Construction Risk Insights: Spray Polyurethane Foam Hazards

By | October 23, 2013

Construction Risk InsightsSpray polyurethane foam (SPF) is an effective insulation and air sealant material. However, workers in the SPF industry can be exposed to inhalation hazards from isocyanates and other hazardous chemical vapors or dusts. OSHA requires a hierarchy of controls, under which employers must first implement engineering controls (including elimination and substitution) and/or administrative controls whenever possible.

The use of SPF in retrofitting older buildings to conserve energy has increased over the past few years, but exposures to its key ingredient, isocyanates such as “MDI,” and other SPF chemicals that may be found in vapors, aerosols or dust, or on surfaces during and for a period of time after installation, may cause adverse health effects such as asthma, lung damage, other respiratory problems and skin and eye irritation. As an employer, safety when working with SPF should be a top priority while on the jobsite.

Chemicals in SPF

In order to create the final SPF insulation or sealant product, a chemical reaction of the two component parts, commonly referred to as Side A and Side B, has to occur. SPF products contain approximately 50 percent Side A and 50 percent Side B. This chemical reaction generates heat.

Side A contains very reactive chemicals known as isocyanates. Side B contains a polyol (which reacts with isocyanates to make polyurethane) and a mixture of other chemicals, including catalysts (which help the reaction to occur), flame retardants, blowing agents and surfactants.

There is concern for exposure to any isocyanate-containing material related to SPF use, including products that contain only a single isocyanate. It is important to know what other products contain isocyanates because if workers become sensitized to isocyanates, even low concentrations of isocyanates can trigger a severe asthma attack or other lung effects, or a potentially fatal reaction.

Types of SPF Products

There are three main types of SPF products, each of which have different application uses. All SPF products require the use of protective equipment in order to prevent exposure to isocyanates and other SPF chemicals.

  1. Two-component high-pressure SPF is often used for larger projects such as roofs and attics. It usually comes in large drum containers and is either open-cell (low density, expands aggressively, dries soft, lower R-value) or closed-cell (high density, expands less aggressively, dries rigid, higher R-value).
  2. Two-component low-pressure SPF is often used in smaller applications as an air sealant or adhesive or for weatherization. Unlike two-component high-pressure SPF, this type can be well-suited for do-it-yourselfers in addition to professional contractors. This type often comes in small containers (3-5 gallons) and the two chemicals must be combined at the jobsite before application.
  3. One-component foam is often used as a sealant when filling in cracks around windows and doors and is suited for do-it-yourselfers as well as professionals. This type comes in small cans in which the chemicals are already mixed together, ready for spray-on application.

Engineering Controls for SPF Application

OSHA requires a hierarchy of controls, under which employers must first implement engineering controls where feasible.

Ventilation and containment practices should be considered to control chemical exposures when applying SPF. Areas where SPF is being sprayed should be separated from other portions of the building. In addition, ductwork should be sealed to prevent the spread of fumes or vapors to other areas. Air handlers (fans) should move air across the room in one direction and move vapors/air contaminants away from the operator and other workers in the area.

Work in “permit-required confined spaces” requires entry procedures, including an entry permit and training for the workers. For construction or reconstruction work attics, crawl spaces and overhangs with limited ceiling space or small space can be considered a confined space, especially for the purpose of SPF application.

The Right PPE for the Job

When the use of engineering controls is not feasible or adequate to control exposures, personal protective equipment (PPE) must be used. Generally, it is good practice to use PPE regardless of the engineering control in place.

Whenever employees are working with SPF, the following PPE should be supplied:

  • Eye protection, including safety goggles or face shields
  • Hand protection, including chemical-resistant gloves made from chloroprene rubber (Neoprene), butyl or PVC
  • Body protection, including saran-coated material, such as a full body suit with an applicator hood
  • Employees should always wear tops with long sleeves.
  • One of three types of respirators:
  1. Air-purifying Respirators (APRs), which use filters, cartridges or canisters to remove contaminants from the air the user breathes.
  2. Powered Air-purifying Respirators (PAPRs), which have a blower that pulls air through attached filters. The blower then pushes the filtered air into the facepiece, which covers all of the user’s face. Since it is loose-fitting, it does not need to be fit tested and can be used by workers with facial hair.
  3. Supplied-air Respirators (SARs), which supply the user with breathing air from a source independent of the ambient atmosphere.

The type of SPF application will determine which respirator is most effective for the job. When applying two-component high-pressure SPF, SARs are recommended. APRs and PAPRs are suitable for two-component low-pressure SPF and one-component foam. Always remember to check the respirator’s filter before use and replace if needed.

Curing and Re-entry Hazards

“Curing” of SPF means that the chemicals in the product are reacting to produce polyurethane foam. SPF material is highly adhesive and will stick to most surfaces. SPF may appear hardened or “tack-free” within a range of a few seconds to a few minutes after application. However, at this stage, the foam is still curing and still contains unreacted SPF chemicals.

Some manufacturers estimate that it can take approximately 23-72 hours after application for the foam to fully cure for the two-component high-pressure SPF and approximately eight to 24 hours to cure for one- component foam.

Ultimately, the curing time (complete reaction) varies depending on the type of SPF product, product formulation, applicator technique, foam thickness, temperature, humidity and other factors, which will impact re-occupancy time. It is important to be in contact with the building’s owner or decision-maker to discuss re-entry procedures.

Air sampling and testing the indoor air following SPF installation is one way to ensure the foam is completely cured. Emissions testing of SPF foam applied in a laboratory and in the field (at the worksite) may vary. Testing should be conducted by a certified laboratory using a validated method.

After SPF is applied and cured, it is considered to be relatively inert; however, there are several situations where the cured foam may pose additional potential risks:

  • Maintenance workers, including plumbers and electricians, should not heat or grind spray foam. Spray foam can potentially generate toxic emissions under these circumstances.
  • Building renovations, demolition or building disassembly done years later can disturb spray foam insulation. Performing hot work on or near SPF may lead to potential exposures to isocyanates and other toxic emissions.

Best Practices Throughout Entire SPF Application Process

Training and Comprehension

  • Make sure employees are properly trained to apply SPF.
  • Read the SPF manufacturer’s Safety Data Sheet and follow directions to achieve consistent curing conditions and times.
  • Be prepared to carefully manage temperature and other area conditions while the SPF dries or cures. Unpredictable or uncontrolled curing rates can increase the risks of exposure.
  • Make sure all applicators and helpers understand ahead of time how to safely handle chemicals, the dangers of exposure and factors that affect curing, and that they have the appropriate PPE on hand.
  • Understand how to discuss SPF application with building owners and occupants, including plans to vacate during and after installation.


  • Receive medical surveillance to ensure applicators and helpers are healthy enough to wear a respirator.
  • Vacate building occupants and other trade workers who are unprotected.

Application Process

  • Isolate the work site to prevent isocyanates and other chemical vapors from spreading to other rooms or floors.
  • Make sure workers wear the proper protective equipment at all times to avoid exposure to vapor, mist, particulates and dust.
  • Ventilate the work area.


  • Clean the work site thoroughly to avoid exposing other workers and building occupants to dust and particles that may contain isocyanates and other SPF chemicals.
  • Remove protective clothing and handle with care to avoid exposing yourself and others to toxic chemicals.


  • Clean before allowing other unprotected workers or building occupants back into the area.
  • Exercise caution when determining safe re-entry times.


Construction RI Spray Polyurethane Foam Hazards

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