Understanding chromium(VI)

On insulated hot parts and in incinerators, Chromium(VI) forms in operation. It is released during maintenance.

Basic oxides in insulation materials or in the combustion material react above about 300 °C with the chromium present to form calcium and sodium chromate. Removal, cleaning, overhaul and dismantling are affected.

What to do now Read the expert analysis

Don’t give Chromium(VI) a chance!Detect | Control | Prevent

Maintenance on a CHP gas engine with chromium(VI) on insulated hot parts

Maintenance on a combined heat and power plant. The insulation lies on chromium-alloyed steel.

The current position

0.005 mg/m³

binding EU occupational exposure limit value for chromium(VI) compounds, since 18 January 2025

Directive 2004/37/EC, Annex III Part A

1 µg/m³

binding limit value in the Netherlands and France and the value applied in Germany; one fifth of the EU value

NL: Arboregeling, Annex XIII · FR: Code du travail, Art. R. 4412-149 · DE: TRGS 561, 3.3.4(2)

11 April 2025

Annex XV restriction proposal submitted to ECHA

Maintenance on insulated hot parts is not exempted

Inhalation

Breathing in chromate dusts during maintenance, opening, dismantling, cleaning or handling

Directive 2004/37/EC, Article 3(2) and (3)

Skin

Absorption into and through the skin is to be taken into account in the risk assessment. There is no limit value for the skin route, and an air measurement does not cover it.

Directive 2004/37/EC, Article 3(3)

Ingestion

Hand-to-mouth transfer via hands, objects, food or drink

Directive 2004/37/EC, Article 3(2) and (3)

Environment

Calcium and sodium chromate are very toxic to aquatic life with long-lasting effects. Waste, residues and water bodies are affected.

H400, H410, Regulation (EC) No 1272/2008, Annex VI

An air measurement below the limit value does not lift the protective regime for carcinogens as long as settled chromate-containing dusts and fibres can be stirred up at any time or skin contact is possible. It covers only the inhalation route and only the conditions during the measurement.

Directive 2004/37/EC: the duties under Articles 3, 4 and 5(1) to (3) do not depend on whether the limit value is reached

United Kingdom. Since 1 January 2021 the United Kingdom is no longer bound by Directive 2004/37/EC. The COSHH Regulations 2002 apply. EH40/2005 sets a workplace exposure limit for chromium(VI) compounds of 0.01 mg/m³ as an 8-hour TWA and 0.025 mg/m³ for process-generated chromium(VI). Regulation 6(2)(e) names maintenance with the potential for a high level of exposure as a subject of the assessment.COSHH Regulations 2002, Regulation 6 · EH40/2005

From 1 December 2026 Australia no longer sets an occupational exposure limit for chromium(VI) compounds. It is replaced by the duty to eliminate exposure or minimise it so far as is reasonably practicable (SFAIRP, comparable to the ALARP principle).Safe Work Australia, Workplace exposure limits for airborne contaminants, in force from 1 December 2026

Fields of work

Five fields, one set of facts

Chromates form in situ where chromium-alloyed hot parts are in contact with alkali and alkaline earth metal oxides during operation. These oxides come from the insulation, where formation starts at about 300 °C, or from ash and combustion residues on grates and hot part surfaces. In waste incineration, chromium(VI) compounds form in particular when the plant is shut down and the grate and ash residues cool with access to oxygen, and in direct desulphurisation with calcium hydroxide or limestone powder. The chemical process is the same in all five fields; what differs are the plants and the activities during which the chromates are released.

Occupational safety

Risk assessment, risk concept, list of exposed workers

Chromate expertise

Formation pathway, sampling and analysis

Chromate remediation (CHP, power generation, waste incineration)

Removal, decontamination, disposal

Thermal insulation (substitution)

Oxide composition as a procurement criterion

Incineration ash (decontamination)

Chromates in ash and boiler deposits

Chromate expertise

The finding forms at the interface

Yellow calcium chromate on the textile insulation of a CHP engine

In the delivered state no chromate is present. It forms at the interface between insulation and component and forms again after every start-up. Which compound forms depends on the oxides in the insulation.

Mineral wool carries Na₂O and CaO; sodium and calcium chromate form
Calcium silicate and AES wools carry a high proportion of CaO
E-glass fabrics and needle mats carry CaO in a lower proportion
Chromate analysis with SEEF equipment, sampling and evaluation

Colorimetric quick tests miss chromium(VI) that the laboratory detects. A negative test does not lift the duties.

Chromate remediation

Removal, decontamination, disposal

Remediation begins with the removal of the thermal insulation and ends with the proof of disposal. In between lie low-dust working, enclosure, personal protective equipment and the documentation of exposure.

Chromate remediators in the network: Kavarmat® and The Chromate Experts UK Ltd.
Removal of thermal insulation as part of the scope of work
Chromate disposal through MRP, Effinowicz Group

Chromate remediation of a CHP engine, worker in protective suit

Preparing chromate remediation on a CHP engine, contamination control with foil

CHP engine after substitution of the thermal insulation

Before: preparing chromate remediation on a CHP engine (contamination control). After: successful substitution of the thermal insulation.

Incineration ash

Chromates in ash and boiler deposits

Waste incineration brings the oxides and the chromium-alloyed steel together in the same plant. Incineration ash containing chromium(VI) is a field of its own, with its own questions on sampling, classification and disposal route.

Expert analyses

The two works on cr6.info

Expert analysis · Version 1.11

The Overlooked Ingredient

Chromium(VI) from thermal insulation (high-temperature insulation) and in combustion ashes.

Read on cr6.info

Expert analysis · Version 0.18

The Overlooked Use Ban

Reinstalling chromate-contaminated mineral wool as an authorisation-required use (REACH) of the chromium(VI) compound sodium chromate.

Read on cr6.info

For download

Press releases and technical notes

PressChromium(VI) in hospital engineering05.10.2026

PressChromium(VI) on exhaust components05.10.2026

NoteChromium(VI) in plant operationOct 2026

NoteChromium(VI) during maintenance on CHP and cogeneration plants02.10.2026

NoteChromium(VI) on vehicle exhaust components03.10.2026

NoteChromium(VI) in waste incineration plants03.10.2026

Blog

From practice

PostChromium(VI) in incineration ash: two decontamination jobs in Warsaw and Krakow29.10.2026

Manufacturer notices

The manufacturers have been writing it for years

Notices on the formation of Chromium(VI) on insulated hot parts have been updated since November 2020. They concern exhaust systems, turbochargers, heat shields, steam turbines and insulated pipework.

WS00Q563Wärtsilä

8339SMMAN Truck & Bus, Service Information

SI00.10-P-0054AMercedes-Benz

NTS 559Rolls-Royce

2175/00Caterpillar, Technical Bulletin

TechInfo 28Frenzelit, August 2025, four conditions for formation

ProRox WMRockwool, 1 January 2025, more than 18 per cent by weight of basic oxides

The network

The Chromate Experts

A network with members in Germany, Switzerland and the United Kingdom. It deals with the formation of Chromium(VI) compounds on thermally stressed chromium-alloyed components in industry, power generation, shipping and vehicle engineering.

The network

Members and partners

Markus SommerInitiator, The Chromate Expert
Stephan EffinowiczChromatexperten Effinowicz GmbH
Lloyd HopesThe Chromate Experts UK Ltd.
Kavarmat®Chromate remediation and removal
MRPChromate disposal, Effinowicz Group
Chromatexperten CHSafetyMax AG, Switzerland