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HHI-Pedia Entry

Polyurethane and polyisocyanurate

By HHI Staff

The basic ingredients of polyurethane foam are isocyanates, polyol resins, and an amine catalyst. Other additives can be used. A blowing agent causes the mixture to expand, creating a foam. Polyurethane can be made into flexible foam, as used in upholstery, or a rigid foam, as used in insulation, depending on the type of isocyanate used.


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Reported health effects in factories that produce polyurethane include: blurred vision, skin, eye and respiratory tract irritation, asthma, chest discomfort, etc. Some of the chemicals causing these symptoms outgas rather quickly, but others do not. Isocyanates are sensitizers. This means that they can sensitize a person and, once sensitized, that person will react to lower levels. Once these foams are cured, they no longer act as sensitizers.


Polyurethane is flammable and must be separated from the living space by drywall or plaster. It burns rapidly and releases carbon monoxide, oxides of nitrogen, and hydrogen cyanide. Hydrogen cyanide is lethal (it’s used in gas chambers) but so much carbon monoxide is released in a fire that it’s of more concern. A group of firemen, who were exposed to isocyanates, reported numerous neurological symptoms such as: euphoria, headache, difficulty concentrating, poor memory, and confusion.

Fire Hazard

"Based on valid scientific evidence, polyurethane foam and comparably combustible fillings used in upholstered furniture and mattresses are too dangerous for use in the home, unless they are treated to resist fire or are safely encapsulated. Manufacturers who choose to use these highly combustible materials inappropriately do so with the knowledge that they are placing their customers at risk of death and serious injury. Accordingly, NASFM urges the use of only fire-resistant or safely encapsulated fillings for the manufacture of upholstered furniture and mattresses."


National Association of State Fire Marshals (NASFM)

Polyurethane insulation has a higher R-value than some other insulations because of the blowing agent trapped in its pores. Other insulations use trapped air to retard the flow of heat, but the gas used in polyurethane functions as a better insulator. However, as the material ages, the gas slowly escapes and is replaced with air. This results in a lower R-value as the insulation gets older. The escape of gas can be largely prevented by coating the polyurethane with a dense skin, or a layer of metal foil. Polyurethane used, for example, inside a sealed steel entrance door, would probably allow little gas to escape.


Polyurethane will degrade and fall apart in sunlight unless ultraviolet inhibitors are used in the formulation. It will also take on water when in a damp environment or used underground, so it must be adequately protected with a suitable diffusion retarder.


Polyisocyanurate foam insulation is very similar to polyurethane, but is slightly more stable. It, too, must be protected from sunlight and moisture and it has similar characteristics when burned. It is often supplied with a foil facing to protect it from degradation.


While workers in manufacturing plants can be exposed to a variety of chemicals, polyurethane and polyisocyanurate insulations are fairly inert once cured.


(Note: The views expressed in this article are those of the author, and do not necessarily represent those of The Healthy House Institute, LLC.)


From The Healthy House, 4th edition, by John Bower, published by The Healthy House Institute (HHI).


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Polyurethane and polyisocyanurate:  Created on June 4th, 2009.  Last Modified on February 28th, 2011


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