Resene Paints - home page

Polyurethane paints and lacquers

From the putting your safety first section

Polyurethane paints and lacquers fall into the following three categories:

1 Urethane oils and urethane alkyds (e.g. polyurethane varnishes):

Urethane oils and alkyds contain no residue of free unreacted isocyanate and thus the handling and use of these products is no different to normal solventbased paints.

2 Blocked isocyanates (e.g. some soldering fluxes):

Blocked isocyanate coatings also contain no residue of free unreacted isocyanate, and thus the application of these materials poses no problems from that viewpoint. However, phenolic solvents may be present in the formulated paint and additional phenolic material may be released during heat curing processes. In these circumstances appropriate precautions for phenols must be taken. These must include protection (adequate ventilation and/or respiratory protection against inhalation of phenolic containing vapours and suitable protective clothing to prevent skin contact).

3 Polyisocyanates (e.g. one pack moisture-cured and two-pack isocyanate containing paints):

The great majority of industrial-used polyurethane coatings contain polyisocyanates. This section is concerned with precautions to be observed in the handling and application of these materials.

The two most important isocyanates are toluene diisocyanate (TDI) and 4.4.1 diphenylmethane diisocyanate (MDI).


Application by brush or roller:

Application by spraying:


Precautions to be adopted for spraying and drying of sprayed articles:

  • All spraying and the drying of sprayed articles shall be carried out in accordance with the requirements of the Regulations.
  • The spraying of all isocyanate-containing paints must be carried out in a properly designed and constructed spray booth.
  • The mechanical ventilation system provided must be interlocked with the air supply to the spray gun.
  • When operators, whether spraying or not, are required to work inside a spray booth whilst spraying is in progress, they shall wear an airline respirator.
  • The compressed air supply for the respirators must be taken from an uncontaminated source.
  • In addition to the recommended respiratory and eye protection, spray operators shall wear gloves and a head covering in the case of respirators which leave the hair exposed.
  • Mechanical ventilation of the booth must be maintained after spraying ceases until the work area is free of all residual spray mist.

Isocyanate over-exposure:

Symptoms include:

First aid treatment:

Removal of polyurethane paint:

Sanding down:

When isocyanate paints are fully cured, if they have been applied for more than 24 hours at room temperature or heated for one hour at 70°C, and are sanded down, the dust produced will not present an isocyanate hazard. This is because fully cured paints contain no free isocyanates. In such instances a dust mask should be worn to provide protection from the general nuisance dust present. Where new paint that may not be fully cured is sanded down, the dust will contain free isocyanates.

A particulate respirator fitted with Class H filters should be worn. Where practical, the use of wet sanding methods is recommended as a means of reducing the amount of dust generated.

Personal hygiene:

This is important in any industry where harmful chemicals are used. The basic rules are common sense:

The employer's responsibilities:

The employer must instruct workers on the hazards of working with isocyanate-containing paints and how to use them safely.

The employer is also legally required to provide all the necessary safety equipment.

The employee's responsibilities:

Employees have a duty to use all the safety gear the employer provides. Employees owe it to themselves to protect their health – and the job they have spent years learning.

Spillage procedure:

  1. Put on protective equipment.

  2. Cover spillage with absorbent material such as sawdust.

  3. Pour on decontaminant mixture, a quantity estimated to be twice the volume of the spill. Refer to 'Approved Code of Practice of the Safe Use of Isocyanates'.

  4. Allow at least 10 minutes for the decontaminant to react.

  5. Collect all residues from the spillage and place them in an open container.

  6. Add further decontaminant mixture to this material, place a loose cover over the container and remove it to a safe place. Discard residues after one day.

  7. Wash down the area with liquid decontaminant.

  8. Rope off the area and post 'No Smoking' signs.

  9. Clean and decontaminate safety equipment.

Further information:

For further information refer to ‘Approved Code of Practice for the Safe Use of Isocyanates’ published by the Occupational Health and Safety Service, Department of Labour, Wellington.

Related booklets available from OSH:


Putting your safety first!
Understanding paint hazards and essential precautions

Safety topics   Problem solver topics   Ask a Paint Expert


Get inspired!  Sign up for our e-newsletter  |  Get saving!  Save with a Resene DIY card

Resene Paints Ltd

Can't find what you're looking for? Ask us!

Resene Paints Ltd   –

View Videos

Colours shown on this website are a representation only. Please refer to the actual paint or product sample. Resene colour charts, testpots and samples are available for ordering online.   See measurements/conversions for more details on how electronic colour values are achieved.