Sprayed Polyurethane Foams: An Explosive Issue

James Vallette | April 27, 2010 | Materials

This blog post, originally shared in the Pharos Signal, includes information about parts of Pharos that are no longer available. Please use it for historical reference and for the other useful information it contains.

"On a Saturday afternoon this past May, while pumping a two-part 'GREEN' soy-based foam into the attic ceiling of a Cape Cod home renovation, a fireball erupted, taking the hose man's life."

So begins a harrowing account by health and safety consultant Richard Hughes, in which he explores how a polyurethane spray foam applicator in Falmouth, Massachusetts, died on the job last year.

Sprayed polyurethane foams (SPF), especially those that contain soy-based polyols, are commonly called "green" building materials. Some people like its ability to tightly seal hard-to-access areas; others recite industry literature that trumpets the use of bio-based ingredients (soy) in the chemistry and the absence of free formaldehyde in the product.

There are multiple variations on ingredients used in SPF, but the key ones are the same. These are two part systems. One part is an isocyanate. The other part is a mix of polyols, flame-retardants, blowing agents, and other additives. Foam insulation installers follow the same basic steps that occur in industrial polyurethane factories, but in a far more confined space, combining Parts A and B in peoples' attics.

Before the foams arrive on the job site, there are upstream hazardous associations, including reactions with formaldehyde and chlorine. Like PVC, polyurethane uses significant quantities of chlorinated compounds in its manufacture leading to emissions of dioxins and furans. These persistent, bioaccumulative toxicants are highly potent carcinogens and endocrine disruptors.

The production of methylene diphenyl diisocyanate (MDI), the most prevalent isocyanate used in SPF, requires a whole host of chemicals at various stages, including toluene, benzene, nitrobenzene, aniline, formaldehyde, methylene dianiline (MDA), and phosgene (produced from carbon monoxide and chlorine).

SPF installers combine the isocyanate (Part A) with a mixture of polyols, additives and catalysts (Part B).

Polyols are made from adipic acid, variously with ethylene glycol, propylene oxide or other chemicals. Sometimes the polyols are produced with soy, but this accounts for less than 10 percent of the final polyurethane product.

Additives include surfactants, blowing agents, and flame-retardants, some of which are known to contribute significantly to global warming and ozone depletion. (See box below for examples). Catalysts, which trigger the two-part reaction, can include problematic heavy metals. A common catalyst is lead naphthenate.


Federal agencies are starting to look much more closely at SPF. OSHA, the Consumer Products Safety Council, U.S. Environmental Protection Agency, and National Institute for Occupational Safety and Health (NIOSH), have formed a Federal SPF Workgroup. The group aims to:


  • "Improve availability of accurate and comprehensive hazard and risk information." At a December 2009 Federal SPF Workgroup webinar, EPA official Mary Cushmac warned that do-it-yourself applicators are using two-component kits and "are often unaware of the hazards and the need to prevent skin, eye and inhalation exposures." She raised a question that, disturbingly, remains unanswered: "When can occupants, residents, and school children safely re-enter the premises after SPF application?" The agencies said fundamental guidance is needed for "ventilation, exposure controls, clean-up, and re-entry time."
  • "Address inaccurate or misleading marketing claims." The federal workgroup listed such claims as "No off-gassing", "non-toxic", "safe", "green", "environmentally friendly," "is plant-based", and "made from soy beans." A slide warns that the Federal Trade Commission "prohibits deceptive representation in advertising, labeling... and sales presentations."
  • "Address exposure assessment and data gaps." Janet Carter, an OSHA scientist, noted, "Only a few Material Safety Data Sheets mention the possible need for respiratory protection for 'adjacent workers'... and do not mention the possible presence of MDI."


"Worker exposures (are) not always considered in developing 'green' products and practices," charged NIOSH scientist, Dr. Daniel Almaguer. "A truly comprehensive approach to sustainability and green practices needs to include occupational safety and health aspects."

Drawing a lesson from the explosion on Cape Cod, Richard Hughes concludes, "Chemicals in the residential construction world are a far larger source for concern than we are presently acknowledging in manufacturers, distributors and our own independent safety literature."

Even less understood than occupational hazards are long-term user exposures from chemicals released into the household from the spray application process, and from the installed foam.

The Pharos Project database now evaluates several SPF insulation products. We are adding more each week. Please sign up to take a comprehensive look at the volatile chemical mixtures that insulation applicators handle as they manufacture polyurethane, attic by attic.