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Substitution assessment for hazardous substances in Germany: TRGS 600 procedure, column model and documentation

Before you specify extraction and protective gloves, one question comes first: could a less hazardous substance or process do the job? How the substitution assessment under TRGS 600 works, how to compare alternatives and what belongs in the documentation.

Last updated on 8 min readAMS Go editorial team

Key points at a glance

  • The possibility of substitution is a mandatory part of every risk assessment for hazardous substances in Germany (Section 6 (1) sentence 2 No. 4 GefStoffV); based on the result, substitution must be carried out as a priority (Section 7 (3) GefStoffV).
  • The result of the substitution assessment belongs in the documentation of the risk assessment; if protective measures under Section 9 or 10 are needed, a decision not to carry out a technically possible substitution must be justified (Section 6 (8) sentence 2 Nos. 2 and 3 GefStoffV).
  • TRGS 600 describes the procedure: identify alternatives, pre-select promising ones, compare hazards and technical suitability, and decide after weighing up operational factors – higher costs alone do not rule out substitution.
  • In the TRGS 600 column model, the current substance and the alternative are rated per column – such as acute and chronic health hazards, fire and explosion, release behaviour – on five levels from “very high” to “negligible”; if the alternative is two or more levels better, there must be important reasons for not using it.

What is a substitution assessment?

The substitution assessment (Substitutionsprüfung) is the employer's duty to check, as part of the risk assessment (Gefährdungsbeurteilung), whether a hazardous substance or process can be replaced by a substance, mixture, article or process that is less hazardous overall for employees (Section 6 (1) sentence 2 No. 4 and Section 7 (3) of the Hazardous Substances Ordinance, GefStoffV). If it can, substitution must be carried out as a priority – before technical, organisational and personal protective measures.

The Technical Rule TRGS 600 “Substitution” specifies the procedure. It distinguishes three approaches:

  • avoiding work with hazardous substances altogether, for example through a different manufacturing process
  • replacing hazardous substances with substances or mixtures that pose no or a lower hazard under the conditions of use – for example water-based instead of solvent-based cleaners
  • replacing hazardous processes with less hazardous ones – for example brushing instead of spraying, or granules instead of dusty powder

What the Hazardous Substances Ordinance requires

  • Assess the possibilities of substitution in the risk assessment

    SourceSection 6 (1) sentence 2 No. 4 GefStoffV

  • Substitute as a priority based on the result

    SourceSection 7 (3) GefStoffV

  • Document the result of the substitution assessment

    SourceSection 6 (8) sentence 2 No. 2 GefStoffV

  • Justify not carrying out a technically possible substitution if protective measures under Section 9 or 10 are needed

    SourceSection 6 (8) sentence 2 No. 3 GefStoffV

  • Use carcinogenic, germ cell mutagenic and reprotoxic substances of category 1A or 1B in a closed system if substitution is not technically possible

    SourceSection 10 (1) GefStoffV

  • Report the result of the substitution assessment for these substances to the authority on request

    SourceSection 18 (3) GefStoffV

Substitution assessment in five steps

  1. 1

    Describe the starting point

    Record which hazardous substance or process is used for what: classification, quantity, duration, exposure routes and function in the process – auxiliary substance, component of the product or raw material.

  2. 2

    Identify alternatives

    Evaluate the TRGS on substitutes and substance-specific TRGS, industry solutions and DGUV publications, the safety data sheet (section 7.3), databases such as GESTIS, WINGIS or GisChem, and the experience of other companies. When purchasing, ask the supplier specifically about less hazardous solutions.

  3. 3

    Pre-select promising solutions

    If you find many options, filter them using the key criteria of TRGS 600: health hazards, physico-chemical hazards and release potential.

  4. 4

    Compare hazards and suitability

    Compare the current situation and the alternatives in terms of health, fire, explosion and environmental hazards, for example with the column model, and check technical suitability: function, product quality and consequences for downstream processes.

  5. 5

    Decide, implement, document

    Weigh up operational factors such as costs, effort and protective measures saved, decide and record the result and the reasons. After the changeover, update the risk assessment, operating instructions (Betriebsanweisung), instruction and the hazardous substances register.

Hazardous substances management in AMS GoUpload safety data sheets for substances in use and potential substitutes, have AI extract classification and H statements with source references, and add substances to the hazardous substances register only after approval by a competent person.

Pre-selecting alternatives: what matters

TRGS 600 names three key criteria for pre-selection, which must always be considered together: health hazards, physico-chemical hazards such as fire and explosion, and release potential. Release into the air generally decreases with:

  • liquid instead of gas, paste instead of liquid
  • non-dusty instead of dusty solids
  • a high boiling point (low vapour pressure) instead of a low boiling point
  • water-based instead of solvent-based systems
  • aerosol-free instead of aerosol-forming processes
  • closed instead of open processes and room temperature instead of high temperatures

Comparing alternatives with the column model

The column model (Spaltenmodell) in Annex 2 of TRGS 600 allows a quick comparison using a few details from the safety data sheet. The current substance and the alternative are rated separately in columns for acute and chronic health hazards, environmental hazards, physico-chemical hazards, release behaviour and process – each on the levels very high, high, medium, low or negligible. Some examples:

  • Very high

    Acute health hazardsacutely toxic cat. 1 or 2 (H300, H310, H330)

    Fire and explosionflammable liquids cat. 1 (H224)

    Release (liquids)vapour pressure above 250 hPa

  • High

    Acute health hazardsacutely toxic cat. 3 (H301, H311, H331), skin or respiratory sensitising (H317, H334)

    Fire and explosionflammable liquids cat. 2 (H225)

    Release (liquids)vapour pressure 50 to 250 hPa

  • Medium

    Acute health hazardsacutely toxic cat. 4 (H302, H312, H332), serious eye damage (H318)

    Fire and explosionflammable liquids cat. 3 (H226)

    Release (liquids)vapour pressure 10 to 50 hPa

  • Low

    Acute health hazardsskin irritant (H315), eye irritant (H319)

    Fire and explosionflash point above 60 to 100 °C, no H statement

    Release (liquids)vapour pressure 2 to 10 hPa

  • Negligible

    Acute health hazardsharmless based on experience, e.g. water

    Fire and explosionnon-combustible or flash point above 100 °C

    Release (liquids)vapour pressure below 2 hPa

  • Comparisons are made only within a column, never between columns.
  • The model assumes that the manufacturer has assessed the substances on the basis of available data (safety data sheet sections 9 and 11).
  • If the alternative is two or more levels better in a column, there must be important reasons for not using it.
  • If the alternative is better in some columns and worse in others, the conditions in the company decide – if ignition sources cannot be ruled out, for example, fire and explosion hazards carry more weight.

Older versions of TRGS 600 also contained the effect factor model (Wirkfaktorenmodell), which assigned numerical values to substances based on their hazard characteristics and compared the ratio of these values. The current TRGS 600 names only the column model as an assessment aid. Whatever the model: substitutes must have been investigated at least as thoroughly as the substance they replace; if test data are missing, certain hazardous properties must be assumed (TRGS 600 No. 5.3).

Decision, justification and repetition

If an alternative is technically suitable and reduces the hazard, it should generally be implemented – especially for carcinogenic, germ cell mutagenic and reprotoxic substances of categories 1A and 1B and for acutely toxic substances of category 1 (TRGS 600 No. 5.4). Solutions from the TRGS on substitutes and industry rules are generally considered suitable; anyone who deviates from them must justify this in writing. Higher costs alone are not a reason for exclusion: for weighing things up, Annex 3 of TRGS 600 provides a list of operational factors – from material and disposal costs to protective measures and occupational health care – which you rate qualitatively as ++, +, 0, – or – –.

For documentation, TRGS 600 suggests standard sentences, which you can add to the hazardous substances register as an extra column, for example:

  • “Possibilities of substitution are …”
  • “No possibilities of substitution.”
  • “Solution is already the substitution solution.”
  • “Substitution solution technically unsuitable / does not reduce the hazard sufficiently / operationally unsuitable, because …”
  • “Substitution solution initiated, reassessment by …”

Example: cleaning parts in the workshop

Annex 1 of TRGS 600 works through the assessment for a workshop with ten employees that degreases components with a highly volatile cleaner from spray cans – around five cans per shift. Two alternatives are compared:

  • Characteristics

    Current: highly volatile cleaner (spray can)hydrocarbons, flash point below 23 °C, propellant propane/butane

    Alternative 1: low-volatility cleaner (pump spray bottle)hydrocarbons, flash point above 60 °C

    Alternative 2: cleaning unit with water-based cleanerno volatile hazardous substances

  • Health

    Current: highly volatile cleaner (spray can)inhaling vapours and aerosols, skin contact with degreasing solvents

    Alternative 1: low-volatility cleaner (pump spray bottle)fewer vapours, but stronger degreasing of the skin

    Alternative 2: cleaning unit with water-based cleanerlittle skin contact

  • Fire and explosion

    Current: highly volatile cleaner (spray can)explosive atmosphere from solvent vapours and propellant

    Alternative 1: low-volatility cleaner (pump spray bottle)lower than currently, fire risk from soaked cleaning rags

    Alternative 2: cleaning unit with water-based cleanernone

  • Technical suitability

    Current: highly volatile cleaner (spray can)suitable, observe explosion protection

    Alternative 1: low-volatility cleaner (pump spray bottle)suitable, longer drying time, drip tray needed

    Alternative 2: cleaning unit with water-based cleanersuitable, longer drying time, drip tray needed

Both alternatives reduce the hazard; the water-based cleaning unit eliminates the fire and explosion hazard completely but involves investment and energy costs. This is exactly the trade-off you record with the rating under Annex 3.

Checklist: substitution assessment

  • All activities with hazardous substances checked for substitution options, exceptions for low hazard justified
  • Function of the substance in the process described
  • TRGS on substitutes, industry solutions, databases and suppliers consulted
  • Alternative processes and low-emission forms of use included
  • Health, fire, explosion and environmental hazards of current substance and alternatives compared
  • Data quality of the alternatives checked (safety data sheet sections 9 and 11)
  • Technical suitability and operational factors assessed
  • Decision documented with standard sentence and justification
  • Risk assessment, operating instructions and hazardous substances register updated after the changeover
  • Date for the reassessment set

Free templates for this guide

As PDF and Excel, free – to use in your own company.

Frequently asked questions

Is the substitution assessment mandatory?

Yes. Checking the possibilities of substitution is part of every risk assessment for hazardous substances (Section 6 (1) sentence 2 No. 4 GefStoffV), and the result must be documented (Section 6 (8)). Only if the assessment has found a low hazard can it be dispensed with under TRGS 600.

Do I have to document anything if there is no substitute?

Yes. The result “No possibilities of substitution” also belongs in the documentation. For activities subject to protective measures under Section 10 GefStoffV – i.e. with carcinogenic, germ cell mutagenic or reprotoxic substances of category 1A or 1B – you also briefly name the sources you researched (TRGS 600 No. 6).

How often must the substitution assessment be repeated?

The Hazardous Substances Ordinance does not set a fixed interval. The substitution assessment is part of the risk assessment and is reviewed regularly with it and updated after significant changes or new information (Section 6 (10) GefStoffV). Set a date for the reassessment – TRGS 600 provides the standard sentence “reassessment by …” for this.

Can I decide against substitution for cost reasons?

Only after a traceable weighing-up. Under TRGS 600, higher costs of a substitution solution can be accepted; if the operational factors are essentially affected positively, it must be used. The higher the hazard from the current substance, the more its reduction counts. If you decide against it for business reasons, document the considerations in a verifiable way, for example with the table from Annex 3.

Terms from the glossary

This guide gives a general overview of German occupational safety law and does not replace legal advice. The regulations in force and the rules of the statutory accident insurance institutions are authoritative.

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