Guidance on working with 2-pack isocyanate paints


Paints containing isocyanate are used extensively in MVR as almost all motor vehicle repair bodyshops use 2-pack or "2K" isocyanate-containing paints. Isocyanates are used in some water-based paints, most base coats and almost all lacquers.  'Water-based' does not mean 'isocyanate-free', just that it is emulsion based and has reduced levels of solvents.

Spraying 2-pack isocyanate paints is the main cause of occupational asthma in the UK and, for years, vehicle paint sprayers have been the group most at risk. MVR paint sprayers have about a 90 times higher risk of getting asthma compared with the UK working population. Every year around 50 sprayers are diagnosed with isocyanate asthma and most have to leave the industry. Other workers in bodyshops are also sometimes affected eg maintenance personnel, managers and others who work in close proximity to spray booths/rooms. This spray mist containing isocyanate may also worsen existing asthma. Once people are affected even very low exposure levels can trigger an attack. Significant skin contact with isocyanate hardeners may cause dermatitis.

Over a number of years HSE have worked with industry representatives to explode the myths and explain why even the best air-fed visor can fail to protect people. Over 2000 people involved with vehicle paint spraying have attended free workshops up and down the country to find out how they could carry on using isocyanate paints safely. The ground-breaking training material used at these Safety and Health Awareness Days has now been made freely available on the MVR webpages.

Below are some key tips for vehicle paint sprayers and owners of motor vehicle repair bodyshops.

Vehicle paint sprayers

  • The risk of developing occupational asthma occurs because paint spraying produces a lot of invisible airborne mist that you can breathe in. Never spray paint outside the booth or room.
  • Your booth/room takes time to clear of mist, so know the clearance time and make sure everyone else does too.
  • Always wear air-fed breathing apparatus (BA) when spraying and know how to safely leave or enter your booth or room during the clearance time.
  • Your employer should check the controls are working by measuring your exposure to isocyanate. Currently the only way to do this (and accepted by the MVR industry) is by providing a urine sample for analysis. See Sector Information Sheet 03/2012/01 - Reducing ill health from isocyanate exposure in motor vehicle repair (MVR)
  • You need regular health surveillance ie lung function testing and skin checks. This is to identify early symptoms and signs of occupational asthma and dermatitis (skin rashes).

Bodyshop owners / managers

  • Spraying 2-pack isocyanate paints creates fine, invisible, airborne mist that can cause occupational asthma
  • It spreads through the air like smoke.
  • Your spray booth or room takes time to clear of fine paint mist.
  • Measure the clearance time using a smoke/fog generator, clearly mark it on the entrance door(s) and make sure everyone who uses the booth/room knows what to do. For information on smoke generators and advice on how to conduct a clearance time measurement please see 'Measuring paint spray booth clearance time'.
  • The research report 'An automated system for indicating spray clearance times of MVR spray booths and rooms - RR742' describes the design and assembly of a device consisting of a timer switch, programmed with the clearance time, which is triggered by a sensor that detects when the spray gun is turned on and off. Two types of sensor are evaluated and recommendations made for different operational setups. The system is relatively inexpensive and can be retrofitted to existing spray booths/rooms.
  • Make sure the booth/room runs at slight negative pressure so that if there are any leaks, air is drawn into the booth/room rather than paint mist leaking out into the workshop
  • Make a list of simple daily and weekly checks to be done in the booth/room, appoint someone to do them, record the findings and act if things are wrong
  • Check exposure is properly controlled by arranging for the analysis of urine samples of vehicle paint sprayers. See Sector Information Sheet 03/2012/01 - Reducing ill health from isocyanate exposure in motor vehicle repair (MVR)
  • Arrange regular health surveillance for those potentially exposed to isocyanate paints such as sprayers. For more information on health surveillance for occupational asthma see HSE guidance publication 'Health surveillance for occupational asthma (G402)'
  • Use the COSHH paint spraying and allied tasks and other published advice to help you reduce exposures to isocyanates.

Further information

Case studies

  • When workers in a large bodyshop complained of paint smells and tight chests, HSE measured their isocyanate exposure by biological monitoring. It was found that everyone in the bodyshop was exposed to isocyanate. The most highly exposed person being the receptionist. The downdraft spray booth filters were clogged and the over-pressure sensor had failed. The booths were becoming pressurised, especially during baking, and were leaking badly. They had never been thoroughly examined or tested.
  • An MVR paint sprayer worked for 10 years painting commercial vehicle bodies. He worked in a spray space and wore air-fed breathing apparatus. However, after spraying he would routinely flip up his visor to check on paint coverage, quality etc allowing no time for the fine (invisible) overspray mist to clear. The first indications that something was wrong was when he started to suffer a tight chest overnight. Neither the sprayer nor his GP made the connection between his asthma and exposure to isocyanates at work. He soldiered on until he could no longer work. Effectively he was unemployable because he was unable to walk more than 20 yards before he needed to stop and rest.
  • A motor mechanic wore an ori-nasal filtering half-mask respirator when he started using 2-pack isocyanate paints in a spray space. Within a few months he found he was wheezing in the evenings after work and had a cough. He thought he was getting flu. After two years he had an acute asthma attack and was hospitalised. He is now registered disabled and is a respiratory cripple. He gets asthma attacks triggered by non-specific air contaminants such as the smell of gloss paint or diesel fume or even just cold air.
  • A small bodyshop spraying isocyanate paints constructed its own spray room without help or advice from a specialist, such as a ventilation engineer. Not only did the sprayroom leak into the adjacent vehicle preparation areas, it also contaminated the air in the factory unit next door. HSE prohibited the process. The business ceased to trade.

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Updated 2022-11-09