Occupational exposure limits (AGW) and workplace measurement under TRGS 402 in Germany

What is an occupational exposure limit (AGW)?

The occupational exposure limit (Arbeitsplatzgrenzwert, AGW) states the average concentration of a substance in workplace air up to which acute or chronic harm to health is generally not expected (Section 2 (8) of the Hazardous Substances Ordinance, GefStoffV). The values are listed in TRGS 900, which is drawn up by the Committee on Hazardous Substances (AGS) and published by the Federal Ministry of Labour. They apply as a shift average for exposure of usually eight hours a day, five days a week; the employer must ensure they are met (Section 7 (8) GefStoffV).

• Acetone

  AGW in ml/m³ (ppm)500

  AGW in mg/m³1,200

  Excursion factor (category)2 (I)

• Ethanol

  AGW in ml/m³ (ppm)200

  AGW in mg/m³380

  Excursion factor (category)4 (II)

• Toluene (skin absorption)

  AGW in ml/m³ (ppm)50

  AGW in mg/m³190

  Excursion factor (category)2 (II)

• Xylene, all isomers (skin absorption)

  AGW in ml/m³ (ppm)50

  AGW in mg/m³220

  Excursion factor (category)2 (II)

• General dust limit

  AGW in ml/m³ (ppm)–

  AGW in mg/m³1.25 (respirable) / 10 (inhalable)

  Excursion factor (category)2 (II)

The values are taken from TRGS 900; always check the current version before using them. A substance's AGW can also be found in section 8 of the safety data sheet.

Assessment criteria and short-term values

TRGS 402 names three binding assessment criteria: occupational exposure limits under TRGS 900, acceptable and tolerable concentrations for carcinogens under TRGS 910, and assessment criteria from substance-specific TRGS. Where there is no binding value, you can use as an aid:

• Limit value proposals of the MAK Commission of the German Research Foundation (DFG)
• Limit values from other countries, for example from the IFA database “GESTIS – International limit values”
• DNEL values under the REACH Regulation from the safety data sheet
• Company or industry assessment values

Short-term values limit peaks above the shift average, usually over 15 minutes. They are expressed as an excursion factor (Überschreitungsfaktor): category I covers substances with a local effect or respiratory sensitisers (base value 1), category II substances with a systemic effect (base value 2) – up to a maximum factor of 8 in each case. No more than four short-term peak phases are permitted per shift, ideally one hour apart; the shift average must always be met (TRGS 900 no. 2.3). For substances without a short-term value, a factor of 8 applies (TRGS 402 no. 5.2.2).

Assessing inhalation exposure: procedure under TRGS 402

1. 1

   Record activities and define the work area

   Include all work processes and operating states, including servicing and maintenance. Record the relevant conditions on site: quantities, processes, ventilation, extraction, time spent and position relative to the emission source.

2. 2

   Identify hazardous substances

   Identify input materials, reaction products and substances formed during work such as welding fume or engine exhaust – sources are the hazardous substances register and safety data sheets – and compile the assessment criteria.

3. 3

   Choose the assessment method

   Measurement or a non-measurement method – what matters is that it gives a clear picture of exposure over the shift and during peaks.

4. 4

   Evaluate the result

   The substance index (Stoffindex) is the shift average divided by the assessment criterion. If several substances with an AGW occur, the substance indices are added up to the assessment index (Bewertungsindex); substance indices of 0.05 or more must be included.

5. 5

   Reach and document the finding

   The finding (Befund) is “protective measures adequate” or “inadequate”, without taking PPE into account. It includes a decision on how it will be verified in future.

For activities with a low risk under TRGS 400, TRGS 402 does not have to be applied. If activities are carried out in line with published process- and substance-specific criteria (VSK, TRGS 420), the employer can generally assume that the occupational exposure limits are met – a separate check by measurements or other methods is then not required (Section 7 (8) GefStoffV).

Measure, calculate or transfer: the assessment methods

• Workplace measurement

  Suitable forQuantitative determination of shift averages and short-term values

  Points to noteMeasurement strategy, suitable method, representative conditions

• Transfer from comparable workplaces or guidance (e.g. VSK, EGU)

  Suitable forActivities with comparable exposure conditions

  Points to noteResults for the reasonable worst case are particularly suitable

• Exposure models and control banding (e.g. EMKG-Expo-Tool, Stoffenmanager)

  Suitable forQuantitative or semi-quantitative estimates

  Points to noteInclude only technical and organisational measures, no PPE; check the result for plausibility

• Calculation models

  Suitable forIndicative estimates, e.g. from substance quantity and air change rate

  Points to noteJustify suitability in each case

Measurements are not always possible or meaningful – for example with very short exposure, where no suitable measurement method exists, in unfavourable climatic conditions or for certain outdoor work (TRGS 402 no. 4.4). Non-measurement methods help in these cases; both approaches can also be combined.

Finding, effectiveness and control measurements

The finding “protective measures adequate” requires that the general measures under Section 8 GefStoffV are in place, all assessment criteria including short-term values are met and this can be justified for the future too – for example by measurements under worst-case conditions, stable conditions or ongoing effectiveness checks. It can also be reached if a single representative measurement gives a substance or assessment index of up to 0.1, or three measurements in different shifts each give up to 0.25 and the short-term values are met. If the finding is “inadequate”, exposure-reducing measures and a new assessment are needed without delay; if the AGW is exceeded, the risk assessment must be repeated (Section 9 (3) GefStoffV).

• Substance or assessment index above 0.25 up to 1, or between acceptable and tolerable concentration

  Recommended control measurementevery six months

• Substance or assessment index up to 0.25, or up to the acceptable concentration

  Recommended control measurementannually

• Index below 0.1 with unchanged conditions (substances with an AGW)

  Recommended control measurementinterval of up to three years or justified omission

• Three consecutive control measurements below 0.25

  Recommended control measurementfurther control measurements may be omitted

You can also verify the finding through technical parameters such as the extraction air flow or continuous monitoring; with non-measurement methods, verification is due annually (TRGS 402 no. 6). A new evaluation is needed if conditions change, assessment criteria are revised or new measurement methods become available. Independently of this, technical protective measures must be checked for function and effectiveness at least every third year (Section 7 (7) GefStoffV).

Who may measure? Competence and accredited measuring bodies

Anyone carrying out workplace measurements must be competent and have the necessary equipment; anyone using other assessment methods must also be competent (Section 7 (10) GefStoffV). If you commission a measuring body accredited for hazardous substance measurements, you can generally assume that its results are correct. For non-accredited bodies, you must check yourself whether they meet the requirements of TRGS 402. Accredited measuring bodies are listed in the database of the German Accreditation Body (DAkkS). The technical measurement services of the accident insurance institutions also take measurements in companies – as part of their prevention mandate; their results do not replace the employer's risk assessment.

• Hazardous substances register and current safety data sheets
• Description of activities, quantities and the shift pattern
• Information on ventilation, extraction and other protective measures
• Notes on unfavourable conditions, such as peak load or summer operation
• Results of previous measurements and assessments

You should give these documents to the measuring body in advance. Under TRGS 402, measurement and finding should in principle be in the same hands, and the documentation must make every decision up to the finding traceable.

Checklist: meeting occupational exposure limits

• Activities with inhalation exposure recorded, including maintenance and cleaning
• Assessment criteria (AGW, TRGS 910, substance-specific TRGS) compiled for each substance
• Low risk or VSK under TRGS 420 checked
• Assessment method chosen, competent or accredited measuring body commissioned
• Shift averages and short-term values evaluated, substance and assessment index calculated
• Finding reached without PPE, justified and documented
• Control measurement plan or other verification defined
• Results recorded and made available to employees
• Technical protective measures checked at least every third year

Free templates for this guide

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

• Hazardous substances

  Exposure register template (Excel & PDF) under Section 10a GefStoffV

  PDF + ExcelFree download

Frequently asked questions