Isocyanate Monitoring in Spray Painting – Sysco Environmental Ltd Case Study
Discover how Sysco Environmental Ltd monitored and controlled isocyanate exposure during spray painting at a UK fabrication site. Learn about the health risks, chemical use, and effective engineering controls that ensured safe working conditions.
How a Fabrication Facility Reduced Isocyanate Exposure to Undetectable Levels in Paint Spraying Operations
Sysco Environmental Ltd was commissioned to assess employee exposure to hazardous substances at a metal fabrication site in Cambridgeshire. A key focus of this assessment was the potential exposure to isocyanates used in the on-site spray painting processes. Employees were observed carrying out paint mixing, spraying, and clean-up activities using two-pack polyurethane paints, known to contain various diisocyanates.
The site operates a dedicated paint shop, equipped with a mixing station, spraying tables, and mechanical extraction systems. Employees were provided with air-fed respirators during tasks. This case study evaluates the airborne concentration of isocyanates, their use in paints, and outlines recommended control measures.
Understanding Isocyanates in Paints
What Are Isocyanates?
Isocyanates are a group of highly reactive chemicals used primarily in the production of polyurethane-based materials such as foams, coatings, adhesives, and paints. Common industrial isocyanates include:
Toluene Diisocyanate (TDI) – Used in flexible foam and spray applications.
Methylene Diphenyl Diisocyanate (MDI) – Common in rigid foams and potting compounds.
Hexamethylene Diisocyanate (HDI) – Widely used in automotive and industrial coatings.
Isophorone Diisocyanate (IPDI) – Used in high-performance paints and sealants.
Why Are Isocyanates Used in Paints?
Isocyanates are a key ingredient in two-component polyurethane paints, where they act as curing agents (hardeners). When mixed with a polyol resin, isocyanates initiate a cross-linking chemical reaction that produces a durable, chemical-resistant, and UV-stable coating.
This makes isocyanate-based paints ideal for:
Automotive and aerospace finishes
Structural steel coatings
Protective coatings for harsh environments
However, during spraying, airborne droplets or vapours can be inhaled or come into contact with skin, presenting serious health risks.
Health Effects of Isocyanates
Isocyanates are classified as respiratory sensitisers and are among the leading causes of occupational asthma in the UK.
Acute Exposure Effects
Eye and nose irritation
Throat inflammation
Coughing and breathlessness
Chronic Exposure Risks
Occupational asthma (often irreversible)
Long-term lung inflammation
Severe sensitisation: minute future exposures can trigger asthmatic reactions
Exposure may occur via:
Inhalation of overspray or vapours during spraying
Dermal contact with uncured paint or contaminated surfaces
Monitoring Methodology
Monitoring followed MDHS 25/3 guidelines for organic isocyanates in air. Personal and static samples were taken using piperazine-treated filters and analysed via high-performance liquid chromatography (HPLC).
Isocyanates Monitored:
Hexamethylene Diisocyanate (HDI)
Isophorone Diisocyanate (IPDI)
Methylenediphenyl Diisocyanate (MDI)
Toluene Diisocyanate (TDI)
Workplace Exposure Limit (WEL):
Long-Term (8-hour TWA): 0.02 mg/m³
Short-Term (15-min STEL): 0.07 mg/m³
Monitoring Results
| Location | Substance | 8-hour TWA (mg/m³) | WEL (mg/m³) | Result |
|---|---|---|---|---|
| Paint Shop (Sprayer) | HDI, IPDI, MDI, TDI | <0.000 (all) | 0.02 | Not Detected |
| Paint Shop (Mixing Station) | HDI, IPDI, MDI, TDI | <0.000 (all) | 0.02 | Not Detected |
Conclusion: All isocyanate levels were below the detection limit, indicating that the control measures in place (especially use of air-fed RPE) were highly effective.
Key Recommendations for Ongoing Risk Control
1. Ventilation
Status: Fixed extraction was functioning and serviced within the past year.
Recommendation: Maintain a 14-month service cycle. Fit airflow indicators on spray booths to allow users to verify performance instantly. Maintain a LEV logbook as per HSG258.
2. Respiratory Protective Equipment (RPE)
Status: Air-fed Versaflo M-107 units in use.
Recommendation: Maintain mandatory use of RPE for all spraying tasks. Provide clean storage for non-disposable units to avoid contamination. Train staff in RPE inspection and maintenance.
3. Health Surveillance
Status: No programme in place.
Recommendation: Implement a formal respiratory health surveillance programme in line with HSE asthma guidelines for isocyanate users.
4. Employee Training
Status: Informal only.
Recommendation: Deliver annual COSHH refresher training focused on:
Symptoms of respiratory sensitisation
Correct mixing and spraying procedures
Emergency response to RPE failure
Importance of consistent PPE use
Conclusion
Sysco Environmental Ltd’s assessment confirmed that isocyanate exposure during paint spraying operations at the Cambridgeshire facility is well controlled, with airborne concentrations below detectable levels. The use of air-fed RPE and functioning extraction systems plays a critical role in ensuring safety.
This case study illustrates the importance of:
Proactive exposure monitoring
Maintenance of engineering controls
Formalised health surveillance and training
OUR EXPERT
Tomas Gabor
0800 433 7914
Sysco Environmental Ltd are experts in isocyanate exposure monitoring across spray painting, coating, and polyurethane application processes. We provide air sampling, LEV evaluation, RPE strategies, and compliance reporting to help clients manage occupational asthma risks and maintain full COSHH and HSE compliance in high-risk paint environments.