ATEX hazardous area classification.

Certification and compliance requirements for ATEX categories

Each ATEX product category must meet specific requirements before being placed on the European market. The certification procedure depends on the level of risk and the possibility that the product will be exposed to potentially explosive atmospheres. Below is an overview of the main categories and related procedures:

M1 and M2 (mining environments)

Equipment intended for use in mines, categories M1 and M2, generally requires the involvement of a Notified Body (NB) for product certification and, for category M1, also for company certification. A declaration of conformity accompanied by instructions for use is also mandatory.

1G and 1D (high-risk areas, gas or dust)

Products intended for areas with a high risk of gas (1G) or dust (1D) require certification of the equipment and, in some cases, of the company's production system by an NB. In this case too, a declaration of conformity and instructions for use are always mandatory.

2G and 2D (medium risk areas, gas or dust)

For these categories, product certification by NB is usually required, while the company may proceed with self-certification in certain circumstances. However, the declaration of conformity and the accompanying technical documentation remain mandatory.

3G and 3D (low risk areas, gas or dust)

Under these conditions, the manufacturer may use self-certification, ensuring that the product complies with the required standards. However, the declaration of conformity and instructions for use must still be provided.

These distinctions ensure that each piece of equipment is checked and documented in proportion to the risks present in the operating environment.

Explosibility limits: LFL and UFL

When it comes to explosion risk, two fundamental parameters come into play: the lower flammable limit (LFL) and the upper flammable limit (UFL). In simple terms, these limits define the concentration range of a combustible substance in the air within which an explosion can occur.

LFL (Lower Flammable Limit): represents the minimum concentration of gas, vapour or dust required, in the presence of an ignition source, to generate an explosive reaction. Below this value, the mixture is too “lean” (not enough fuel) to explode.

UFL (Upper Flammable Limit): indicates the maximum concentration above which the mixture becomes too “rich” to explode, as there is too much fuel and too little oxygen.

In short, an explosion can only occur when the concentration of the substance is between the LFL and UFL and there is an ignition source, such as a spark. It is important to remember that these limits vary depending on the substance, pressure and oxygen content in the environment: for example, methane, sugar dust and petrol have different values.

At this point, we can see how CE-marked equipment and apparatus are classified.

CE-marked equipment and apparatus

The ATEX 2014 Directive classifies products into categories according to their level of protection and the degree of danger of the environment in which they will be used. Below are the ATEX classifications.

Group 1

This directive includes products used in underground or open-cast mines, as the test methods for danger and protective measures are similar for both materials. It is divided into two categories, depending on the level of protection required:

M1: Products that remain functional in the presence of an explosive atmosphere. “Very high” level of protection.

M2: Products that are switched off in the event of an explosive atmosphere forming.

High level of protection.

Group 2

Products used in surface industries. It is divided into three categories, depending on the level of protection required (area of use). In the case of use in environments with gas, the category is identified with the letter G, in the case of dust with the letter D

1G or 1D: continuous or long-term presence of explosive atmosphere. Protection level ‘very high’

2G or 2D: occasional presence of explosive atmosphere. Protection level ‘high’

3G or 3D: absence or short-term presence of explosive atmosphere. Protection level ‘normal’

99/92/EC on the safety and health of workers in explosive atmospheres

According to ATEX Directive 99/92/EC, potentially explosive atmospheres are divided into zones