I found this in PHIUS Tech Corner, June, 2012; Spray Polyurethane Foam Insulation
Spray Polyurethane Foam Insulation and Passive House.
How SPF is made
In order to create SPF insulation in large quantities under high pressure, a chemical
reaction of the two component parts, commonly referred to as “Side A” and “Side B”, has to occur. In commercial SPF systems, the A and B sides are mixed in a 1:1 volumetric ratio . In large-scale applications, these two components are typically stored separately in 55 gallon drums.
Side A contains chemicals known as isocyanates. Side B primarily contains a polyol,
which reacts with isocyanates to make urethane. The most common isocyanate compound used in SPF is methylene diphenyl diisocyanates (MDI) .
Side B is a proprietary blend of chemicals in addition to the polyol that allow formulators to
tailor the performance properties of the final polyurethane. Other materials contained in Side B
normally include :
• Blowing agents
• Flame retardants
• Amine or metal catalysts
Since Side B is a proprietary blend of chemicals, the identity of some of these chemicals
is not known, nor are the proportions, except to the manufacturers and formulators. The best available information indicates that the flame retardant most commonly used in spray
polyurethane foam insulation is TCPP (Tris (1-chloro-2-propyl) phosphate) (1). TCPP is
combined with a reactive brominated compound to form a polymeric brominated flame retardant
. TDCPP (Tris (1,3-dichloro-2-propyl) phosphate) is also used as a flame retardant.
In small applications, when pressurized 16 oz. cans are used, the SPF components are
pre-mixed in controlled amounts along with a propellant. However, some “do-it-yourselfer”
supplies now come in the separate two part formulations, typically in 5lb, 10lb, 40lb, or greater, low pressure cylinders.
SPFs made with soy or other natural or bio-based ingredients
SPF is made primarily from petroleum derived chemicals. Some SPF may be advertised
as being “green”, “natural” or, “environmentally friendly”, due to having been partially made
from natural ingredients, such as soy bean oil, castor oil, and other bio-based oils, etc. However, these oils may only be a low percentage of the Side B mixture and still be advertised as green ornatural . Current technology limits the use of natural oil polyols to about 1/3 of the total polyols, as excessive use of natural oils can affect the dimensional stability of SPF .
Typically, the balance of the polyol used in Side B is still petroleum derived, as are the
isocyanates in Side A – 50% of the total mixture.
Recently, the U.S. Department of Agriculture (USDA) proposed new regulations
requiring at least 51% of the total product formulation be from natural ingredients in order for a product to be called bio-based . If finalized, this new regulation would prevent SPF from being labeled “bio-based”.
It then goes on to mention…
Human health/indoor air quality concerns with SPF
There can be health risks from exposure to isocyanates and some of the other ingredients,
used to manufacture SPF insulation , , . The primary health risks are from exposure
during the installation stage while the foam insulation is being sprayed , , . Health risks are of most concern for spray foam workers, and possibly other workers in the spraying area, especially if they are not properly protected , , .
However, homeowners or building occupants may also be at risk if certain precautions
are not taken , , . More recently, there have been reports from homeowners of incorrect installations of spray foam that have triggered health problems and indoor odor issues , .
Researchers and manufacturers are looking into these incidents as well as currently investigating any long-term health effects associated with the product .
Isocyanates, the primary ingredient in SPF, are well known inhalation and dermal
“sensitizers” that can trigger a severe or fatal asthma attack in some people who become
sensitized, even at very low levels . A sensitizing chemical is one that after multiple repeat exposures, may cause the human body to react in an abnormal or over-reactive way, even to extremely low doses, when initial exposures may not have had an impact. The more the body is exposed to the chemical the more it has a negative reaction to it. In some cases, certain individuals can quickly become sensitized to these types of chemicals such that there are no safe levels of exposure , .
Isocyanates are the leading attributable cause of work-place related asthma , . SPF
insulation also contains potentially hazardous amine catalysts, blowing agents, flame retardants and other constituents .
With the widespread and increasing use of SPF insulation, unnecessary exposure for SPF
applicators and other trade workers or other building occupants (e.g., homeowners, children, office workers, etc.) may occur if proper precautions are not taken during the spray applications and shortly after.
While applying SFP, aerosols and vapors are generated that can be inhaled or come in
contact with the eyes or skin. Potential sensitization may occur through exposures on the skin as well as through inhalation . Individuals, in particular installers of SPF as well as
homeowners, with a history of skin conditions, respiratory allergies, asthma, or prior isocyanate sensitization should carefully review product information when considering the use of SPF products and may want to consider other insulation alternatives. This especially applies to high pressure applications but also to low pressure applications. With low pressure applications,which mechanically mix the A and B side chemicals inside a nozzle, instead of impingement mixing of aerosolized chemicals in high-pressure foams, the amount of vapors and aerosols tends to be lower, but they are still generated during installation .
Manufacturers who have prepared complete and accurate SPF Material Safety Data
Sheets (MSDS) typically recommend in the MSDS that individuals undergo medical surveillance prior to working with these materials, and individuals with a history of medical conditions such as asthma, be restricted from working with isocyanates .
The following were noted in the 2006 National Institutes of Occupational Safety and
Health (NIOSH) Alert — Preventing Asthma and Death from MDI Exposure during Truck Bed Liner and Related Applications . NIOSH issued this, and a 1996 Alert, in follow up to worker deaths after exposure to isocyanate containing polyurethane automobile paint and exposure to isocyanates in polyurethane foam manufacturing. NIOSH concluded that the
potential for exposure to isocyanates from spraying polyurethane foam insulation is very similar to these prior incidents .
• “Isocyanates have been reported to be the leading attributable chemical cause of work-related asthma,.
• Exposure to isocyanates can cause contact dermatitis, skin and respiratory tract irritation, sensitization,
• Both skin and inhalation exposures can lead to respiratory responses.
• Isocyanates can cause “sensitization,” which means that some people may become allergic to isocyanates
and could experience allergic reactions including: itching and watery eyes, skin rashes, asthma, and
other breathing difficulties. Symptoms may also be delayed up to several hours after exposure. If you are allergic or become sensitized, even low concentrations of isocyanates can trigger a severe asthma attack or other lung effects, or a potentially fatal reaction.
• Some workers who become sensitized to isocyanates are subject to severe asthma attacks if they are exposed again. Death from severe asthma in some sensitized persons has been reported.
• Sensitization may result from either a single exposure to a relatively high concentration or repeated exposures to lower concentrations over time.
• Even if you do not become sensitized to isocyanates, they may still irritate your skin and lungs, and many years of exposure can lead to permanent lung damage and respiratory problems.
• All skin contact should be avoided since contact with skin may lead to respiratory sensitization or cause other allergic reactions.
• Appropriate Personal Protective Equipment (PPE) should be used during all activities that may present exposure to any isocyanate compounds to avoid sensitization.”
As mentioned above, Side B contains a blend of proprietary chemicals that provide unique
properties to the foam, and may vary from manufacturer to manufacturer. Given this, it is
difficult to precisely identify all potential health effects of the Side B components, but the
following is reported .
• Catalysts may be amine or metal catalysts. Amine catalysts in SPF can be sensitizers and irritants that can cause blurry vision (halo-effect) , .
• Flame retardants, such as halogenated compounds, can be persistent, bioaccumulative, and/or toxic chemicals (PBTs). Some examples include:
TCPP -(Tris (1-chloro-2-propyl) phosphate) TEP -(Triethyl phosphate)
TDCPP (Tris (1,3-dichloro-2-propyl) phosphate)
• Blowing agents may have adverse health effects, as well as be green house gases.
• Some surfactants may be linked to endocrine disruption .
Recently, the State of California released a study indicating that TDCPP has a carcinogenic
effect in laboratory test rats .
Potential for exposure to these chemicals
Exposures to SPF chemicals may occur through a variety of ways depending on whether it
is the SPF applicator(s) and other workers, or the owner or resident of a building that is being SPF insulated. When SPF installation is ongoing, the work site should be restricted to only trained persons wearing appropriate Personal Protective Equipment (PPE) , , . NIOSH (and the industry represented by CPI and SPFA) recommend that PPE for SPF workers include , :
• Full-face supplied-air respirator (with a pump/filter/hose supplying fresh air).
• Face mask, with a peel-off shield for clear visibility as foam aerosols will coat the mask
after a duration of spraying.
• Full body suit and chemical-resistant gloves and boots.
• All exposed skin must be fully covered.
• A ventilation system to ventilate the work area, during and after spraying.
• NIOSH also recommends a containment structure or enclosure for the area where
spraying is occurring.
During spraying, vapors and aerosols of isocyanates and the other components are
generated. Research data indicate that inhalation exposures without PPE to isocyanates during
SPF installation will typically exceed OSHA occupational exposure limits (OELs) . In
addition, vapors and aerosols can migrate through a building if the spray area is not isolated and properly ventilated. After application, vapors may linger in a building until properly ventilated.
This supports current practice to vacate the premises during installation and for a specified
period of time following installation.
Cutting or trimming the foam after it hardens may generate dust and particles that contain
unreacted isocyanates and other chemicals . After application, foam dust may linger in a
building until properly ventilated and thoroughly vacuumed.
Unprotected (without PPE) homeowners or residents should not be present when a high
pressure foam application is ongoing in the house. A homeowner or resident could also be
exposed to isocyanates and the other chemicals if they re-enter the structure too soon after application , , .
Another important factor relating to the potential exposure to isocyanates and the other
components is the time it takes for the SPF to cure. Curing of SPF means that the chemicals in the product are reacting to produce polyurethane foam. 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 and may still be off-gassing these
Some estimates indicate that it can take approximately 24-72 hours after application for
the foam to fully cure for the two-component high pressure “professional” SPF systems, and approximately 8 to 24 hours to cure for one component foam available in the small cans, but more research is needed to account for the potential variability of curing rates. , , 
The curing time may vary depending on the type of SPF product (open or closed cell),
product formulation, applicator technique, foam thickness, temperature, humidity and other factors, which will impact re-occupancy time. Temperature and humidity play a critical roll in the curing of SPF ingredients as does proper installation (applicator training, technique and maintenance and quality of the equipment that is used). More research is needed to understand the role these variables play in future potential off-gassing.
A homeowner who is erroneously advised they can stay in a house without PPE while the
SPF is being installed, can be exposed to unhealthful levels of the spray foam chemicals. Or, if they return to the house too soon after spraying, may also be exposed to high levels. Likewise, ifsomething went wrong during the installation and the foam has yet to cure, or never does fully cure, then exposures can also occur when the home is re-occupied.
The US EPA states, if home or building occupants have concerns that they may be
exposed to residual SPF chemicals, potential off-gassing, or continue to smell odors, they should contact their SPF contractor to ensure proper procedures and clean-up were followed . If their concerns are not resolved, affected parties should contact their local or state consumer protection office or contractors’ licensing board. Consumers can also file an online Consumer Product Incident Report with the U.S. Consumer Product Safety Commission on the SaferProducts.govwebsite .
Additional pathways of exposure to SPF chemicals for homeowners and residents, as
well as workers, after the foam insulation is installed may include heat-generating processes such as drilling, welding, soldering, grinding, sawing, or sanding on or near SPF insulation . This may generate a range of airborne degradation chemicals including isocyanates, amines, carbon dioxide, carbon monoxide, hydrogen cyanide, or nitrogen oxides . These potential releases raise possible concerns for future renovations, alterations and even demolition.
Fires involving SPF may release isocyanates, hydrogen cyanide, amines, and other highly
toxic chemicals into the air. Fire departments have issued advisories and require the use of full supplied air respirators for firefighters when fighting fires with burning polyurethane foam insulation.
Reported problems with the use of SPF
Since 2009, homeowners or others have been reporting spray polyurethane foam
insulation problems to the Consumer Product Safety Commission (CPSC) . A review of the
reporting at the time this article was written, reveals there have been at least six cases reported to CPSC where homeowners have become sick after installation of SPF insulation in their homes
A recent paper in the Journal of Occupational and Environmental Medicine reported the
first documented case of SPF isocyanate-induced asthma in two otherwise healthy homeowners
who were allowed to return to their home too soon after the attic was spray foamed .
There are also numerous other reports of spray foam off-gassing causing health problems
on consumer-sponsored spray foam websites and in green building blogs , , . Health
effects such as headaches, chest pains, eye, and throat irritation, rashes and coughs and asthmalike
symptoms are reported.
Lingering, irritating odors that smell sweet, fishy with a chemical-like or ammonia-like
aroma that won’t dissipate, even with extended ventilation, have been complaints in a number of these cases. The SPF industry attributes lingering odors to the amine catalysts .
In some cases, homeowners or residents who reported having no respiratory problems or
symptoms prior to the foam installation, reported they began experiencing burning throats,
irritated eyes, difficulty breathing and other various symptoms immediately after, or within a day or two after, foam installation when they re-entered their house. In some cases, the homeowners or residents indicated they experienced a relief of the symptoms after they spent time away from their homes. Some homeowners reported having to move out of their homes because of the
concern for their health. In a growing number of cases, homeowners report having the spray
foam insulation completely removed from their homes in an attempt to remediate the situation
and to be able to return to their house , .
The cause of these incidents is unclear. Although more evidence needs to be gathered to
determine patterns and commonalities between the cases, the most likely cause of problems with
the SPF insulation is an incorrect installation since industry representatives have data to show
that when SPF insulation is properly formed and it has fully cured, there is no residual offgassing
of any of the chemical components. In some instances of improper installation, the SPF
manufacturer has, or is initiating, the removal of installed SPF insulation as a way to remediate
the odors and health concerns of homeowners.
As discussed above, numerous variables can affect whether high pressure SPF insulation
installation is done correctly, and most of these variables are controlled by the SPF installation
contractors on-site at the time of application.
It is important to note installing SPF insulation in a house or building is an on-site
chemical manufacturing process in a location that will be occupied shortly thereafter (by workers or owners), and continuously for years on end. If anything goes wrong during the process the effects are experienced on-site, rather than at a factory as with other insulations. There has been discussion on a green building website that with an incorrect SPF installation, the chemical ingredients of the foam can even be absorbed by the building materials with which it comes into contact .
The most likely variable that is leading to these incidents is human error. Human errors
in knowledge and performance, which can lead to incorrect mixtures of the chemical
components, incorrect temperatures and pressures during the spraying, poorly maintained spray equipment, equipment, or spraying when ambient temperatures or building substrates are too cold, or humidity is too high for a proper chemical reaction and proper curing. One error that has been reported is applying too thick of a layer of SPF in one pass. The proper procedure for applying closed cell foam insulation is to spray 2 inch (maximum thickness) layers, allow time to cure, and then applying additional 2 inch (maximum thickness) layers if more insulation has been specified. In one reported case an entire 6-8 inch layer of closed cell foam was applied at once by the applicator who did not follow the recommended application procedures provided by the SPF manufacturer.
In addition, there have been reports of house fires spontaneously starting after the
installation of SPF due to excessive heat build-up from the exothermic reaction of the foam.
To view this article in its entirety see PHIUS_Spray_Polyurethane_Passive_Houses-2