The suitability of equipment used in hazardous areas is often based on a common but incorrect assumption:
"If the equipment is Ex, there is no problem."
However, field inspections show that a significant portion of the equipment used in many facilities is either incorrectly selected or incompatible with the hazardous area in which it is installed. This situation mainly arises from misinterpretation or complete neglect of the Ex marking on the equipment.
Within the scope of ATEX, the suitability of equipment is not determined solely by being "Ex certified," but must be evaluated together with the environmental conditions, zone classification, gas group, and temperature class. The primary reference for this evaluation is the Ex label on the equipment.
For this reason, the Ex label is not merely a technical detail; it is a critical source of information that determines whether the equipment can be safely used in the field.
In this article, we examine the information contained in Ex equipment labels from a technical perspective and explain how this information should be correctly interpreted in practice.
01The 3 Most Common Critical Mistakes in the Field
Errors in Ex equipment selection are generally not caused by the technical properties of the equipment itself, but by the misinterpretation of these properties.
Recurring critical mistakes observed during field inspections directly compromise explosion safety.
The presence of the Ex marking on equipment does not mean it can be used in all hazardous areas.
Parameters such as:
define where the equipment can be safely used.
For example, using equipment that is not suitable for IIC in a hydrogen environment can create a serious ignition risk. The equipment may be accepted as suitable simply because it is "Ex," while in reality it is operating in the wrong environment.
One of the most common situations encountered in the field is:
The label exists → it is read → but not correctly analyzed
For example:
The temperature class is often overlooked. However, the maximum surface temperature of the equipment must remain below the ignition temperature of the surrounding atmosphere.
A critical and often overlooked issue:
The equipment may be correctly selected, but the installation may be incorrect.
For example:
In such cases, the explosion protection concept of the equipment is compromised.
Field assessments therefore evaluate:
together. Equipment must always be considered as part of a system, not in isolation.
02How to Read an Ex Label Correctly (Step-by-Step Approach)
The suitability of Ex equipment must always be evaluated in relation to the environment in which it is used. Therefore, the first step is to correctly define the environment.
It must be clearly determined whether the environment contains gas or dust, what the zone classification is, and which substances are present.
An incorrect zone classification can cause even technically correct equipment to pose a risk in the field. Therefore, the evaluation process always starts with the environment, not the equipment.
Ex equipment labels follow a standardized structure. This typically begins with the "Ex" marking, followed by parameters such as protection type, gas group, temperature class, and equipment protection level.
Each of these parameters defines the operational limits of the equipment. For proper interpretation, they must be evaluated collectively rather than individually.
The protection type indicates how the equipment is made safe for use in hazardous environments.
In some equipment, explosions are contained within the enclosure, while in others, ignition sources are prevented or energy levels are limited.
This concept affects not only the design of the equipment but also installation and maintenance requirements. Therefore, the protection type must be evaluated together with its field application.
Gas groups classify the explosion risk of the environment, ranging from IIA to IIC, with increasing hazard levels.
Equipment suitable for a higher-risk group can be used in lower-risk environments, but not vice versa.
This distinction becomes especially critical in environments containing highly reactive gases. Incorrect group selection can lead to serious risks, even if all other parameters are correct.
The temperature class defines the maximum surface temperature of the equipment and is one of the most frequently overlooked parameters in the field.
The surface temperature must always remain below the ignition temperature of the surrounding atmosphere.
If this limit is exceeded, the equipment can become an ignition source even without producing sparks. Therefore, the temperature class is not just a label parameter but a critical safety criterion.
The Equipment Protection Level (EPL) defines the zones in which the equipment can be safely used.
This parameter reflects practical safety limits rather than theoretical compliance.
A mismatch between zone classification and EPL will result in direct non-compliance. Therefore, both parameters must always be evaluated together.
03Field Application: ExA Inspection Approach
In field evaluations of Ex equipment, correctly reading the label alone is not sufficient. This evaluation must be supported by a systematic inspection methodology.
Within ExA inspections, the suitability of equipment for its environment is assessed using the following critical questions:
What Do Field Data Show?
IEC 60079-17 inspections conducted within the scope of ExA demonstrate that Ex equipment suitability is often not correctly assessed based solely on label information.
The following issues are frequently observed:
These findings highlight that Ex equipment suitability should not be evaluated with a simple "label present/absent" approach, but through a systematic and data-driven inspection methodology.
04Statistics from Inspections of Over 120,000 Equipment Items
Source: ExA inspection data
* Non-compliance rate for these specific inspection questions only
Conclusion
Holistic Evaluation Approach
An Ex label cannot be evaluated in isolation. Environmental conditions, equipment characteristics, and installation details must all be considered together.
A correct approach requires a systematic evaluation process that integrates all these parameters.
In this way, the Ex label becomes not just a technical marking, but the primary reference for safe operation in the field.