What spray painters must know about two-pack paint spraying

ITW Finishing Technologies
Thursday, 24 February, 2011


Two-pack paint includes various types of polyurethane, epoxy and acrylic systems, consisting of a base component, in combination with a hardener or catalyst. Quite a toxic concoction that can cause a series of health issues; therefore, two-pack paint is only to be applied by those people with appropriate knowledge and training.

The hazards associated with spray painting typically occur during three key work stages:

  • Preparation including job set-up, paint and surface preparation, mixing and pouring;
  • Use of two-pack paint systems; and
  • Clean-up.

Hazardous-air pollutants (HAPs) are commonly found in most automotive paints, primers and clear coats. They can be the cause of:

  • Asthma, heart attacks, bronchitis, premature mortality (particulate matter);
  • Asthma and bronchitis (volatile organic compounds);
  • Neurotoxicity, lung cancer (hazardous air pollutants - toxics, including lead, chromium and cadmium);
  • Occupational asthma; skin and lung sensitisation (diisocyanates);
  • Irritation, headache, nausea, liver, kidney, nervous system damage (solvents); and
  • Sensitisation; in effect becoming allergic to the paint.

People working in the spray painting industry must understand the risks that different substances create and always consider the following:

  1. How the substance could enter the body and affect health - inhalation, ingestion, absorption and injection. Surface preparation can create dusts containing substances such as lead and carbon fibres. Pouring liquids from one container to another could release toxic vapours. Inhalation of vapours and aerosols, injection by high-pressure equipment, skin contact and absorption are the most likely ways substances used in spray painting can enter the human body. The MSDS of a substance and labels will provide the basic information about possible short- and long-term health effects and recommend protective measures amongst other things.
  2. Consider how many other people are in an area where they could possibly be exposed. These could be contractors, visitors or suppliers.
  3. Typically, how often and for how long might all or some of the employees be exposed? The outcome of this assessment factor will also depend on what measures are currently being used to prevent exposure.
  4. The size and shape of the object being worked on, but most importantly the location of the object in relation to the painter and other people are to be considered. The direction of the stream of ventilating air is crucial in assessing risks. Direction of airflow has a significant effect where the overspray blows back to the operator or is directed towards other people in the vicinity.
  5. Work practices resolving the issue of how to effectively isolate people from the spray hazards, ventilation, PPE - everything from preparation to the final clean-up stage.

Observations of common practices in spray painting indicate that poorly chosen and the inappropriate use of PPE are factors contributing to unnecessary exposure to hazardous substances.

PPE is an essential part of reducing risks and should be used as an additional measure to booths. First of all, the PPE used should be in line with the recommendations on the MSDS. Consultation with the PPE supplier can also assist in matching the most appropriate equipment to the spray painting jobs at hand, proper fit, correct use and maintenance of the equipment.

Too many businesses often don’t use standard methods for painting, and they don’t comply with accepted industry practices or current control technologies. Only through implementing best practices can toxic exposures be controlled.

Spray painting, whether in outdoor or indoor environments, needs to be performed in a safe manner, and as this might be somewhat difficult to manage outside, it is probably best to apply the paint with rollers.

Two-pack paint spraying is best to only occur within a spray booth, restricting air movement eg, via ventilation ducts and air-conditioning vents into occupied areas of a building. Fans should be available to exhaust contaminated air outside the building and adequate fresh air should be supplied if needed.

Additionally, appropriate PPE should be worn, comprising:

  • Full protective clothing, such as disposable coveralls. Any remaining exposed skin should be coated with barrier cream, as these paints stick very well.
  • Nitrile or butyl-rubber gloves must be worn as they provide protection from a variety of chemicals, as opposed to latex gloves.
  • An airline respirator is required for spraying two-pack polyurethane. If an airline respirator is not available when applying two-pack epoxy or acrylics, a full-face air-supply respirator (ie, battery-operated filter unit) fitted with organic vapour cartridges (type A class 2, or type AX or A + K, class 2) with a pre-filter, may be used for short periods of time. However, this filter-type respirator is not suitable for paints containing isocyanates. A full-face piece that also provides eye protection is required to prevent absorption of mists and vapours through the eyes. If paints containing isocyanate are used, filters must be changed regularly, or immediately when solvent smell can be detected.

An air-purifying respirator is only as good as its filter change schedule, which can be a challenging process. The best way to overcome this challenge is to wear positive pressure supplied air respirators. Spray painters are much less likely to breathe harmful chemicals, as these systems tend to be a more user-friendly option when it comes to monitoring the equipment.

It is advisable to follow the inspection schedule in the AS 4114.1-1995 ‘Spray Painting Booths, Part 1: Design, construction and testing’ standard. Also refer to AS/NZS 1715:2009 for more information on selection, use and maintenance. Also, check information and guidelines issued from safety regulators and other sources such as ANU, OSHA and EPA.

In the US, the EPA’s new NESHAP 6H rule resulted in a two-year collision-repair campaign, in recognition of the range of health and environmental issues from collision-repair activities. Two-pack paint is the same everywhere in the world and the same best practices apply.

Supplied-air respirators are a proven safety solution when clean compressed air from a source outside the contaminated area is needed. Air passes through an airline to the face-piece or hood, with the continuous flow creating increased pressure inside. This pressure cools the user’s face and reduces fogging, a common problem in many working situations. The user’s airways, face, neck and head areas are totally protected.

All respiratory equipment must be supplied with air filtered to 0.01 microns using a coalescing filter.

By Richard Hoagland, General Manager, ITW Finishing Technologies

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