Safety Is Key 

by Neeva-Gayle A. Candelori 

Posted: June 8, 2010 

When Applying SPF Roofing Systems 

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. 
Learn About SPF 

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 

For roofing systems, 

high-pressure, closedcell spray 

polyurethane foam is 

lightweight, durable, 

easy to apply, and 

can create a uniform 

seal over the 

substrate regardless 

of different shapes. 

However, proper 

application and safety

measures are critical.
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. 

Wear Proper Personal Protective Equipment

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 airpurifying respirator (PAPR) with organic vapor 

cartridges with particulate pre-filters or a suppliedair 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/secgrevcurrent.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 

The manufacturer’s 

Material Safety Data 

Sheets should be 

consulted prior to 

applying coatings for 

information on 

potential health 

hazards and PPE 

recommendations. 

OSHA requires that all

MSDSs be readily 

available to all 

workers at the 

jobsite.
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. 

Neeva-Gayle A. Candelori 

Neeva-Gayle A. Candelori is the Director of the Center for the Polyurethanes Industry of 

the American Chemistry Council. She holds a B.A. degree in economics from the 

University of Maryland. Bringing over 15 years of plastics industry experience to this 

role, she worked for leading chemical and plastic industry trade associations. Prior to 

joining the American Chemistry Council, she held positions at The Society of the Plastics 

Industry and The American Plastics Council. Her prior roles involved managing industry 

issues for the vinyl, color and additives and the healthcare sectors. She also serves as 

international advisory to the board of the Korean Polyurethane Society.