latest version: 5.12

Frequently asked questions

Introductory answers to frequently asked questions are offered about technical and general issues. Click on a subject heading below to view questions and answers relating to your selection. Links throughout the answers will guide you to further information on our website or from other sources. Should you have any further questions, please consult our contact page.

About Us

How can MeClas be defined in one sentence?

The MeClas tool allows classifying complex inorganic materials like ores and concentrates, complex intermediates, alloys or UVCBs, recognizing the specific properties and assessment techniques for inorganics, using the most updated information on toxicity references and self classifications available.

Why was MeClas set up?

In the hazard identification and classification of complex inorganic materials, companies, consortia and commodities often faced significant but common difficulties, including the following:

  • Most complex materials in the metals sector contain widely different metals (compounds) and minerals, beyond what is covered by the REACH Consortia, thereby requiring extensive physico-chemical, toxicity and ecotoxicity reference data sets
  • Consortia usually do not have automatic access to such data from other metals/consortia.
  • Any classification and labelling tool requires continuous updating, as more (self-) classifications and toxicity reference values become available with time as a result of test or data gathering obligations under REACH and CLP. A continuous updating is required to avoid inconsistent classifications appearing with time

MeClas was set up in order to address those difficulties, aiming at facilitating the exchange of information, improving efficiency, adequacy and consistency of the generated classifications through collective action. It also provides a common system to ensure the quality and confidentiality of proprietary data.

Where can I find MeClas?

MeClas is available on You will have to register in order to access the MeClas tool and all supporting information. Registered users will be notified on license conditions. A completed license agreement can be sent to

How does MeClas work?

MeClas proposes a tiered and inorganic specific approach, allowing refinement of the classification in accordance with the availability of data. The tiers are shown here below:

MeClas has a core block, which includes Toxicity and Ecotoxicity and Toxicity Reference Values (ERV and TRV), forming its basis with the classification rulings. Those ERV and TRV values are provided by the data owners (e.g. consortia or companies), and a system has been set up in MECLAS to both ensure confidentiality for proprietary information and quality control of the provided values. MECLAS has a two-layer structure:

  • first layer: on the first layer, consortia can identify Reference materials, generate classifications, save and store those in the tool.
  • second layer: the companies and other interested bodies who have access to the Reference Material classifications can derive company-specific material classifications.

What are the basic principles behind MeClas?

MeClas is governed by a number of principles and it is expected that all licence holders of the tool agree to these principles when buying licence rights to the MeClas tool:

  • MeClas follows classification guidance and implements it in accordance with the legal ruling and provided technical guidance (ECHA, UN). For the EU, MeClas will not deviate from the proposed CLP guidance unless ECHA agrees to the proposed deviations approach
  • The MeClas tool will be adapted to the classification ruling when necessary.
  • MeClas classifies and ranks Ecotoxicity Reference Values (ERV) according to quality and following a strict procedure. New higher quality information overrules older or lower quality info after assessment by the quality control committee
  • ERVs and TRVs are never made public unless the consortia provides explicit written agreement to do so
  • All consortia and company-specific (reference) compositions are stored on (a protected part of) the MeClas server enabling any changes to the classification system, ERV or TRV values to be made automatically and on an immediate basis.

How safe is MeClas?

MeClas works with unique passwords. A unique password is provided for reference substances.

Can I check more than 5 complex mixtures with MeClas?

Yes. The limit of 5 materials relates to the number of Reference materials (e.g. matte, speiss, flue dust,…) that can be introduced with the free license, stored at the same time. However, within this group of 5 entries, all users can ‘play and assess classifications’ for as many materials they would like to check. If required, more reference materials can be included when the user becomes a full license holder.

A Reference material/substance is recognized by its speciation and dissolution kinetics (e.g. Transformation dissolution results) (if used). A new reference material entry is required as soon as a complete new speciation profile or new Transformation dissolution evidence needs to be entered.

What are the main differences between MeClas and other classification tools? What is the added value of MeClas?

In order to clarify the differences between the existing available classification tools, a short comparison was made here below between:

  • classification calculation modules in available SDS software packages
  • the “Arche classification Excel tool” distributed by ECI/ICMM/Euromines (limited edition),
  • and MeClas, distributed by Eurometaux and Arche

The following parameters/functionalities were compared:

  • integration of mixture rules (for CLP/DPD or for GHS)
  • consideration of CLP Annex VI (and 1st ATP)
  • possibility to include self-classifications
  • user-friendliness and costs
  • standalone versus on line tool
  • possibility to carry out a tiered approach
  • advanced user management system
  • possibility for companies to build in some flexibility
  • selling the concept/methodology at ECHA level + EU member States
  • existence of a helpdesk
  • generation of SDS, product portfolio management system, labeling + printing functionalities

Use of MeClas

How can Consortia and companies work together on classification?

MeClas allows for a smoothly cooperation between Consortia and Companies by the use of Reference materials, i.e.:

  • The Consortium puts a “Reference material” in MeClas, defined by its elemental concentration, and optionally Speciation, Mineralogy, Transformation Dissolution or Bio-elution data (corresponding to the different MeClas tiers). The consolidated information will determine the hazard category and differentiations depending on the CLP or DSD ruling,
  • Companies that get a “reference material specific password” from a consortium have access to the Reference material descriptions and classifications for those substances the Consortia granted it for, under the condition they have registered to MeClas
  • There is no limit set on the number of “user specific passwords”, meaning that Consortia can provide unlimited numbers of passwords and that companies can obtain different user specific passwords from different consortia

What are the costs related to both licences?

The fees for MeClas are set as follows (all costs are exclusive of VAT, if relevant):

  • Full MeClas license: min. 3000€.
  • MeClas free license. Restricted access members are not members of the MECLAS Steering group

How is MeClas governed?

A Steering Group overviews the progress and advises and decides on priorities for the next year. Every full licence holder of MeClas is considered as a Steering Committee member. A steering meeting, defining guidance and priorities, will be organised twice a year.

  • The Steering Committee members define the need for, priority and timing of the updates according to the budget possibilities.
  • The Steering Committee decides by quality majority (2/3) in favour of a proposal

Do I have to change my SDS or Labels as soon as MeClas reviews a classification?

MeClas provides hazard assessments to the best and most recent knowledge level possible. It is up to the user to decide when and how he uses the outcome of the MECLAS classification for downstream obligations like SDS, labels and others, as a function of the law and national/permit requirements.

Do I need MeClas if my company already has in-house SDS/classification software?

MeClas and existing in-house SDS/classification software should be seen as complementary tools. MeClas has deliberately no SDS generation or labelling functionalities to avoid overlap. Existing in-house SDS/Classification software typically does not have the latest self-classifications/ERV/TRV values nor specific metal related issues such as elemental versus mineralogical/species analysis and TDP and bio-elution calculation modules. Experience has shown that differences between MeClas and other classification software tools are usually caused by more recent self-classifications in MeClas.

Can the “self-classifications” be toggled off, in view of current difficulties with M factors and self-classifications?

Some licence holders would like a distinction to be made between considering or not considering self-classifications. According to DG ENV and ECHA, it is assumed that you know the self-classifications as soon as the inventory becomes public, and must then update without undue delay (3-6 months). The “on and off toggle” is most probably not required on a long-term basis within the EU, but until such time as the inventory becomes public it would have relevance. Moreover, toggling of Annex 1 and only using self-classification is relevant for non-EU countries.

It would be feasible to introduce such a toggling on/off system, but that this would constitute a software investment. It was agreed to assess timing, costs and difficulties

What if the RAC was to decide upon/change a classification for an Annex VI substance?

MECLAS would have to be updated at the moment of publication of the ATP. MECLAS would consequently stick to the formal legal conclusion so as to ensure acceptance/use of the tool.

What should be done with TDP and bio-elution data required for the MeClas Tier 2?

It is up to the data owner to decide who has access to these data. MeClas will not take on ownership of data. However, differences in data availability may generate inconsistent classifications.

Why can't we enter TDP data for metal powders, and only for massives?

You can enter TDP data for metal powders in the same field of the TDP data for the massives. To determine the Tier 2 classification the amount of each metal released is compared to the ERV values of those metals. Since the ERV values for massive and metal powder are equal, the same field can be used to enter the metal powder TDP data.

MeClas populates all of the TDP columns with values of 100 %. Why was this done if in many cases there is no data?

TDP percentages were automatically set to 100 % to avoid an underestimation of the classification result (= worst case assumption). If the field should be left blank then no transformation/dissolution factor is assumed and thus would probably lead to an underestimation of the classification. If the metal TDP was measured then the input value in the TDP column must be manually changed. 

How come the classification is different from the metal classification if we design a metal substance with 100% of one metal?

MeClas is a tool to classify inorganic mixtures and is therefore using the CLP mixture rules to derive the classification. Therefore, when metals are contributing to other endpoints then their own classified endpoints, it is possible this results in a more severe classification.

Is it possible to see the "background database" of classifications?

You can access the database when you export the calculation results in Excel. It was decided, for reasons of full transparency, to include the background database for each calculation export (given that the database is dynamic). To retrieve the database, just calculate the classification of any composition that you have created. Click Excel export/calculations to download the spreadsheet containing a sheet named bgDB.


You must register in order to access the MeClas tool and all supporting information. A short description of the Terms of conditions can be downloaded. The manual gives an idea on the basic functionalities of MeClas.


MECLAS is freely available to use by metal industry and authorities. Reached your maximum number of 5 compositions?

Find out how to upgrade your account by contacting