Gas Clearance & Hazardous-Substance Measurement Expert
Gas clearance of tanks and confined spaces plus workplace exposure measurements against the AGW. Appointed as a competent person before entry permits are issued under TRGS 402.
TRGS 402 · DGUV Regel 113-004
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What does a Gas Clearance and Measurement Expert do?
A competent person for gas clearance and hazardous-substance measurement assesses airborne contaminant concentrations at the workplace and clears tanks, vessels and confined spaces before entry. The work is governed by the Hazardous Substances Ordinance (Gefahrstoffverordnung, GefStoffV) and operationalised by Technical Rule TRGS 402, which sets out how to identify and assess inhalation exposure and how to compare results against the occupational exposure limit (Arbeitsplatzgrenzwert, AGW). For confined spaces, DGUV Regel 113-004 describes the measurement, ventilation and entry-permit regime.
Before an entry permit is issued, the expert measures oxygen content, flammable gases against the lower explosion limit and toxic substances against their AGW, then documents that the atmosphere is safe (Freimessen). For routine operations they plan and carry out workplace exposure measurements following the measurement strategy of TRGS 402, select sampling positions and durations, and decide whether the exposure assessment confirms compliance or requires further protective measures under the GefStoffV.
The expert reports results to the employer so the risk assessment (Gefährdungsbeurteilung) under Sec. 6 GefStoffV can be updated, advises on substitution, ventilation and personal protective equipment, and ensures measuring devices are calibrated and functionally tested. Where carcinogenic substances are involved, TRGS 910 and the risk-based concept of acceptance and tolerance concentrations apply. The aim is a documented, defensible basis for permitting entry and protecting workers from inhalation hazards.
Core duties of the measurement expert
- Plan exposure measurements using the measurement strategy of TRGS 402 and define sampling points and durations.
- Carry out gas clearance (Freimessen) of tanks and confined spaces before entry permits are issued.
- Measure oxygen, flammable gases against the lower explosion limit and toxic substances against the AGW.
- Compare results with the occupational exposure limit (AGW) and assess compliance under the GefStoffV.
- Apply DGUV Regel 113-004 for confined-space measurement, ventilation and permit requirements.
- Calibrate, bump-test and maintain gas detectors and sampling equipment before each use.
- Document measurement results and clearance certificates as evidence for the entry permit.
- Feed findings into the employer's risk assessment under Sec. 6 GefStoffV and recommend protective measures.
- Apply the acceptance and tolerance concept of TRGS 910 where carcinogenic substances are present.
- Brief entry teams and permit issuers on the meaning of the measured values and re-measurement intervals.
When is a competent measurement person required?
TRGS 402 and the GefStoffV require that exposure measurements and assessments are carried out by a competent person (fachkundige Person) who has the training, experience and current knowledge to select the right method, perform the measurement and interpret the result. The employer remains responsible under Sec. 6 GefStoffV for the risk assessment but must draw on this competence whenever inhalation exposure cannot be reliably excluded.
For confined-space work, DGUV Regel 113-004 makes gas clearance by a competent person a precondition for the entry permit: vessels, tanks, shafts and silos may only be entered after the atmosphere has been measured and documented as safe. The competence is typically evidenced through recognised training as a measurement expert plus practical experience with the relevant substances and devices. Where an accredited measurement is required, for example to demonstrate AGW compliance to the authority, a measuring body accredited under the relevant standard may need to be engaged. The expert must also stay current as exposure limits in the TRGS series and the AGW list are updated.
- Entry into tanks, vessels or confined spaces requiring a permit
- Inhalation exposure that cannot be excluded under Sec. 6 GefStoffV
- Workplace exposure assessment required by TRGS 402
- Confined-space work governed by DGUV Regel 113-004
- Handling of carcinogens under the TRGS 910 risk concept
- Authority request for proof of AGW compliance
Sectors that need measurement experts
- Chemical and petrochemical plants
- Tank and vessel cleaning services
- Water and wastewater utilities
- Shipbuilding and tank construction
- Pharmaceutical production
- Foundries and metal processing
- Biogas and energy plants
- Confined-space and industrial maintenance
- Painting and coating operations
How CIVAC supports the measurement expert role
CIVAC turns measurement and clearance work into a controlled, documented process. Task templates cover device calibration, bump tests, exposure-measurement campaigns and gas-clearance checks, each with reminders before the next due date. Clearance certificates, sampling records and AGW comparisons live in the documentation area, linked to the relevant permit, so the basis for every entry decision is retained. The audit trail records who measured what and when, which supports the employer's risk assessment under Sec. 6 GefStoffV during a labour-inspection review. The training library keeps competence current as the TRGS series and the AGW list change. EU data residency keeps measurement evidence inside the jurisdiction the GefStoffV applies to.
Frequently asked questions
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