In our article What Is Module B? we covered EU-Type Examination in detail; but Module B is only one of the modules used in ATEX's conformity assessment system. In this article we cover all modules from A to H together, comparing which module is used in which situation and which category.
What Is the Conformity Assessment Modules System?
Under the EU's New Legislative Framework, Decision No 768/2008/EC provides for a modular system that defines conformity assessment routes of varying depth depending on the product's risk level. This system is not specific to ATEX alone; it is used across CE legislation generally, but which module is mandatory for which category under ATEX is defined directly in the annex of Directive 2014/34/EU. The modules can be considered in two main groups: "design-stage modules" and "production-stage modules."
Design-Stage Modules
| Module | Name | What Happens? |
|---|---|---|
| Module A | Internal production control (self-declaration) | No notified body; the manufacturer declares based on its own technical file. |
| Module B | EU-Type Examination | A notified body examines the product sample/design file and issues a type-examination certificate. |
Module A can only be used for Category 3 equipment and does not require notified body involvement. Module B is almost always mandatory for Category 1 and 2 equipment, and is not sufficient on its own — it must always be completed with a production-stage module. We explained how Module B works in detail in our article What Is Module B?.
Production-Stage Modules
| Module | Name | What Happens? |
|---|---|---|
| Module C2 | Internal production control + supervised product checks | The manufacturer does its own check; the notified body performs random sample checks at intervals. |
| Module D | Production quality assurance | The notified body audits the manufacturer's quality management system during the production stage. |
| Module E | Product quality assurance | The notified body audits the quality system at the product's final inspection and testing stage. |
| Module F | Product verification | Direct testing/checking is carried out on each product or via statistical sampling. |
| Module G | Unit verification | Each individual product unit is examined one by one, fully; used for special/one-off equipment. |
| Module H | Full quality assurance | The notified body comprehensively audits the entire quality system, from design to production. |
Which Module Combination Is Used for Which Category?
For Category 3 equipment, only Module A is sufficient and is used on its own. For Category 2 equipment, typical combinations are Module B + C2, Module B + D, or Module B + E. For Category 1 equipment and Group I (mining) equipment, which requires a higher level of assurance, one of Module B + D, Module B + F, or Module B + G is used; alternatively, Module H, which covers design and production in a single process, is also chosen by some manufacturers. We covered how category determination is made in our article What Is ATEX?.
Factors to Consider When Choosing a Module
When choosing among the combinations legislation allows, the manufacturer's own production structure and existing quality system are decisive. For a manufacturer that already has an ISO 9001-like quality management system in place, transitioning to Module D or H is relatively easier because the existing system can largely be reused. For companies with low-volume or custom-design production, Module G may be more suitable since it prescribes separate examination for each unit. For manufacturers with mass production who want to prove product consistency through statistical sampling, Module F may be preferred.
How Does Module Choice Affect Cost and Timeline?
Module choice directly affects both the cost and duration of the process. Module A is the lowest-cost and fastest option because it does not involve a notified body. More comprehensive modules like Module H increase both cost and operational burden because they require higher notified body fees and regular surveillance audits. To strike this balance correctly, we covered cost factors in detail in our article What Determines the Cost of ATEX Certification?.
Relevant Directives and Standards
The legal basis of the modular conformity assessment system is Decision No 768/2008/EC, which defines all modules from A to H in general terms. Which module is mandatory for which category under ATEX specifically is stated in the relevant articles of ATEX Equipment Directive 2014/34/EU. The technical standards referenced in applying the modules are the EN IEC 60079 series.
Step-by-Step Process
- Determine your product's equipment group and category.
- List the module combinations legislation allows for your category.
- Choose the combination best suited to your existing quality system and production volume.
- Prepare the required technical file for the design-stage module (Module A or B).
- Structure your quality system or testing/checking process according to the chosen production-stage module.
- Apply if notified body involvement is required.
- Set up the periodic surveillance or checking calendar required by the chosen module.
Most Common Mistakes
- Trying to use a module not permitted for the category (for example, only Module A for a Category 1 product).
- Choosing a design-stage module but never implementing a production-stage module.
- Choosing a module that doesn't match the existing quality system and being forced into unnecessary restructuring.
- Overlooking that unit-based modules like Module F/G are impractical for mass production.
- Choosing a module based only on cost without assessing its fit with the production structure.
Frequently Asked Questions
Is a manufacturer completely free in choosing a module?
No, the modules that can be selected are restricted by legislation according to the equipment's category. Only Module A can be used for Category 3, while for Category 1 one of several module combinations (B+D, B+F, B+G) must be chosen.
What is the difference between Module D and Module H?
Module D covers only the quality assurance system of the production stage, while Module H covers full quality assurance covering both the design and production stages; Module H provides a more comprehensive and higher level of assurance.
When is Module G preferred?
Module G (unit verification) is preferred for equipment that is not mass-produced, is special-purpose, or is produced as a one-off; in this module each individual product unit is examined separately.
Who chooses the module?
Module choice is the manufacturer's responsibility, but the choice is limited to the combinations legislation allows; the manufacturer determines the one most suited to its own production structure and quality system, among the permitted options.
Can more than one module be used for the same product at the same time?
Yes, a design-stage module (for example Module B) and a production-stage module (for example Module D) are used together, one after the other; this combination covering two different stages is standard practice for Category 1-2 equipment.
Can the module choice be changed?
If there is a significant change in the production process or quality system, the manufacturer can switch to another module permitted by legislation; but this transition requires a new conformity assessment process.
When is Module C2 used?
Module C2 includes random product checks in addition to internal production control, and is generally preferred together with Module B for medium-risk Category 2 equipment.
What is the difference between Module E and Module D?
Module D focuses on the quality assurance of the production process, while Module E focuses on the product's own quality assurance system (final product control); both are audited by a notified body but look at different points.
How does module choice affect cost?
More comprehensive modules (for example Module H) increase cost because they require a higher notified body fee and more frequent surveillance audits; Module A is the lowest-cost option since it does not involve a notified body.
What happens if the module choice is made incorrectly?
A module choice that does not match the category leads to the conformity assessment being deemed invalid and the process having to be run again from scratch with the correct module; this results in loss of time and cost.
Conclusion
ATEX's modular conformity assessment system is a flexible but strictly rule-bound structure that provides varying depths of assurance depending on product risk level. Choosing the correct module combination both ensures legal compliance and allows the manufacturer to run a process compatible with its existing quality system and optimized for cost.
Let's determine the right module combination for your product together. For more information, see our ATEX consultancy service or get in touch.
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