Safely spraying isocyanate paints

Problem

Spraying motor vehicles and other surface types with two-pack polyurethane paints containing isocyanates, for example polyisocyanates, presents a risk to employee health.

Risks

Spraying generates a mist that may be inhaled and cause respiratory sensitisation and occupational asthma.

Once a person is sensitised, exposure to trace amounts of isocyanates can trigger asthma symptoms, which means the person can no longer work with isocyanates.

Organic solvents and thinners used to clean spray guns can also cause dermatitis through skin contact and affect the central nervous system and other organs through inhalation.

Solutions

The following solutions can help to eliminate or reduce the risks:

• Work with non-isocyanate-containing paints.
• Use spray techniques that minimise overspray.
• Use a fully enclosed spray booth that vents safely outside and ensure that:
  • air velocities for down-draught and side-draught booths are a minimum of 0.25m/s and 0.5m/s respectively
  • the booth is run for at least 5 minutes after spraying to allow spray mist to clear
  • the spray booth is regularly checked, tested and maintained (including replacing filters) in accordance with manufacturer’s recommendations
• Use a full-face airline respirator when spraying isocyanates. Disconnect and remove the respirator outside the booth. Maintain respirator air quality by:
  • checking that the compressor air intake is located away from sources of contamination such as motor vehicle exhaust fumes
  • replacing consumable filters, such as particulate, coalescing and charcoal filters, in accordance with manufacturer’s recommendations
  • keeping records of compressor and filter system servicing and maintenance

Make sure that:

• colour matching is carried out under local exhaust ventilation (LEV)
• spray guns are cleaned using an automated gun wash system or under LEV
• suitable gloves are worn if skin contact with 'gunwash' solvent is likely. Refer to the safety data sheet to ensure the correct gloves are used
• lids are placed on open containers of thinners and solvent soaked rags to prevent unnecessary exposure to solvent vapours
• ignition sources are eliminated where flammable solvents are used or stored
• paints and thinners are stored properly — use flammable liquids storage cabinets for small quantities or a designated storage room with adequate ventilation, bunding and intrinsically safe lighting)
• health surveillance is provided, including lung function testing under the supervision of a doctor