldwide. ATEX is the European scheme, shown by the Ex-in-a-hexagon mark. Kit is very often certified to both, so you will see both marks on the one nameplate.

UKCA

UKCA (UK Conformity Assessed) is the Great Britain mark brought in after the UK left the EU. Kit sold in Great Britain now carries UKCA, usually alongside CE, and the Ex requirements are identical under both.

Standards and the 60079 series

A standard is an agreed way of doing something, written by experts and approved by a recognised body. Three levels matter: BS (British, from BSI), EN (European, from CENELEC) and IEC (International). Electrical equipment for hazardous areas runs in the 60079 series.

The three you will lean on most are 10 (classify), 14 (install) and 17 (inspect), the same three from Chapter 01.

The properties that decide whether a gas will ignite, and the numbers the exam keeps coming back to. Get these straight and equipment selection in the next chapter falls into place.

Flash point

The flash point is the lowest liquid temperature at which a liquid gives off enough vapour to form an ignitable vapour and air mixture. Below it, there simply is not enough vapour to catch.

Vapour density: does the gas rise or fall?

Air is the reference, given a relative density of 1.0. A gas lighter than air rises. Heavier than air, it sinks and gathers at the lowest point.

Why it matters on site: heavier-than-air vapour pools in pits, trenches and bunds, exactly where you do not want an ignition source.

The flammable range

A gas only ignites within a window of concentration. Too little fuel and it is too lean. Too much and it is too rich. Between the two limits, it will go.

Remember  LFL is the Lower Flammable Limit (too lean below it). UFL is the Upper Flammable Limit (too rich above it). The band between them is the flammable range.

There are more numbers in this chapter than anywhere else in the guide, and that puts a lot of people off. You do not need them all at once. Take one property at a time, learn what it tells you, and the figures start to stick on their own.

Minimum ignition energy

Minimum ignition energy (MIE) is the smallest amount of energy needed to set off a gas and air mixture. The lower that number, the more easily the gas ignites, and it is one of the things used to sort gases into groups.

µJ = microjoules. The less energy a gas needs, the more dangerous it is, which is exactly why hydrogen sits in the toughest group.

Gas groups

Gases are sorted into groups by how easily they ignite. The more volatile the gas, the less energy it needs, and the tougher the equipment has to be.

Those subgroups sit inside the bigger picture of three equipment groups:

CompEx Ex01-04 is all Group II, gas and vapour. Mining is Group I, dust is Group III.

Ignition temperature

The ignition temperature is the temperature at which a gas ignites on its own, with no spark or flame, just from touching a hot surface. It used to be called the auto-ignition temperature (AIT). This is the number a piece of equipment's surface must never reach.

Temperature classification

The T-class is the maximum surface temperature the equipment can reach. It must always stay below the ignition temperature of the gas around it.

Read an area, choose the right kit, and decode a label without breaking a sweat. This is the chapter that turns the science into selection.

How an area is classified

Hazardous areas are split into zones based on how often an explosive atmosphere is present and how long it lasts. The more likely and the longer-lasting, the more onerous the zone. For gas and vapour the classification standard is 60079-10-1.

Don't try to memorise the numbers yet. Understand the one idea, how often the atmosphere is there, and the zones make sense on their own.

Grades of release

Before the zone comes the grade of release, which is how often a flammable substance escapes. The grade generally decides the zone.

The three zones

Zone drawing symbols

On an area classification drawing each zone has its own hatching. Hover or tap a zone in the table above (or a symbol below) and its pair lights up. Always check the drawing key, but these are the standard symbols.

A worked example: a storage tank

This is the classic one, and it shows how the zones nest. The most dangerous atmosphere is sealed inside the tank, and the risk fades the further out you go.

The vapour space above the liquid is Zone 0 (gas almost always there). Around the vent and seals is Zone 1 (gas likely now and then). A wider envelope is Zone 2 (only if something goes wrong). Past that, non-hazardous.

In plain terms: where you find each zone

Picture a whisky distillery. Deep inside the stills and storage vats is Zone 0, alcohol vapour is almost always there. Around the still vents and sample points is Zone 1. The wider still-house floor is Zone 2. Here is the same idea across a few everyday places.

The link that ties it all together

This is the most important table in the chapter. It connects the zone to the equipment you are allowed to put in it, through the EPL (the IEC marking) and the ATEX category (the European marking). They are two names for the same thing.

The complete picture: every group

The map above is the gas one you live in. For completeness, the same EPL, category and zone link runs across all three environments. Your exam is the middle block, Group II, gas.

Memory hook: the EPL letter (a/b/c) and the category number (1/2/3) always line up, and both point straight to the zone.

IP ratings

The IP (Ingress Protection) code, from IEC 60529, is two digits after the letters IP. The first digit is protection against solids and dust (0 to 6), the second is protection against water (0 to 9). Where a digit is not rated it is shown as an X, for example IPX4.

Reading a label

Put it all together and a marking like Ex eb IIC T6 Gb reads piece by piece. Each part of the string is doing a job:

Alongside it the ATEX marking II 2 G means Group II (surface industry), Category 2, Gas. The same information, the European way.

The certificate number on the label reads the same way. Take Baseefa 19 ATEX 1234 X:

X and U never appear together: X means read the special conditions, U means it is a building block, not standalone equipment.

Four markings you will meet

Read each one at a glance, the way you would on a real piece of kit.

II surface industry · 2 G Category 2, gas (Zone 1) · Ex db flameproof · IIC hydrogen group · T4 surface stays ≤135°C · Gb suits Zone 1.

II surface industry · 2 G Category 2 (Zone 1) · Ex eb increased safety · IIC hydrogen group · T6 surface ≤85°C, the coolest · Gb Zone 1.

II surface industry · 1 G Category 1, gas (Zone 0) · Ex ia intrinsic safety, the only Zone 0 kit · IIB ethylene group · T5 surface ≤100°C · Ga Zone 0.

II surface industry · 3 G Category 3, gas (Zone 2) · Ex nA non-sparking · IIA propane group · T3 surface ≤200°C · Gc Zone 2.

The same kit, around the world

The protection concepts are global, but the marking changes by region. Here is the same flameproof, gas-group IIC, T4 fitting under the three big schemes.

Gas-group cross-reference: IEC IIC covers North American Groups A and B, IIB is about Group C, and IIA is about Group D.

That is the end of the knowledge half of the guide. The General Principles test below covers everything from Chapters 01 to 06.

The heart of the qualification. Each concept is just a different way of breaking the fire triangle, by containing the bang, keeping the gas out, stopping the spark, or starving it of energy.

How protection works

Every concept comes down to one of five basic methods of stopping an uncontrolled ignition:

The concepts at a glance

Tap any concept to jump straight to it.

We take them one at a time below. Each ends with a drill on that exact concept.

This is the biggest chapter in the guide, so do not try to take it in all at once. Work through one concept at a time, use the drill at the end of each to check it has stuck, and come back to the harder ones. Few people hold all of it after a single read, and you are not meant to.

Glands and cable entry

Gland selection comes up on nearly every concept and on the practicals, so learn it once here. A gland seals the cable into the enclosure, holds the ingress protection, and where needed keeps earth continuity. Since 2008 a gland entering a certified enclosure must itself be certified.

Two markings you will see: E1W is for steel wire armoured (SWA) cable, A2 is for non-armoured. A barrier gland (compound filled) is needed on an ignition-capable Ex d enclosure into IIC or IIB+H2, or where the cable length and internal volume demand it. On a gland certificate, X means fixed equipment only and U means it is a component.

Tap any image to expand. Tap the cross-section to see every part of the gland named.

1 2 3 4 5

1. 1Entry componentScrews into the enclosure
2. 2Inner seal (gas seal)Seals on the cable inner sheath
3. 3Armour clamp (olive) + coneGrips and earths the armour
4. 4Outer seal (weather seal)Seals on the cable outer sheath
5. 5Back nutTightens the gland down

The minimum arrangement depends on the enclosure and the entry:

So, do you need an IP washer to hold the minimum IP54? It comes down to the entry:

Ex d Flameproof

Flameproof does not stop the explosion happening. It lets it happen inside a strong enclosure, then contains it and cools the escaping gases through engineered gaps (the flamepaths) so they cannot ignite the atmosphere outside. Containment, not prevention.

The enclosure is solid and robust, built to withstand around 10 bar (150 psi) from an internal blast. Typical materials are cast iron, aluminium alloys, gun metal and stainless steel. Plastics are only allowed where the free internal volume is no more than 10 cm³.

The flamepaths are the joints, flanged, spigot or threaded, where gases escape and cool. The gap is critical: too wide and a flame gets out. Each gas group is defined by its MESG (maximum experimental safe gap), and from that the standard sets the maximum constructional gap allowed for the joint, checked with a feeler gauge, with all cover bolts tool tight. For a small hydrogen (IIC) enclosure that constructional gap is about 0.10 mm, the tightest of all. Solid objects must be kept clear of flamepaths by a minimum distance, which also depends on the gas group.

Cable glands must be Ex d certified with a minimum thread engagement of 5 full threads (6 mm). A barrier gland is needed for direct entry into IIC or IIB+H2 enclosures, or where the cable type and internal volume demand it. Unused holes take certified stopping plugs fitted with special tools.

So which gland do you fit? Work it down from the gas group, the cable length and the enclosure volume:

To keep ingress protection and stop rust, non-setting, non-combustible grease may be applied to the flamepaths, but not on IIC enclosures. Any adaptor used with a gland must itself be Ex d certified, and an imperial opening is sealed with a certified stopper of matching thread.

Ex e Increased Safety

Increased safety takes a normal-looking piece of kit and adds extra measures so that arcs, sparks and excessive temperatures cannot happen in normal service. It prevents the ignition source rather than containing it like Ex d.

The key features: a mechanically strong, impact-tested enclosure, a minimum of IP54, a limited number of terminals, and set creepage and clearance distances with at least 6 mm between live terminals. Since 2008 the glands must be certified (Ex e, de or denR); before that an uncertified gland was fine if it was IP rated and impact tested.

At terminations, no more than 1 mm of bare conductor should show, only one conductor per terminal side unless the certificate says otherwise, and two different-sized conductors need a single compression ferrule to share a terminal.

Ex e enclosures use the gland arrangements covered above. Every cable entry must keep the minimum IP54, and from 2008 unused entries are closed with certified stopper plugs. An Ex d motor fitted with an Ex e terminal box takes an Ex e gland on its SWA cable.

Markings: Ex eb suits Zone 1, Ex ec suits Zone 2.

Ex n Reduced Risk

Reduced risk means that in normal operation, and certain specified abnormal conditions, the equipment cannot ignite the atmosphere around it. It has no fault tolerance, so it is Zone 2 only (EPL Gc). It is an older concept, gradually absorbed into other types and no longer in the current 60079 series, but it still turns up on installed kit. Minimum IP54 where there are bare live parts.

Ex nR is restricted breathing: sealed so an incendive mixture cannot get in. A gland fitting an Ex n enclosure must be certified to at least IEC 60079-0 (the modern triple-certified d, e and t glands are common). Ex nL can be used in an EPL Gc intrinsically safe circuit if its electrical parameters match.

A plain "Ex N" marking is the old standard and is not certified to current CENELEC or IEC standards.

Ex i Intrinsic Safety

Intrinsic safety works by limiting the electrical energy in the hazardous area to below what it takes to ignite the atmosphere. It is the only concept that allows live working without a gas-free certificate, and the only one that can go into Zone 0.

Intrinsic safety is certified as a complete loop, not as single pieces of kit: the barrier, the cable and the field device are assessed together, documented in a Descriptive System Document, and every part has to be justified. The energy is limited by a barrier in the safe area. A zener (shunt diode) barrier needs a dedicated high-integrity IS earth of under 1 ohm, minimum 4 mm². A galvanic isolator does not need a dedicated earth, which is why it is more common today. The barrier (the associated apparatus) holds both IS and non-IS circuits, with a maximum Um of 250V at the non-IS terminals.

Both barriers limit the energy reaching the hazardous area. The Z-System is a zener (shunt-diode) barrier, the K-System a galvanic isolator. Tap any panel to expand.

A zener barrier uses three diodes so it stays safe with two faults (level ia). The marking [Ex ia] in brackets means associated apparatus, the safe-area equipment that feeds the IS circuit. Simple apparatus, a diode, thermocouple, switch or resistor, needs no certification. Enclosures for IS circuits are a minimum of IP2X; an uncertified metallic junction box must avoid light metal and keep 3 mm clearance to earth and 6 mm between separate circuits, while a plastic box in a Zone 1 area uses an Ex eb enclosure. Unused cores are terminated in unearthed terminals.

Ex p Pressurisation

Pressurisation keeps the hazardous gas out by holding a protective gas inside the enclosure at a slight overpressure. Used on control rooms, analyser cabinets and large machines. The safe gas (air, or an inert gas such as nitrogen) is drawn from the safe area, and the enclosure is purged before it is energised. If it exhausts into a hazardous area, a spark arrester is fitted. If an inert gas is used, warning beacons and signs are required. The pressure relief valve is set to no more than 75% of the maximum overpressure.

The current standard adds the EPL as a suffix: Ex pxb and Ex pyb for a Zone 1 (Gb) area, Ex pzc for Zone 2 (Gc). If the kit inside is not ignition-capable and already suits the zone, no pressurisation is needed.

Ex o, q, m, s and op (the rest)

The remaining concepts each keep the gas and the spark apart in their own way:

Combined methods

Kit often uses more than one concept, and the letters then appear in alphabetical order. A flameproof motor with an increased safety terminal box is marked Ex de. The classic exam trap: Ex de is a flameproof (d) body with an increased safety (e) terminal box, not the other way round.

That completes the protection concepts. Installation (Chapter 08) and Inspection (Chapter 09) come next.

Doing it right. 60079-14 is the standard for design, selection and installation, and its whole aim is to stop the installation itself ever becoming the ignition source.

Cables and terminations

Cables for fixed non-IS equipment must be thermoplastic, thermosetting or elastomeric sheathed, or mineral insulated metal sheathed (MICC). Runs through a hazardous area should be continuous where possible. Aluminium conductors, if used, must be at least 16 mm². Fine and multi-stranded conductors must be protected against the strands separating, using lugs or core-end ferrules, never by soldering alone.

When taking non-IS equipment out of service, at least one end of each unused core must be connected to earth.

Cable entry and glands

Choosing a gland comes down to the cable type and the enclosure. An E1W gland is for steel wire armour (SWA). An ignition-capable flameproof enclosure may need a barrier gland, depending on the gas group, cable length and internal volume. On a gland certificate, a "U" means a component and an "X" means specific conditions of use, for example fixed equipment only. As a rough guide, around 20 mm of inner insulation should be visible inside the gland.

Earthing and bonding

Earthing gives fault current a fast path to clear the protective device, and bonds all metalwork to the same potential so nothing can arc across. A loose or high-resistance earth is itself an ignition source.

Ex enclosures have an internal earth terminal and an external earth tag for supplementary bonding. Because the enclosure is painted or anodised, a serrated (star) washer goes under the tag to bite through the coating to bare metal, otherwise the joint is high-resistance and will not clear a fault. On armoured cable, the armour is earthed by the gland cone (the olive), so a slack or wrongly assembled gland is a recordable fault.

If light metals not listed in 60079-0 are used in construction, an ignition hazard assessment is needed to prove it is safe.

On the day: the Ex01 and Ex03 installs

Here is what the two install assessments actually involve, so nothing on the day is a surprise. Centres vary slightly, but the shape is the same and the assessors take you through the hands-on work. If you are not from an electrical background, do not let it worry you.

What you are assessed on. Method, not finish. You are marked on following your documentation, using the correct glands, and installing them properly and safely. Before any work: permit, isolate, prove dead, and confirm the area is gas-free. Neatness and cable-tying are not scored, so keep the standard up but do not lose time chasing a tidy job.

Safe isolation and the permit to work

Before you touch anything, on any unit, you make it safe. It is assessed on every practical, and it is the same sequence you would follow on a live site. Your assessor will run you through this.

1. Permit to work. You do not start until the job is authorised in writing.
2. Isolate and lock off. Break every live conductor, the neutral included, at a double-pole isolator. Lock it off, ideally with two locks, yours and the assessor's, and hang a warning label.
3. Prove dead, prove-test-prove. Prove your approved tester on a known live source, test the circuit is dead, then prove the tester again. Only then is it dead.
4. Gas-free certificate. Before any live testing or hot work, the area is tested and certified clear of a flammable atmosphere.
5. Work, then de-isolate and cancel. When you are done, locks and labels off, and close out the permit.

Intrinsic safety cable

The blue one. This is intrinsically safe (IS) cable, and it is what you install and inspect on the IS units, Ex03 and Ex04. The blue sheath is deliberate, it flags the cable as IS so it is never mistaken for power and is always kept segregated. It comes in three forms, tap through them.

Unarmoured SWA Braided

Unarmoured. Insulated and sheathed, with no armour. Protection comes from what it is run in, conduit or trunking, rather than built into the cable.

Barrier glands

Throughout the week you will be introduced to barrier glands. The two types you will most likely be assessed on are compound, better known as putty, and the MDS.

Compound, the putty. A two-part epoxy compound you knead together and pack around the cores by hand, filling every void to form the seal. The traditional way, and still common.

1 / 5The barrier gland, explodedtap to step through

MDS, the multi diaphragm seal. The newer system: a moulded seal with a sealed port for every core, so each core feeds through its own diaphragm instead of packing putty. Quicker, cleaner, and the way the kit is heading. Tap through it.

Equipment only stays certified if it is maintained. 60079-17 sets out how to inspect it, at what grade, and how often.

The three grades: how you inspect

The three types: when you inspect

Portable and personal equipment: checked visually by the user before each use, a close inspection at least every 12 months, and a detailed inspection every 6 months for enclosures opened often, such as battery housings.

Recording faults

Faults are recorded against codes: A general, B installation, C environment. The schedules split into tables: Table 1 for Ex d, e and n, Table 2 for Ex i, Table 3 for Ex p and Table 4 for Ex o.

On site, every certified item is logged in the Ex Register, the master list of what is installed, its certificates and its inspection history, so an auditor can see the whole picture. Responsibility runs in a chain: the manufacturer certifies the equipment, the installer fits it correctly, and the site operator keeps it maintained.

How the inspections work

The inspections are where most marks are won and lost, and they reward a calm, methodical approach. Treat it exactly like a real site inspection, because that is what it is.

Example documentation

On all four of your assessments you are handed documentation, including diagrams like the examples below, that you work and inspect against in your booth. You may be checking your equipment is the correct type, in the correct zone, and free of faults, or making sure you are wiring correctly on the practical assessments. Take your time, and always follow your documentation.

EX02 · Ex d, e, n

EXAMPLE

EX04 · Ex i

EXAMPLE

You are in your own booth, with a rig that has faults built into it. Here is exactly how it runs:

1. Isolate the booth first. Before you touch anything, make it safe. Every single time.
2. Work in three passes, in this order: Visual, then Close, then Detailed.
   • Visual what you can see, no tools
   • Close opening covers and using access gear, nothing taken apart
   • Detailed opening it up with tools and test gear, de-energised
3. Log each fault as you find it. Write its code (the check it fails) and the grade you found it at, straight onto the sheet, exactly like the example below.
4. One line at a time. Work every item on the schedule in order. Methodical beats fast, and you miss nothing.

Faults that come up

Every bay is rigged differently, so the exact faults change, but they are drawn from the same list. These are the ones that show up again and again, learn to spot them and nothing on the day is a surprise. And never try to copy the person next to you, every booth is rigged differently.

EX02 Inspection (standard Ex d, e, n) · potential faults you may face on the day

EX04 Inspection (intrinsically safe, Ex i) · potential faults you may face on the day

Across the week you sit five assessments: two install practicals, two inspections, and a closed-book online exam. Centres vary how they run the week, but you are always taught the material before you are assessed on it. You have drilled the theory chapter by chapter, so here is how each one runs and how you walk in ready.

Assessment week: how it runs

The week mixes instruction and assessment, and centres vary how they deliver it. You are taught the material for each unit, then assessed on it, so you never sit something you have not been shown. Four of the assessments are hands-on, in your own bay: two installs, Ex01 and Ex03, where you wire and terminate equipment to a drawing, and two inspections, Ex02 and Ex04, where you are handed a rig with faults built in and have to find and record them. Ex01 and Ex02 cover Ex d, e, n and p equipment; Ex03 and Ex04 cover intrinsically safe (Ex i) equipment. The week usually finishes with the online exam: 60 questions, 90 minutes, closed book, and every unit within it must be passed on its own. You are marked on getting it right and, above all, doing it safely.

The full mock exam

Sixty questions split across the four units, Ex01 to Ex04, on a strict ninety-minute clock, exactly like the real paper. Every sit pulls a fresh paper from the full bank, so it is never the same twice. When you finish you get your overall score and a unit-by-unit breakdown against the 80% target, so you know exactly which unit to go back and tighten.

Resits and the rules

EX01 · EX02 · EX03 · EX04

Each unit stands alone. You will only resit the unit you fail, not the whole exam week.

Multiple choice test

Four sections in one paper, Ex01 to Ex04. Pass every section, or resit the whole paper, not just the one you failed.

Resit

You get two further resit attempts, within twelve months of your original assessment. Fail those and you sit the whole course again.

Already drilled into the guide

Ten topic tests sit through the guide, each one where its material lives. The protection concepts alone carry six. The mock above is the full dress rehearsal.