This Note refers to paints in which an organic isocyanate has been used as a constituent, or is added as part of a two-pack system.

The special properties of such paints depend upon the reaction between this isocyanate and a substance providing hydroxyl groups or other reactive hydrogen atoms. In some cases, the substance may be water vapour in the atmosphere. As with all paints, precautions have to be taken when spraying them, but there are hazards peculiar to these polyurethane paints arising from the use of the isocyanates. Unless proper precautions are taken, there is a potential hazard from the isocyanates because they are respiratory sensitisers.

A sensitised person will react to very low concentrations of isocyanates. Symptoms of chest tightness or wheezing may occur, but there is rapid recovery when ceases. Observation of the following recommendations, together with good standard of industrial hygiene will enable paint products containing isocyanates to be used without risks to health.

1. Selection
   • Persons with a history of asthma should not be engaged in any process, which involves the use of isocyanates. Firms engaged in spraying products containing isocyanates are advised to have spray operators medically examined before employing them in this work. Persons showing adverse symptoms should obtain medical advice immediately.
2. Plant Design
   1. Spray operations involving products containing isocyanates should be carried out preferably in suitable spray booths or enclosures under effective exhaust ventilation so that the spray-mist cannot enter the spray operator's breathing zone or escape into the general workroom atmosphere outside the spray booth.
   2. The exhaust ventilation should be designed so that spray-mist is conducted away to a safe place.
   3. Air-flow velocities should be sufficient to disperse spray-mists and vapours effectively. Normally an air-flow velocity of 1 metre per second may be considered sufficient.
3. Personal Protection
1. When operators, whether spraying or not, have to work inside the spray booth, they should wear compressed airline breathing apparatus - BS4667:Part 3: 1974 - or other air-fed equipment which provides equivalent protection both during the spraying process and until such time as the spray-mist has cleared.
2. The design of equipment used you supply compressed air to the breathing apparatus should conform to BS4275: 1974. In particular, care should be taken to ensure that the supply of air to the compressor is drawn from an uncontaminated source and that an efficient oil / water and fume filter is fitted to provide respirable air. Where operators are required to work within the booth an alarm system should be fitted to warn the user of the apparatus whenever the air pressure falls to the minimum safe working level.
3. Persons entering the spray booths or enclosures for short periods (Less than 15 minutes) when spraying is taking place may be protected from inhaling the spray-mist by wearing suitable respirators to BS2091: 1969 with type CC canisters. Care should be taken to ensure that filters are changed when necessary.
4. Airline breathing apparatus is not essential during short periods of spraying polyurethane paint products on small test panels in quality-control booths. However, an inward air velocity at the face of the booth of not less than 1 metre per second should be provided and a canister respirator to BS2901 should be worn.
4. Spillage
   • Accidental spillages should be absorbed on to sand or earth or other inert material. Waste materials collected in this way should be disposed of in accordance with the Deposit of Poisonous Waste Act, 1972. DO NOT ALLOW the materials to enter any drains
5. Fire
   • Most of the products covered by this Note are subject to the requirements of the Highly Flammable Liquids and Liquefied Petroleum Gases Regulations, 1972, and must be handled and stored accordingly. In the event of fire, fight with foam and take suitable precautions against inhaling combustion products.

Bibliography

BS4275: 1974 - Recommendations for the selection, use and maintenance of respiratory protective equipment.
BS2091: 1969 - Respirators for protection against harmful dust, gases and scheduled agricultural chemicals.
BS4667: Part 3: 1974 - Fresh-air hose and compressed air line breathing apparatus.

Obtainable from regional sales offices of BSI; orders by post should be addressed to: BSI Sales Department, 101 Pentonville Road, London, N1 9ND. Deposit of Poisonous Waste Act, 1972 - Highly Flammable Liquids and Liquefied Petroleum Gases Regulations, 1972. SI 1972, No. 917. Obtainable from HMSO.

This Technical Data Note has been prepared with the assistance of the Paintmakers Association of Great Britain Ltd, and the Health and Safety Executive.