What “Ex” Really Means: Understanding ATEX Equipment in Confined Spaces

In the confined-space industry, many instructors teach that EX means a piece of equipment is intrinsically safe; Really!

The term “Ex” is used so frequently in the classroom and on PowerPoint slides that it is often taken for granted. Ex lighting, Ex gas detectors, Ex radios, Ex ventilation fans, and Ex tools appear routinely on permits, equipment lists, rescue plans, and method statements, to the point that the marking can fade into the background of everyday operations, lose its importance, and become the rule of opinion that it means intrinsic safety.

Despite this widespread use, there remains a persistent misunderstanding of what “Ex” means, what it does not mean, and why it is fundamental to confined space safety.

This misunderstanding is not just academic; it has real and sometimes severe consequences.

Ex is not a marketing label, a quality badge, or a guarantee that something cannot explode. It is a specific technical and legal designation confirming that equipment has been designed and assessed so that it will not become an effective ignition source when used in a potentially explosive atmosphere, within clearly defined limits.

The types of EX protection available are:

"d" : flameproof enclosure.
"e" : increased safety.
"i" : intrinsic safety. EX i
"m" : encapsulation.
"n" : type of protection ‘n’ .
"o" : oil immersion.
"p" : pressurization.
"q" : powder filling.
"t" : protection by enclosure.

Understanding the types of protection is a core competence requirement for anyone working in, supervising, or equipping confined space operations (Confined Spaces Regulations 1997; L101 paras 23-24).

So, what is it for? An explosive atmosphere exists when a flammable gas, vapour, mist, or combustible dust is mixed with air in such proportions that ignition can result in fire or explosion.

In confined spaces, this condition is prevalent because gases can accumulate rapidly, ventilation may be restricted or fail, and the space's enclosed nature can amplify the consequences of ignition, particularly if you have been taught that everything with the EX marking is intrinsically safe by default.

Typical confined space hazards include methane released from sewage or sludge, hydrogen sulphide from biological decay, petrol or solvent vapours from residues or cleaning agents, and process gases released from pipelines, valves, or plant failures.

Notably, the presence of an explosive atmosphere does not require a gas alarm to sound. An explosive atmosphere may not be a visible cloud or a strong odour detectable by the human nose. It is the foreseeable potential for such a mixture to form that triggers legal duties (risk assessments) under regulation 5 of the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR Reg 5; L138 paras 121–126).

The concept of Ex equipment sits within the ATEX framework. ATEX is not a single regulation but a framework covering two linked obligations. The two core obligations under ATEX arise from two distinct EU directives and apply to different dutyholders.

ATEX 114 (2014/34/EU) applies to manufacturers, requiring that equipment and protective systems intended for use in potentially explosive atmospheres be designed, assessed, and certified as safe, as evidenced by CE marking and the Ex symbol.

In contrast, ATEX 153 (1999/92/EC) applies to employers and dutyholders, requiring them to assess explosion risks, classify hazardous areas (zoning), and implement appropriate organisational and technical measures to protect workers.

The first obligation (ATEX 114 (2014/34/EU)) concerns equipment placed on the market for use in potentially explosive atmospheres. Manufacturers must design, test, and certify such equipment to ensure it does not ignite an explosive atmosphere under defined conditions, and must clearly mark it so users can determine where it is safe to use.

The second (ATEX 153 (1999/92/EC)) concerns workplaces and requires employers to identify explosion risks, classify hazardous areas into zones, control ignition sources, and protect workers. In the UK, this duty is delivered through DSEAR and supported by ACOP L138, particularly the sections on hazardous area classification and workplace risk control (DSEAR Regs 5–7; L138 paras 51–53).

In Great Britain, this requirement is enforced through the Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations 2016 (EPS Regulations).

When a piece of equipment is marked “Ex”, it means that its design addresses all credible ignition mechanisms. This includes controlling electrical sparks, limiting hot surface temperatures, preventing static discharge, managing friction and mechanical impact, and accounting for foreseeable internal faults.

What Ex does not mean is that the equipment is indestructible, universally safe, or immune to misuse. Ex equipment is only safe within the limits defined by its marking and only if it is used, inspected, and maintained in accordance with those limits (DSEAR Reg 6 and Schedule 1(4)(5)(a)(b)(c)(d); L138 paras 241(b)et al.

ATEX coding is critical. The ATEX marking is a compact technical statement that specifies the conditions under which the equipment may be used. A typical marking such as

“II 2 G – Ex ib IIB T4 Gb” defines equipment group, category, atmosphere type, protection concept, gas group, temperature class, and equipment protection level.

Let's break this down.

II – Equipment Group II.
For use in surface industries such as utilities, water, wastewater, and manufacturing, not for mining.

Equipment Category 2.
Suitable for Zone 1 areas, where a flammable gas atmosphere may occur during everyday work. Designed to remain safe even if one fault occurs.
G – Gas atmosphere.
Intended for use in flammable gas, vapour, or mist atmospheres (not dust).

Ex – Explosion protected.
Confirms the equipment has been designed and certified to prevent ignition in explosive atmospheres.

ib – Intrinsic safety, level “ib”.
The electrical energy is limited, so it cannot cause ignition, even with one fault. Suitable for Zone 1 (not Zone 0). Zone 0 will be identified as ‘’ia’’.

IIB – Gas group.
Suitable for IIB gases (e.g. ethylene). IIB is not ideal for the more easily ignited IIC gases such as hydrogen or acetylene.
T4 – Temperature class.
The maximum surface temperature of 135 °C must be below the target gas's ignition temperature.
Gb – Equipment Protection Level
Provides a high level of protection and confirms suitability for Zone 1 gas atmospheres.

Category to zone alignment is non-negotiable; if a permit identifies a Zone 1 environment, category 3 equipment is therefore not acceptable (DSEAR Reg 7(2); Schedule 3(1), EPS 2016, L138 paras 375–377).

Click Here: DSEAR Markings Wall Chart.

The markings also identify whether equipment is suitable for gas or dust atmospheres and how ignition is prevented. Intrinsic safety is particularly relevant to confined-space work because it limits electrical and thermal energy to levels that cannot cause ignition, even under fault conditions. Gas grouping and temperature class must always match the substances present to prevent ignition (DSEAR Reg 6).

When considering control measures, ventilation alone does not remove the need for Ex controls. Explosive atmospheres can still exist locally or transiently even where ventilation is provided (L138 para 123(g)). Battery-powered equipment is not inherently safe; unless the entire device is Ex-certified, it must be treated as a potential ignition source (L138 para 241(c)).

Ex also does not mean safe indefinitely. Damage, unauthorised modification, degraded seals, or unreadable markings undermine protection. If suitability cannot be confirmed, the equipment must be treated as unsuitable (L138 paras 368–372). This may be a consideration when the gas monitor label is obscured by hire company codes, or worn off completely.

Ultimately, ATEX markings exist for users. In confined spaces, understanding Ex is not optional. If equipment suitability cannot be justified, it must not be taken into the space. Ex compliance is a live control measure that prevents ignition and protects life (Confined Spaces Regulations 1997; L101 paras 91- 93).

Useful References.