Polyurethane (PU) Foam & MDI/TDI Sealants (isocyanates)
COSHH assessment
A COSHH assessment for polyurethane (pu) foam & mdi/tdi sealants (isocyanates) 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
Isocyanates are the leading cause of occupational asthma in the UK. Severe respiratory sensitisation, once sensitised, the worker cannot return to any isocyanate exposure. MDI WEL 0.02 mg/m3 8-hr TWA. Skin sensitisation. Cured foam dust also irritant.
Routes of exposure
Inhalation (aerosol/spray), Skin contact, Eye contact
Control measures
- Substitute with MS polymer or silicone where possible.
- Cartridge gun foams produce limited aerosol, manageable in well-ventilated areas.
- Spray-applied PU (e.g.
- spray foam insulation, 2K coatings) requires forced ventilation plus airfed RPE, no half-mask is adequate.
- Confined spaces: airfed only.
- Mandatory pre-employment and annual health surveillance with respiratory questionnaire and lung function.
- Permanent removal from exposure on first sign of sensitisation.
PPE for what is left
- Spray application: airfed full-face hood/visor (TH3).
- Cartridge foam in ventilated area: A2P3 half-mask minimum.
- Nitrile gloves (laminate for spray), Splash goggles, Type 5/6 coveralls
Emergency procedures
- Inhalation: fresh air, 999 if wheeze or chest tightness.
- Symptoms may be delayed up to several hours and worsen with each exposure.
- Skin: wash thoroughly with soap and water.
- Eyes: irrigate 20 mins, A&E.
- Report all exposures to occupational health for biological monitoring.
Questions people ask
Do I need a COSHH assessment for polyurethane (pu) foam & mdi/tdi sealants (isocyanates)?
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 0.
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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