The hazard
Hexavalent chromium: the hidden carcinogen in hot insulation
Chromium (VI) is not a contaminant that arrives on site. It forms in place, above 300 °C, where high-temperature insulation meets chromium-bearing steel — and it is usually hidden where no one can see it.
What hexavalent chromium is
Chromium (VI), or Cr(VI), is the most toxic oxidation state of chromium. In industrial settings the compounds of concern are calcium chromate and sodium chromate, which form when chromium in steel oxidises at high temperature in the presence of alkaline and alkaline-earth metals from insulation.
How it forms inside insulation
Above roughly 300 °C, chromium migrates out of the steel and reacts with calcium and sodium in the surrounding high-temperature insulation. The result is a chromate-bearing layer on and within the insulation — invisible, dust-forming, and easily disturbed during maintenance.
Why it is dangerous
Hexavalent chromium is a proven human carcinogen. Inhaling Cr(VI) dust is linked to lung and nasal cancer, and skin contact can cause ulceration and allergic dermatitis. Because the material is a fine dust hidden in insulation, workers can be exposed during routine maintenance with no obvious sign of a hazard.
The COSHH duty
Under the Control of Substances Hazardous to Health (COSHH) Regulations and the control of carcinogens, duty-holders must assess and control exposure to chromium (VI). Exposure must be kept as low as reasonably practicable and, for a carcinogen, actively reduced. You cannot evidence control of a hazard you have not measured.
Why testing is the only way to know
Chromium (VI) cannot be identified by sight. On-site rapid testing and accredited laboratory analysis are the only way to confirm whether it is present, where, and at what concentration — the evidence base for every decision that follows.
Common questions about chromium (VI)
What temperature does chromium (VI) form at?
Chromate compounds typically form above about 300 °C, where chromium-bearing steel meets high-temperature insulation containing calcium or sodium.
Is hexavalent chromium really a carcinogen?
Yes. Cr(VI) is classified as a category 1B carcinogen (H350, may cause cancer). Inhalation is linked to lung and nasal cancers, and skin contact can cause sensitisation and ulceration.
How do I know if my plant is affected?
The only reliable way is to test. We take on-site samples and breathing-air measurements and confirm the results in accredited laboratories.
What is the workplace exposure limit?
HSE EH40 sets an 8-hour time-weighted average of 0.05 mg/m³ for chromium (VI) compounds. As a carcinogen, exposure must also be reduced as far below the limit as reasonably practicable.
Can the hazard be removed permanently?
Yes. Substitution replaces chromate-forming insulation with alkaline-free materials, removing the hazard at source rather than managing it indefinitely.
Find out what you are dealing with
A site assessment turns an invisible risk into evidence you can act on, and a record that stands up to scrutiny.