From rain and hail to sunlight and temperature extremes, a strong roof must endure a variety of conditions and last a long time. For roofing systems, high-pressure, closed-cell spray polyurethane foam (SPF) has become a popular choice due to its durability, and if installed properly, its ability to create a surface that resists permeation by water. SPF also is lightweight, easy to apply, and can create a uniform seal over the substrate regardless of different shapes and protrusions. Add to that its excellent performance as an insulation material and it’s easy to see why the long-term benefits of SPF are becoming more and more attractive to building owners.
The foam is created on the jobsite out of two liquid components. The components react together to create foam. As you’ll learn in this article, because the liquid components contain certain kinds of chemicals, handling the components safely and wearing appropriate personal protective equipment are important. Always read all information contained in your supplier’s Material Safety Data Sheet (MSDS), and follow the safe handling guidelines provided.
There are several “kinds” of spray foam that a contractor might encounter at a site. Although the term “spray polyurethane foam” can apply to several different kinds of products, in this article we address high-pressure, closed cell foam.
The foam itself is made by mixing batches of chemicals that are provided in separate drums. The chemicals must be kept separate until they are mixed and the chemical reaction can begin. The two separate drums or canisters have different chemicals in them, and are referred to as the “A” side and “B” side. The A-side is typically a 50/50 mixture of methylene diphenyl diisocyanate (MDI) and polymeric methylene diphenyl diisocyanate (pMDI), or MDI-based diisocyanate. The B-side is a polyol resin blend - the principal ingredient being polyol - and smaller amounts of amine and/or metal catalyst, blowing agent, surfactant and flame retardant. The drums may be color-coded red or black for the A-side, and blue or another color for the B-side.
The degree of hazard (risk) presented from the chemical in the mix varies. There is a difference, for example, in the amount of MDI available prior to mixing the chemicals; after they are mixed and begin reacting; and again after the reaction has been fully completed and the foam hardens. Extreme care must be taken when working with the SPF pre-mix chemicals and throughout every stage of the installation. Improper application by unprotected workers could result in overexposure to the SPF chemicals, which can pose potential health hazards.
Understand Potential Health Hazards
Potential health hazards of SPF chemicals are discussed in the MSDS for the particular product, and workers should read and understand the MSDS before beginning work on a job. While we cannot review all the potential health effects that could result from spray foam chemicals here - and this specific information would be contained in the product MSDS - you should understand that a worker could be exposed to SPF chemicals by breathing chemical mists or vapors, skin or eye contact, or ingestion. One of the key things to remember with spray foam chemicals is that the A-side constituent, MDI, is considered a sensitizer. Inhalation exposure to MDI may lead to respiratory sensitization. Respiratory sensitization can lead to an asthmatic attack. Asthma attacks can be life-threatening events.
In addition, skin sensitization may occur as a result of skin contact with MDI. In animals, skin contact with MDI has led to respiratory sensitization.
To prevent inhalation of the SPF chemicals and contact with skin or eyes, personal protective equipment, or PPE, should be worn by all sprayers and helpers assisting them. Generally, for exterior applications like roofing, the following PPE is considered appropriate:
• A NIOSH-approved respirator appropriate for the anticipated workplace exposures. This may include an air purifying respirator (APR) or powered air-purifying respirator (PAPR) with organic vapor cartridges with particulate pre-filters or a supplied-air respirator (SAR).
• Disposable coveralls covering all exposed skin.
• Protective footwear, such as work boots.
• Nitrile, neoprene, butyl or PVC gloves.
Even when not spraying, PPE may be needed to prevent skin and eye contact during product handling in case splashes occur. Also note that the U.S. Occupational Safety & Health Administration (OSHA) requires employers to have a written Respiratory Protection Program (RPP) in place. OSHA makes available a Small Entity Compliance Guide that contains criteria for the selection of a Respiratory Protection Program administrator and a sample program that meets OSHA requirements. It is available at: www.osha.gov/Publications/SECG_RPS/secgrev-current.pdf.
Plan Ahead For a Safe, High-Quality Installation
Site preparation: An important initial step before any installation is to analyze the site. Just as an important feature of any job is to keep workers protected, the job plan should also take into consideration the safety of bystanders. Carefully evaluate whether bystanders could be exposed to drifting spray foam chemicals and address this in your site plan. Don’t forget that spray foam is an exterior application and can drift into homes and buildings, potentially impacting residents, so identify the location of air intake or exchange systems during the site analysis. It is a good practice to turn off the heating, ventilating and air conditioning system and all air handling units until the SPF has been sprayed and fully cured. In dense population areas, consider contacting nearby residents to assist them with similar measures, if needed.
Developing an Overspray Mitigation Plan can help determine in advance what actions will be taken in case of overspray. One feature of such a plan can be the advance identification and training of a point person(s) on the crew on procedures to address spill clean-up and overspray issues. The higher the wind, the more spray can drift, so ideal conditions for an outdoor SPF application have little to no wind. Depending on site conditions (e.g., population density, (subdivision or rural warehouse); nearby pedestrians; wind pattern and flow), it can be a good practice to postpone outdoor spraying in higher winds, such as sustained or gusty winds exceeding 15 miles per hour. Windscreens can also be an effective tool to help minimize overspray or spray drift. Follow the SPF manufacturer’s instructions carefully, including instructions on application during specific conditions of temperature and/or humidity.
Discussion of the installation with the building owner: One of the most important elements of your preparation is to plan a discussion with the building owner or homeowner. Discuss any potential overspray or spray drift issues with the building owner or occupants as part of your site preparation. Implement steps as appropriate. Consider asking building occupants to move, address building ventilation issues, and use tape or signs to mark both the work and potential spray drift area. Also consider pedestrian footpaths or bike paths, dog runs, or dog pens. After you have minimized potential for human exposures, consider whether additional steps could help protect property from overspray - such as relocating parked vehicles.
To protect the exterior of the building, a common practice is to cover any part of the building exterior that is not going to be sprayed (much like a painter places a tarp over a floor to keep it protected from paint spatters).
During your discussions with the homeowner, take the time to answer questions about how far away the building occupants should be from the installation - or whether they should vacate the building during the installation and for an appropriate period after completion. Building owners and occupants can also provide helpful assistance to you as you prepare the site, since they typically know the uses of their own property and air intake system well. SPF product suppliers can help provide you with specific guidance on questions regarding occupancy during the installation and reoccupancy times.
SPF application: Where feasible, plan the exterior application so that workers and helpers are upwind during SPF application. Only workers wearing appropriate PPE should be allowed in the spray area.
Remember to consult the manufacturer’s Material Safety Data Sheet (MSDS) prior to applying coatings for information on potential health hazards and PPE recommendations. Also, it is important to know that OSHA requires that all MSDSs be readily available to all workers at the jobsite. Because these documents are important, a good workplace practice is to keep a clean copy of each MSDS in a clearly marked binder at the jobsite and to review the content and location of the MSDS binder with all workers before the job begins. MSDSs and other health and safety literature can be obtained by contacting your supplier.
As with any job, housekeeping and cleanup after the job is completed are important. Conduct jobsite quality controls throughout the project and dispose of waste materials in accordance with any applicable regulatory requirements. Empty drums can be given to a qualified reconditioner or reclaimer for recycling. More information on drum reconditioning facilities can be found at www.reusablepackaging.org.
Spill response: It is advisable to have an emergency spill containment kit available that contains absorbent materials such as clay, pads, or socks to contain or minimize the affected area. If a spill does occur, direct personnel away from the immediate area and send those workers designated for spill cleanup to address the spill after they put on the appropriate PPE. The spilled material can be absorbed with sand, earth or absorbent clays and placed in drums. If MDI has been spilled, a neutralization solution can be used according to the MSDS. These drums should not be sealed for an appropriate period (e.g., at least 72 hours).
It is good practice to keep all chemical containers sealed except when they are actually in use. Although infrequent, sizable spills and releases of A- and B-side chemicals can occur. If this happens, it is important to take immediate action to minimize environmental contamination. You may be required to report spills and releases of SPF and coating ingredients to local, state, and/or federal authorities.
First aid: Refer to the MSDS for instructions in the event of inhalation overexposure or skin or eye contact with any chemicals over the course of your work. Any clothing contaminated with MDI should be removed and properly disposed of or decontaminated. Leather items cannot be decontaminated and will have to be properly disposed of.
Help Spread the SPF Safety Message
SPF has a great future as a key contributor to comfortable, energy efficient homes. Everyone wants a professionally installed - safely installed - SPF system that performs well over time. Help us spread the safety message. And for additional helpful guidance, see the Center for the Polyurethanes Industry’s website on spray foam, www.spraypolyurethane.com.