One bad exposure can end a career
Two-pack (2K) polyurethane paints — common in vehicle refinishing and industrial coating — contain isocyanates in the hardener. Spraying creates a fine mist that, when breathed in, can cause respiratory sensitisation and occupational asthma. Once sensitised, even trace exposure can trigger an attack, and the worker can no longer work with isocyanates. The controls are an enclosed, ventilated spray booth and a supplied-air respirator — required in New Zealand when spraying isocyanate paint — plus health monitoring.
Isocyanates are hazardous substances found in the hardener of two-pack polyurethane paints used widely in automotive refinishing and industrial coating. Spraying produces a fine mist that can be inhaled deep into the lungs, causing respiratory sensitisation and occupational asthma. The danger is that once a worker is sensitised, even very low future exposure — or other triggers like cold air — can set off asthma symptoms, which can be severe and means they can no longer work with isocyanates. Anyone can be sensitised, not just people with a history of asthma. Skin contact can also cause sensitisation and dermatitis.
| Level | What it looks like |
|---|---|
| Eliminate / substitute | Use non-isocyanate paints where the job allows. |
| Process | Use spray techniques that minimise overspray, and keep other workers away from the spraying area. |
| Spray booth | A fully enclosed, ventilated booth that exhausts safely outside, kept maintained with filters changed on schedule. |
| Respiratory protection | A supplied-air (airline) respirator is required when spraying isocyanates — not a filter respirator. Keep the compressor air intake clean, and only remove the respirator outside the booth. |
| Skin & monitoring | Protective clothing and gloves, plus health monitoring for exposed workers. |
People with a history of asthma or eczema should seek medical advice before working with isocyanates.
The organic solvents and thinners used to clean spray guns can cause dermatitis through skin contact and affect the nervous system if inhaled, so they need managing too. Treat the whole task as hazardous-substances work — see hazardous substances — and back up the controls with the right respiratory protection.
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Isocyanates are hazardous substances found in the hardener of two-pack polyurethane paints, used widely in vehicle refinishing and industrial coating. Spraying them creates a fine, hazardous mist.
Breathing the spray mist can cause respiratory sensitisation and occupational asthma. Once sensitised, even very low future exposure can trigger severe asthma, and the worker can no longer work with isocyanates. Anyone can be sensitised.
A supplied-air (airline) respirator is required when spraying isocyanate paint in New Zealand — a filter respirator is not enough. Keep the compressor air intake away from contamination and only remove the respirator outside the booth.
Yes. Workers exposed to isocyanates should have health monitoring, which can include respiratory questionnaires and lung function tests, to detect early signs of sensitisation.
People with a history of asthma or eczema should seek medical advice before working with isocyanates, as they may be at greater risk, though anyone can become sensitised.
