By Harry Dietz, Director of Risk Management, NRCA
Spray polyurethane foam (SPF) is a roof system installation with unique chemical components, application techniques, and worker protection requirements that vary from other roof system installations. Although edge, skylight, ladder, and roof opening hazards are also found in SPF installations, a roofing contractor faces unique challenges when implementing controls to minimize other SPF hazards because of the unconventional nature of SPF materials and processes. This article focuses on some of the hazards related to an SPF roof system installation and the personal protective equipment (PPE) that may be useful and/or required to minimize or eliminate worker exposures and maintain compliance with Occupational Safety and Health Administration (OSHA) rules.
Airless spray equipment is used by an applicator to apply a two-component mixture that forms the base of an SPF roof system. Component A of the mixture ordinarily is methylene diphenyl diisocyanate (MDI) or a similar isocyanate-based compound when combined with the B-side of the mixture, a polyol resin, forms a liquid that expands and cures to a closed-
Isocyanates are a group of chemicals used in the manufacture of polyurethane plastics, synthetic rubbers, foams, paints, varnishes, and adhesives. Polyol resin is a chemical used in the formulation of polyurethanes; in the case of an SPF roof system, a high-density polyurethane foam. Additional chemicals may be present in SPF for various functions. A protective surfacing, such as a coating, ordinarily is applied to the cured SPF with airless spray equipment or brush and roller.
Whenever any type of material is applied with airless spray equipment, the danger of inhalation of respirable particles of a chemical or contaminant is possible. Limiting worker exposure to gases, vapors, fumes, dusts, and mists is required under Subpart D of the OSHA construction regulations (29 CFR §1926.55). OSHA requires “feasible” engineering or administrative controls to first be used to minimize worker exposure and PPE used if controls are infeasible or insufficient to keep worker exposures below set limits. Monitoring personal breathing samples is the only sure method of determining a worker’s inhalation exposure. Manufacturer’s safety data sheets (SDSs) for SPF components provide specific information as to the hazardous chemicals present in the A- and B-sides that could pose a risk to workers, the permissible exposure limit (PEL) for each chemical and the recommended work practices and respiratory protection to minimize or eliminate the exposure. The hazard of most concern with the A-side or isocyanate component of SPF is respiratory sensitization. Certain individuals may become sensitized to isocyanates after repeated overexposures above the permissible exposure limit or, in rare cases, a significant one-time exposure. Subsequent exposure of those individuals to even minor concentrations of isocyanates can result in symptoms such as wheezing, shortness of breath, coughing, chest tightness, and in some cases asthma attacks. According to the American Chemistry Council Center for the Polyurethanes Industry (ACC CPI), asthma attacks in such instances may be life-threatening; so manufacturers recommend sensitized individuals avoid subsequent respiratory or even skin contact with isocyanates at any concentration level.
A review of several SDSs for the isocyanate component of SPF indicates that respiratory protection is required at all times to avoid possible symptoms. Control methods for respiratory hazards described in SDSs include a minimum air-purifying respirator with dust filter and organic vapor cartridge. It is critical that filter and cartridge replacement schedules are set and adhered to so that respirator function is maintained. Supplied air respirators using breathing air from an uncontaminated source are recommended in some SDSs when MDI levels exceed those at which an air-purifying respirator may be effective.
Some coatings applied to SPF roof systems present similar inhalation hazards particularly when applied with airless spray equipment. Those hazards may involve both solvent-based and acrylic or waterborne SPF coatings. A review of the SDSs of a variety of coatings indicates that respiratory protection is universally recommended by manufacturers for all spray application of coatings. At a minimum, half-mask or full-face air-purifying respirators with dust filters and organic vapor cartridges are required.
Another hazard that is often overlooked when using airless spray equipment involves material being injected into the skin from contact with pressurized fluids. System pressure produced by SPF spray equipment can exceed 2,000 pounds per square inch and airless sprayers for coatings also operate at high pressures. Failure of hoses or couplings has the potential to release liquids at significant pressure sufficient to inject material under the skin. Contact with a spray gun tip may also cause an injection injury. ACC CPI has the following recommendations:
- Before use, check hoses for cuts and damage.
- Tighten all connections securely.
- Do not attempt to repair a hose with tape.
- Do not treat a wound from pressurized fluid as merely a cut—get emergency medical attention immediately.
Other PPE that is critical to minimize exposure during SPF operations include a spray sock or hood for head protection, goggles, or full facepiece for eye and face protection, chemical resistant gloves made with butyl, nitrile, or chloroprene rubber or polyvinylchloride and a full-body protective coverall.
As with all hazardous chemicals workers encounter on the job, SDSs for SPF products must be readily accessible during workers’ shifts so that critical information is available to avoid injuries or complications from exposure. Maintenance of SDSs is just one component of an OSHA-mandated written hazard communication program.
Harry Dietz is the Director of Risk Management for the National Roofing Contractor’s Association (NRCA). At NRCA, Harry’s responsibilities include staff liaison to the Health and Safety Committee, updating and developing content for NRCA’s Safety Manual and other safety products. He is a member of the American Society of Safety Engineers, American National Standards Institute’s A-10 Construction Standards Committee, ASTM Skylight Human Impact Workgroup, and ISO 45001 Technical Advisory Group. Harry is an authorized trainer for the 10- and 30-hour OSHA construction safety classes and also teaches NRCA’s fall protection class, and CERTA torching safety and form training classes.