Table of Contents Introduction 

Use of Amine Catalysts in 

Polyurethanes Manufacture

Polyurethanes are generally made by reacting a 

diisocyanate, such as toluene diisocyanate (TDI) or 

methylene diphenyl diisocyanate (MDI), and a blended 

polyol. When a polyurethane foam is desired, the 

process uses additional chemicals, such as amine and/

or metallic salt catalysts, auxiliary blowing agents, and 

silicone surfactants, to achieve the desired properties.

Amine catalysts are used to control and/or balance both 

the gelling reaction and the gas-forming or foaming 

reaction responsible for foam formation. Although 

several organometallic compounds or salts may be 

used as catalysts in the production of polyurethanes, 

many polyurethane manufacturers use either tertiary 

aliphatic amines or alkanolamines. Amine catalysts are 

typically 0.1 to 5.0 percent of a polyurethane formulation.

Chemical Composition

Amine catalysts are a class of organic compounds 

derived from ammonia (NH3) by substituting one or 

more of the hydrogen atoms with alkyl groups (carbon 

and hydrogen containing molecular chains)—e.g., 

dimethylcyclohexylamine [(CH3)2NC6H11]. An amine is 

primary, secondary, or tertiary depending on whether 

one, two, or three of the hydrogen atoms of ammonia 

are replaced. Most amines are basic and can combine 

readily with acids to form salts, some of which are 

useful as delayed-action catalysts. Catalytic activity of 

ISSUE AX173 • JULY 2011

Working with 

Polyurethane 

Foam Products

During New Construction, 

Retrofit and Repair

Fire Safety 

Guidance
2 Fire Safety Guidance

Fire Safety Guidance

Fire is a serious concern during construction, repair and retrofit projects 

because materials can be exposed to ignition sources. For example, there 

may be a potential for polyurethane/polyisocyanurate foam to be exposed 

to open flame from welding, cutting torches, and other ignition sources 

from allied trades during certain construction sequences. While fires 

involving polyurethane or polyisocyanurate foam during construction, 

retrofit or repair are rare, they do happen. The following safety 

precautions, limited here to a discussion of polyurethane and 

polyisocyanurate foam products that are present during “hot work,” 

are suggested for the construction site to help prevent these accidents. 

However, if a fire does occur and cannot be extinguished immediately, 

evacuate the area at once. Any guidance or suggestions made in this document do 

not replace the instructions provided by the employer, the MSDS and the product 

instructions.

Trade Performing “Hot Work”

OSHA defines Hot Work as riveting, welding, flame cutting or any other fire or sparkproducing operation (See 29 CFR § 1910.252a)

• OSHA states that “hot work” permits must be authorized by an individual 

designated by management and only after a “hot work” assessment has been 

completed. It also states that the person performing the “hot work” is not 

authorized to make such assessments or issue permits. 

• Thoroughly educate other trades on the site about fire characteristics of 

polyurethane or polyisocyanurate foam. Refer to the foam manufacturer’s 

literature for safety recommendations.

• If possible, perform “hot work” in a designated area free of combustibles. 

• If “hot work” must be performed in an area where there are combustibles, move 

the combustibles, if possible, a distance of at least 35 feet from the “hot work,” as 

required by OSHA. If the combustibles cannot be moved, shield the combustibles 

with a fire retardant cover. 

• A fire watch is required by OSHA (see 29 CFR 1910.252(a) (2)(iii)) where: 

» combustible building materials or contents are closer than 35 feet to the 

point of operation; 

» wall or floor openings within a 35-foot radius expose combustible materials 

in adjacent areas, including concealed spaces in walls or floors; 

» combustible materials are adjacent to the opposite side of partitions, walls, 

ceilings, or roofs and are likely to be ignited; or 

» any other criteria are applicable as listed by OSHA under 29 CFR § 1910.252a 

(Fire Prevention and Protection). 

OSHA defines Hot 

Work as riveting, 

welding, flame cutting 

or any other fire or 

spark-producing 

operation (See 29 CFR § 

1910.252a)
3 Fire Safety Guidance Fire Safety Guidance

Contractor

• Conduct job safety meetings with all other trades in order to develop a safety plan 

before, during and after polyurethane or polyisocyanurate application. Review 

foam manufacturer’s installation instructions for safety recommendations.

• For retrofit or repair projects, determine whether foam products are present 

before any hot work is performed. If so, follow the same fire prevention 

procedures as for new construction.

• If foam insulation is being installed near potential ignition sources, a fire watch may 

be required (see Trade Performing “Hot Work” Section for fire watch discussion). 

• Provide warning signs and labels on the job site where the trades performing hot 

work are most likely to see them, as required by 29 CFR § 1910.145 and 29 CFR § 

1910.252. 

• Do not allow smoking on the job site.

• Schedule application of required thermal barrier as soon as practically possible.

• Keep other trades from working in the application area until a thermal barrier is 

applied over the foam. If another trade must work in the area before the thermal 

barrier is applied, they should determine if a fire watch is required (see Trade 

Performing “Hot Work” Section for fire watch discussion). 

For Spray Polyurethane Foam Contractors

• Review the manufacturer’s installations instructions concerning the thickness 

of the foam per pass, because the SPF may scorch or ignite when installed too 

quickly to achieve the desired thickness or installed in too thick a pass.

All Trades

If a fire occurs that cannot be extinguished immediately, evacuate the area at once. 

• Have an adequate supply of suitable fire extinguishers in convenient locations. 

Personnel that use extinguishers must be trained in their use. (Note: 

Polyurethane and polyisocyanurate foam typically require carbon dioxide and dry 

chemical extinguishers) 

• Avoid accumulating large amounts of combustible waste materials (for example, 

foam trim and paper). Observe good housekeeping practices, and dispose of 

waste properly.

• Do not smoke on the job site.

If a fire occurs that 

cannot be extinguished 

immediately, evacuate 

the area at once
4 Fire Safety Guidance

Additional Fire Safety Information: 

Rigid polyurethane or polyisocyanurate foams will, if ignited, release various products 

of combustion such as smoke and gases that may be irritating, flammable and/or 

toxic. As with other organic materials, such as wood, the primary combustible gases 

are carbon dioxide and carbon monoxide. 

• Fire Safety Guidelines for Use of Rigid Polyurethane or Polyisocyanurate Foam 

Insulation in Building Construction 

Center for the Polyurethanes Industry 

http://www.polyurethane.org/s_api/sec.asp?CID=1649&DID=11363

• AY 126: Thermal Barriers for the Spray Polyurethane Foam Industry 

Spray Polyurethane Foam Alliance 

http://www.sprayfoam.org/downloads/pdf/AY%20126.pdf 

• NFPA 51 B, Fire Prevention During Welding, Cutting and Other Hot Work

National Fire Prevention Association 

http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=51B 

• OSHA Regulation 29 CFR § 1910.252 Welding, Cutting, and Brazing 

ttApplication Standard

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9853

• Tech Tip Spray Polyurethane Foam – Exotherm vs. Thickness

Spray Polyurethane Foam Alliance 

http://www.sprayfoam.org/uploads/pages/4480/Tech%20Tip%20Exotherm.pdf

Legal Notice: This guidance document was prepared by the American Chemistry Council’s Center for the 

Polyurethanes Industry. It is intended to provide general information to professional persons who may be involved 

in installing polyurethane foam in new construction, retrofit or repair projects. It is not intended to serve as a 

substitute for in-depth training or specific construction requirements, nor is it designed or intended to define 

or create legal rights or obligations. It is not intended to be a “how-to” manual, nor is it a prescriptive guide. All 

persons involved in construction projects including polyurethane foam have an independent obligation to ascertain 

that their actions are in compliance with current federal, state and local laws and regulations and should 

consult with legal counsel concerning such matters. The guidance is necessarily general in nature and individual 

companies may vary their approach with respect to particular practices based on specific factual circumstance, 

the practicality and effectiveness of particular actions and economic and technological feasibility. Neither the 

American Chemistry Council, nor the individual member companies of the Center for the Polyurethanes Industry 

of the American Chemistry Council, nor any of their respective directors, officers, employees, subcontractors, 

consultants, or other assigns, makes any warranty or representation, either express or implied, with respect 

to the accuracy or completeness of the information contained in this guidance document; nor do the American 

Chemistry Council or any member companies assume any liability or responsibility for any use or misuse, or the 

results of such use or misuse, of any information, procedure, conclusion, opinion, product, or process disclosed in 

these Guidelines. NO WARRANTIES ARE GIVEN; ALL IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS 

FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED.

This work is protected by copyright. Users are granted a nonexclusive royalty-free license to reproduce and 

distribute these guidelines, subject to the following limitations: (1) the work must be reproduced in its entirety, 

without alterations; and (2) copies of the work may not be sold.

For more information on material presented in these Guidelines, please contact your supplier. 

Copyright © October 2011, American Chemistry Council.
5 Fire Safety Guidance Fire S

Fire Safety Guidance

Working with Polyurethane Foam Products During 

New Construction, Retrofit and Repair

1

MEET:

Conduct a safety 

meeting with other 

trades.

2

POST:

Put up warning 

signs at the site.
6 Fire Safety Guidance

3

MOVE:

Move combustibles 

away from the “hot 

work” site.

4

SHIELD:

Shield combustibles 

with fire blanket or 

welder’s blanket.
7 Fire Safety Guidance Fire Safety Guidance 5

WATCH:

Provide fire watch if 

necessary. Have appropriate 

fire extinguisher and 

telephone nearby. Evacuate 

area if fire cannot be 

extinguished immediately. 6

PROTECT:

Protect installed foam with 

a required thermal barrier 

such as 1⁄2 in gypsum board 

as soon as possible. 
700 2nd Street NE Washington, District of Columbia 20002-4308

www.americanchemistry.com/polyurethane

October 2011 AX426