Question: A caller from West Virginia was worried about free isocyanates being released from epoxy paint applied in a poorly ventilated area. The label says that the paint takes seven to 14 days to cure properly. How long should one wait before re-entering the work area after the paint is applied?

 

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Answer: The isocyanates in epoxy paint are dimmers or longer polymers and are not gasses. In addition, the isocyanates act as a catalyst so that in the application process, all of the isocyanates react almost instantaneously to form the epoxy resin. The shorter the isocyanate polymer, the more quickly it will react. As a result, there are no free isocyanates in the paint after it is applied that could volatilize during the curing process. Thus, no adverse health effects are expected following the proper application of the epoxy paint. However, during the curing process, the solvent in the paint will continue to evaporate (gas off) as the paint hardens over the next several days.

 

The amount of solvent that evaporates decreases over time so that under "standard conditions," i.e. a temperature of 68 degrees F and a relative humidity of 50 percent, the workers should be able to safely enter the work area after two to four hours. This will depend on the amount of air "turn over," i.e., the ventilation of the area. For small confined spaces, one might wait a couple of days, whereas in a large area like a garage or airplane hanger, one might return to the area after a couple of hours. For more information about the specific solvent in the paint you are using, call the customer service and/or health departments of the manufacturer.

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The National Institute of Environmental Health Sciences (NIEHS), a component of the National Institutes of Health, supports research to understand the effects of the environment on human health. For more information on environmental health topics, please visit the Web site at www.niehs.nih.gov.

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