Lime / Hydrated Lime / Quicklime (CaO/Ca(OH)2)
COSHH assessment
A COSHH assessment for lime / hydrated lime / quicklime (cao/ca(oh)2) on a UK construction site: what it does to people, how it gets into them, the controls that stop it, the PPE for what is left, and what to do when it goes wrong. Copy it into your assessment and change what does not fit your job.
Hazards to health
Strongly alkaline (pH ~12.5), chemical burns to skin, eyes and respiratory tract. Quicklime (CaO) reacts exothermically with water, risk of steam burn and ignition of nearby combustibles. WEL 1 mg/m3 respirable, 4 mg/m3 inhalable for calcium oxide.
Routes of exposure
Skin contact, Eye contact, Inhalation
Control measures
- Hydrated lime preferred over quicklime where possible.
- LEV at silo and at mixing point.
- No water added directly to quicklime by hand.
- Wash facilities within 5m.
- Eye-wash station.
- Damp clean-up.
PPE for what is left
- Nitrile or neoprene gauntlets, Splash goggles plus face shield when handling quicklime, FFP3 mask, Coveralls, Wellington boots
Emergency procedures
- Skin: brush off dry product first, then irrigate 20 minutes, A&E.
- Eyes: irrigate 20 minutes minimum, urgent A&E (lime burns penetrate the cornea quickly).
- Inhalation: fresh air, A&E for breathing difficulty.
- Quicklime water reaction: evacuate area until cooled.
Questions people ask
Do I need a COSHH assessment for lime / hydrated lime / quicklime (cao/ca(oh)2)?
If the substance is hazardous to health and your work exposes people to it, yes. The Control of Substances Hazardous to Health Regulations 2002, regulation 6, require a suitable and sufficient assessment before the work starts, with the significant findings recorded if you employ five or more. The safety data sheet is an input to the assessment, not a substitute for it. Guidance, not legal advice.
What is the difference between a safety data sheet and a COSHH assessment?
The data sheet is the manufacturer describing the product in general. The assessment is you describing how your people use it on your job: how much, how often, for how long, in what ventilation, with what controls. Two firms using the same tin can have very different assessments.
What is a WEL?
A Workplace Exposure Limit, the maximum airborne concentration averaged over a reference period, set in HSE document EH40. For this substance: WEL 1 mg/m3 respirable, 4 mg/m3 inhalable for calcium oxide.
Is PPE enough?
No. COSHH puts PPE last: eliminate the substance, substitute for something less harmful, control at source with ventilation and enclosure, then organise the work to reduce exposure, and only then PPE for what is left. An assessment that jumps straight to gloves and a mask is the kind an inspector questions. Guidance, not legal advice.
How often should it be reviewed?
When the product, the method, the quantities or the people change, if there is any sign the controls are not working, and at least every year or so regardless. Health surveillance may be required where exposure could cause an identifiable disease, such as dermatitis or occupational asthma.
The COSHH assessment writes itself
Pick the substance in the SiteLynx RAMS editor and the COSHH assessment fills in with the hazards, controls and PPE, alongside the HAVS and noise assessments for the tools you chose. Signed on site on a phone. 14 days free.
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