EPA—WORKING DRAFT—6/29/11 Page 1 www.epa.gov/dfe 

Overview of Key Principles

Establish air fl ow across the entire 

spraying area

Direct fans to establish the air fl ow 

Draw vapors, mists and dusts away from workers

Begin working at the exhaust end and progress 

downstream (away) from exhaust

Keep exhaust collection point as close to the 

source as possible

Establish enclosures to isolate and 

contain the work area

Place warning signs on entrances to the enclosure 

Maintain a negative pressure in the enclosure

Avoid openings that short circuit the ventilation

Seal off HVAC openings to prevent migration 

of contaminants

Direct exhaust to a safe location outside 

the building 

Direct exhaust away from workers or other 

people 

Direct exhaust away from air intakes for 

neighboring buildings

Establish control zones and post warning 

signs if needed

Filter exhaust air with particulate fi lters to protect nearby vehicles and other property 

Place the fi lter before the exhaust fan to ensure 

continued fan effi ciency

Continue ventilating the area after 

application

Check with the manufacturer to determine 

safe re-entry times

Minimize worker re-entry during this time

Ensure that those entering have proper 

protective equipment

Restrict occupant re-entry until after the building 

has been fully ventilated and cleaned

EPA’s Design for the Environment (DfE) Program

The DfE Program promotes safer chemicals and best practices that 

reduce exposures to chemicals of concern in the workplace and 

community. This Fact Sheet describes basic ventilation principles 

and strategies to help protect workers and building occupants and 

promote the safe use of spray polyurethane foam (SPF) insulation. 

What is Spray Polyurethane Foam (SPF)?

SPF is a widely used and highly-eff ective insulation and sealant material that is spray-applied to walls, ceilings, attics, basements, crawl 

spaces, and roofs. The two-component SPF systems (both high and 

low pressure) contain isocyanates (the A-side) and a polyol blend 

(the B-side). The A and B sides are fed through hoses to a spray gun 

where they are mixed and sprayed under pressure, rapidly reacting 

and expanding in volume to form polyurethane foam. 

Does SPF Application Present any Health Risks?

Yes, exposure to SPF chemicals poses health risks such as irritation 

and chronic lung disease to workers or others in the area if they are 

not adequately protected from skin, eye, and inhalation exposure. 

In addition, isocyanates (Aside) are strong sensitizers 

that can cause an allergylike response in certain 

people and are the leading 

chemical cause of work-related asthma. A person can 

become sensitized after 

long term or even initial 

exposure and a sensitized person can suff er a severe or fatal asthma 

attack if exposed even at very low levels. In addition, the polyol 

blend (B-side) contains blowing agents, amines, fl ame retardants, 

and other chemicals, which may also cause adverse health eff ects.

Why is Ventilation Important?

Properly designed ventilation can reduce airborne levels of aerosols, mists, and vapors generated during spray application and 

can help protect SPF applicators, helpers, and others who may be 

working in adjacent areas.

During and after spray application, vapors and mists, as well as 

particulates and dust from trimming or sanding the foam, may 

linger until the area is ventilated and fully cleaned. 

Construction activities should be carefully scheduled so that no other trades or occupants are in the building during SPF Installation.

Fundamentals of Ventilation

Ventilation is a method of controlling worker exposure to airborne 

hazardous chemicals or fl ammable vapors by exhausting contaminated air away from the work area and replacing it with clean air. 

There are two basic types of ventilation—general exhaust ventilation and local exhaust ventilation.

SPF spray application on wall

Ventilation Guidance

for Spray Polyurethane Foam Application
EPA—WORKING DRAFT—6/29/11 Page 2 www.epa.gov/dfe 

General exhaust ventilation systems typically consist of an 

exhaust fan, mounted in the ceiling or wall that pulls air out 

of the room and discharges it outdoors. Replacement air is 

brought into the area by either natural means, such as windows, doors, and exterior vents (e.g., attic vents) or could 

include a separate make-up air fan, duct work, and air registers 

that provide clean air to the room. General exhaust ventilation, also known as “dilution ventilation,” dilutes contaminated air by mixing it with cleaner room air. 

General exhaust systems are not recommended as the sole 

source of ventilation when hazardous vapors or mists are present, because they do not immediately remove contaminants 

from the work space. 

Local exhaust ventilation systems remove chemicals and other 

contaminants at their source. In these systems, the exhaust 

hood or vent is placed as close as possible to where the work 

is performed to capture and remove contaminants before they 

mix with the rest of the air in the room. Local exhaust ventilation 

systems are recommended for controlling hazardous vapors, 

mists, dusts, and particulates because, if designed properly, they 

remove the contaminants before workers are exposed.

For an SPF application project, a local exhaust system would 

be appropriate during the application process to capture 

vapors, mists, dusts, and particulates at the source as they are 

emitted during the spraying and trimming processes. General 

ventilation would be appropriate after the insulation is applied 

to ventilate the entire work area and building before other 

workers or occupants enter the area. 

SPF Ventilation Challenges

A ventilation system is normally designed to serve a specifi c 

location or room where the operation is well defi ned. For 

example, a spray booth used for spraying truck bed liners will 

always have the same room dimensions (i.e., volume and geometry) and the application process will always be the same. 

As a result, an eff ective ventilation system can be designed 

and installed to the exact specifi cations of the room.

The application of SPF to walls, ceilings, attics, and basements 

within multiple job sites, however, presents ventilation challenges because every job site will have diff erent room sizes 

and shapes. In addition, the process requires frequent movement of the workers as the work progresses resulting in vapors, mists, dusts, and particulates being generated throughout 

the room. This work area variability and movement prevents 

a “one size fi ts all” approach and presents challenges associated with designing a “booth-like” enclosure and ventilation 

system that can capture vapors, mists, dusts, and particulates 

at the source (i.e., the point of application). 

Because of this, it is important for SPF insulation applicators to 

understand some basic ventilation principles so they can implement eff ective ventilation controls in the wide variety of work 

confi gurations that they face. While a properly designed ventilation system can help protect workers and building occupants, an 

improperly designed system could make matters worse. 

Basic Ventilation Design Principles 

Because the source of emissions moves as the work progresses in SPF applications, designing a local exhaust system can 

be diffi cult. In fact, in many cases the system may look more 

like a general exhaust system. There are some tips to consider, 

however, to maximize the system’s eff ectiveness. The key to 

understanding and applying these tips is understanding the 

three important components of a ventilation system and how 

they work together. These components include:

■ The work space, room, or enclosure to be exhausted. 

■ The exhaust system—including a hood or exhaust vent, 

ductwork, and fan—that captures contaminants at the 

source and transports them to a location outside the 

building away from HVAC air intakes and occupied areas.

■ The make up air which is the fresh air to the room or work 

area that replaces the exhausted air. This can either be 

forced make up air (air forced into the room with a fan) 

or passive make-up air (air drawn into the room through 

openings such as doors, windows, or exterior vents).

How you design or place each of these components will determine the eff ectiveness of your system. 

Establish Air Flow Across the Spraying Area

A fundamental consideration of any ventilation system is that 

the system creates an air fl ow from the make-up air entry location to the exhaust collection point (e.g., hood or vent). It is 

important that this fl ow of air: 

■ Flows across the entire work space to be ventilated (see 

fi gure 1). This is achieved by ensuring the make-up air entry location is on the opposite end of the work area from 

the exhaust hood or vent.

■ Draws contaminants away from the workers. When possible, applicators should begin spraying near the exhaust 

hood or vent and progress away from that point so that off -

gassing from applied SPF is drawn away from the applicator. 

Helpers should also work upstream from the sprayer (see 

fi gure 1).

Ventilation Guidance

for Spray Polyurethane Foam Application

Protective Clothing and Equipment

The Occupational Safety and Health Administration (OSHA) 

requires that engineering controls such as ventilation and 

enclosures be used to reduce worker exposures to acceptable levels. When engineering controls alone are not suffi -

cient to reduce exposures to acceptable levels (typically the 

case for indoor applications of two component SPF systems), OSHA requires that workers wear appropriate protective equipment to prevent inhalation of and skin contact 

with contaminants. SPF manufacturer’s recommendations 

for proper respiratory and other protective equipment 

can be found in the product’s material safety data sheet 

(MSDS). Generally, these recommendations will include the 

use of full facepiece or hooded supplied air respirators. 
EPA—WORKING DRAFT—6/29/11 Page 3 www.epa.gov/dfe 

Related tips: 

■ Avoid improper placement and direction of fans. Simply 

pointing fans at the work area without establishing a 

directed air fl ow pattern will only stir up the air creating 

a greater potential for workers to breathe the contaminants. This could also lead to the unintended escape of 

contaminants to other work areas.

■ Remember to place the exhaust hood or vent as close to 

the point of application as possible. As an applicator moves 

around a working area, reposition the fans (so they remain 

close to the application process) if possible to account for 

a moving application point. Placing the exhaust fan close 

to the source of emissions minimizes the potential for the 

contaminants to mix with the rest of the air in the room. 

Establish Enclosures to Isolate and Contain 

the Work Area 

Establishing enclosures around the work area serves two 

important purposes:

■ Prevents migration of contaminants to other areas of the 

building. This protects workers in other areas and minimizes the need for more wide spread building ventilation 

during the application process and prior to occupancy.

■ Improves the effi ciency and eff ectiveness of the ventilation system by minimizing the size of the area to be 

ventilated (which aff ects the number and size of fans 

needed) and by helping to direct or channel the airfl ow to 

the exhaust vent or hood.

In some cases the confi guration and size of the room where 

the application will occur may be suffi cient to isolate the work 

area. In other cases, it may be necessary to construct temporary enclosures. Such enclosures typically include plastic sheeting with overlapped seams sealed with tape. 

Remember to place warning signs on entrances to the enclosure or work area to alert other workers of the hazard and 

prevent them from entering the area. 

Related tips:

■ Maintain a negative pressure in the work area or enclosure. This is accomplished by ensuring that you exhaust 

more air from the room than you supply. A negative pressure in the enclosure will prevent contaminated air from escaping the enclosure by ensuring that if there are any leaks, 

the leaks will be into rather than out of the enclosure. If 

you use forced supplied air, you can maintain a negative 

pressure by ensuring that your exhaust fan capacity (CFM) 

is greater than your make up air fan (a good rule of thumb 

is for your exhaust fan capacity to be 10 percent greater 

than your supply fan). If you use passive supplied air, your 

exhaust fan alone should be suffi cient to create a negative pressure. A smoke tube can be used as a basic tool to 

evaluate whether the enclosure is under negative pressure.

■ Avoid openings that will short circuit your ventilation 

system. Remember that because you have a negative 

pressure in your room or enclosure, air will be drawn into 

the room from any opening (intentional or unintentional). 

Poorly placed openings can short circuit your intended 

fl ow of air and create dead spaces (see fi gure 2). This is 

particularly important with passive make up air systems.

■ Remember to shut down and seal off HVAC openings in 

the work area to prevent migration of contaminants to 

other areas of the building, as noted earlier. Don’t forget 

to unseal and restart the HVAC system prior to re-occupancy after the SPF has fully cured and the work area has 

been ventilated and cleaned.

Direct Exhaust to a Safe Location 

Always remember to direct exhaust to a safe location outside 

the building, away from areas where other workers or people 

are or could be present. If the exhaust is at ground level or at 

other areas where people could enter, you should also establish a control zone using warning signs and physical barriers 

around the exhaust area to prevent personnel access. You 

should also be aware of where air intakes are for neighboring 

buildings and direct your exhaust away from these areas.

Ventilation Guidance

for Spray Polyurethane Foam Application

SPF Sprayer

Temporary Wall

Isolates (encloses) spray zone

Helper

Sprayed-on Foam

Air Supply

Air Exhaust

Direction of Work

Spray Zone

Air Exhaust Fan

Located in window or door

Air Supply Fan

(Or make-up air inlet)

Located on opposite side of spray area

Off-gassing Vapors

Figure 1. Establish air fl ow across the spraying area and draw overspray away from workers
EPA—WORKING DRAFT—6/29/11 Page 4 www.epa.gov/dfe 

Related tips:

■ Particulate exhaust fi lters should be used to remove SPF 

dusts and mists from the exhaust air. This not only helps 

to minimize hazardous air contaminants in the exhaust air 

but can also prevent SPF from settling on nearby vehicles 

or other property. Note that SPF can also buildup on the 

exhaust fan blades signifi cantly reducing the exhaust fan’s 

effi ciency over time. For this reason, the exhaust fi lter 

should be installed in front of the fan to remove the dusts 

and mists before they reach the fan. Clogged fi lters can 

also reduce effi ciency, so remember to follow the fi lter 

manufacturer’s recommendations for fi lter replacement.

■ Some SPF vapors and mists can present explosion 

hazards at certain concentrations. As a result, you may 

need to use a fan rated for use in explosive environments. 

Check with SPF manufacturer to determine if certain uses 

of the product pose this hazard.

Ensure Adequate Ventilation 

Following Application 

Always remember to continue ventilating the area following 

application until the material has fully cured, off -gassing has 

stopped, and vapors have been removed. During this time, 

worker re-entry should be kept to a minimum and should only 

include those with appropriate respiratory protection (and 

skin protection if contact with the SPF is possible). Occupant 

re-entry should only occur after the building is fully ventilated. 

The amount of time needed for this depends on several factors including:

■ SPF formulations and related cure times as specifi ed by 

the manufacturer 

■ Accurate proportioning and mixing of A-side and B-side

■ Ventilation rate

■ Temperature and humidity

Check with the manufacturer of your SPF product to determine an appropriate re-occupancy time and ventilation rate. 

How Can I Get More Information on SPF 

ventilation and other important health 

and safety practices?

■ Talk to your SPF product manufacturer or vendor. 

■ Consult the National Institute for Occupational Safety and 

Health (NIOSH) by either calling 1-800-CDC-INFO or by 

visiting their website at 

http://www.cdc.gov/niosh/topics/isocyanates/

■ Visit the following websites:

❑ EPA’s Design for the Environment (DfE) SPF website at

http://www.epa.gov/dfe/pubs/projects/spf/spray_polyurethane_foam.html

❑ NIOSH Alert on Spray-on Truck Bed Lining Operations at

http://www.cdc.gov/niosh/docs/2006-149/default.html

❑ OSHA’s isocyanates website at

http://www.osha.gov/SLTC/isocyanates/index.html

❑ American Chemistry Council—Center for the 

Polyurethanes Industry (CPI) website at 

http://www.polyurethane.org/

❑ Spray Polyurethane Foam Alliance’s website at 

http://www.sprayfoam.org/

❑ OSHA’s Green Jobs Hazards website at

http://www.osha.gov/dep/greenjobs/index.html

Ongoing research at NIOSH and the CPI will continue to provide updated information on appropriate ventilation rates and 

isolation and capture methods.

Ventilation Guidance

for Spray Polyurethane Foam Application

Figure 2. Poor design of entryway short circuits ventilation and creates dead space

SPF Sprayer

Air Exhaust Fan Spray Zone

Located in window or door

Make-up Air Inlet

(Window or other opening)

Temporary Wall

Isolates (encloses) spray zone

Air Supply

Dead

Space

Enclosure Opening

Air Exha

Located in window 

re Opening

PF Sprayer

up Air Inlet

dow or other openin