Studies and 

Research Projects

Chemical substances and biological agents

Research Projects

REPORT R-629

4,4’-Diphenylmethane diisocyanate (MDI)

Safety practices and concentration

during polyurethane foam spraying

Brigitte Roberge

Rodrigue Gravel 

Daniel Drolet
Established in Québec since 1980, the Institut de recherche 

Robert-Sauvé en santé et en sécurité du travail (IRSST) 

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2009

ISBN: 978-2-89631-411-9 (print format)

ISBN: 978 ISBN: 978-2-89631-412-6 (PDF) 6 (PDF)

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Institut de recherche Robert-Sauvé

en santé et en sécurité du travail,

November 2009
Studies and

Research Projects

Chemical substances and biological agents

REPORT R-629

Research Projects

4,4’-Diphenylmethane diisocyanate (MDI)

Safety practices and concentration

during polyurethane foam spraying

Disclaimer

The IRSST makes no guarantee

regarding the accuracy, reliability

or completeness of the information

gp y p y g

Brigitte Roberge, Rodrigue Gravel and Daniel Drolet

IRSST or completeness of the information

contained in this document. In no

case shall the IRSST be held

responsible for any physical or

psychological injury or material

damage resulting from the use of

this information.

Note that the content of the documents is protected by Canadian

intellectual property legislation.

This publication is available free

of charge on the Web site.

This study was financed by the IRSST. The conclusions and recommendations are those of the authors.
The results of the research work published 

in this document have been peer-reviewed.

IN CONFORMITY WITH THE IRSST’S POLICIES
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

i

ACKNOWLEDGMENTS 

The authors would like to thank Claude Létourneau, Yves Beaudet, Renaud Daigle and Pierre Drouin of the IRSST 

for their field work; Lucile Richard and Marielle Carrier of the IRSST for the analysis of laboratory samples; 

Laurent Gratton of the IRSST for the follow-up of the promotion and transfer of the IRSST's research results; 

Bernard Teasdale, consultant from ASP Construction; and the polyurethane foam insulation contractors and their 

employees that we met. 

The authors would like to thank the ACC Center for the Polyurethanes Industry for the translation. 

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

iii

ABSTRACT 

In recent years, some Québec construction workers have been "sensitized" to 4,4'-

diphenylmethane diisocyanate (MDI). This substance is emitted during spraying of a 

polyisocyanate (a mixture of MDI polymers) and a polyhydroxyl compound (resin) to form a 

rigid polyurethane foam used for thermal insulation in buildings. The permissible exposure value 

(PEV) for MDI (monomer form) in Québec is 0.051 mg/m3 (51 μg/m3). This substance has been 

identified as a sensitizer (S) in the Regulation respecting occupational health and safety 

(RROHS) (Règlement sur la santé et la sécurité du travail RSST), which also mentions that the 

exposure should be kept at a minimum (ME). 

Field studies (on-site spraying) reported in the scientific literature have shown significant 

concentrations of MDI during this process, particularly in the residential construction sector. In 

fact, the Lesage study (2007) confirmed the need to sample MDI aerosols and to use a collection 

medium that allows their optimal collection, considering the short polymerization time in this 

process. 

The Canadian Urethane Foam Contractors Association (CUFCA) and the Alliance for the 

Polyurethane Industry (API) offer a training program for installers (or appliers) of this foam. The 

program covers the spraying methods available to obtain a quality product, which will therefore 

depend on the workers’ skill. The safety aspect during spraying operations is hardly or not 

addressed at all. 

Initially, this study documented occupational health and safety practices under a wide range of 

conditions where insulation work is carried out, including commercial or residential 

construction, the location of the work (indoors or outdoors), and the season (summer or winter). 

The study then evaluated MDI by means of stationary sampling in the work areas. These 

concentrations (average concentration over the duration of the work and weighted over an 8-hour 

period, TWAEV) were analyzed according to the determining factors influencing the workers' 

exposure to MDI. The details of the work were examined in order to estimate, with a fair degree 

of confidence, the highest risk scenarios during foam spraying operations. The risk of exposure 

to MDI in monomer form (aerosols) for workers performing spraying operations is high, 

particularly when such operations are performed indoors where the average of the concentrations 

in the spraying zone reach 288 μg/m3

. In addition to these characteristics, individual and team 

(team consisting of an installer (or applier) and his assistant) work practices explain certain 

variations in the data collected. 

Despite the training program for installers (or appliers) offered by an accreditation authority, 

nothing indicates that occupational health and safety practices are being completely followed on 

Québec construction sites. In the context of competency training, occupational health and safety 

practices as well as respiratory and skin protection need to be rigorously addressed and should be 

part of the workers' continuing training process. 

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

v

TABLE OF CONTENTS 

ACKNOWLEDGMENTS ............................................................................................................... i 

ABSTRACT ................................................................................................................................... iii 

TABLE OF CONTENTS .................................................................................................................v 

LIST OF TABLES ........................................................................................................................ vii 

LIST OF FIGURES ..................................................................................................................... viii 

1. INTRODUCTION ..................................................................................................................1 

2. ISSUES AND STATE OF KNOWLEDGE ...........................................................................3 

2.1 Effects on health and prevalence ...................................................................................3 

2.2 Principal uses .................................................................................................................4 

2.3 Documented levels of exposure .....................................................................................4 

2.4 Training ..........................................................................................................................5 

3. RESEARCH OBJECTIVES ...................................................................................................7 

4. METHODS .............................................................................................................................9 

4.1 Analytical methods ........................................................................................................9 

4.2 Sampling strategy.........................................................................................................10 

5. RESULTS .............................................................................................................................13 

5.1 Description of sites ......................................................................................................13 

5.2 Work organization .......................................................................................................13

5.3 Health and safety practices ..........................................................................................14 

5.3.1 Work zone approach equipment ......................................................................15 

5.3.2 Respiratory protection ......................................................................................16 

5.3.3 Protective clothing............................................................................................17 

5.4 Ergonomic hazards.......................................................................................................18 

5.5 Chemical hazards .........................................................................................................19 

5.5.1 Analytical results and average MDI concentrations ........................................21 

5.5.2 Other exposure risks ........................................................................................24 
vi (Cliquez ici pour le titre du rapport) - IRSST

6. DISCUSSION .......................................................................................................................25 

6.1 Work organization .......................................................................................................25

6.2 Health and safety practices ..........................................................................................25 

6.2.1 Hoisting equipment ..........................................................................................25 

6.2.2 Protective equipment .......................................................................................26 

6.3 Ergonomic hazards.......................................................................................................27 

6.4 Chemical hazards .........................................................................................................27 

6.4.1 MDI concentration in the spraying zone ..........................................................27 

6.4.2 MDI concentration outside the spraying zone .................................................28 

6.4.3 Post-spraying MDI concentration ....................................................................29 

6.4.4 Statistical analysis ............................................................................................30 

6.5 Other risks of exposure ................................................................................................31 

6.6 Recommendations ........................................................................................................31 

7. CONCLUSION .....................................................................................................................33 

REFERENCES ..............................................................................................................................35 

APPENDIX 1: LIST OF POINTS RELATING TO WORK METHODS ....................................39 

APPENDIX 2: LIST OF PRODUCTS USED ...............................................................................45 

APPENDIX 3: ANALYTICAL RESULTS...................................................................................49 

APPENDIX 4: DATA FROM THE STATISTICAL ANALYSIS OF THE MDI RESULTS ....57 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

vii

LIST OF TABLES 

Table 1: Description of the MDI analysis methods .......................................................................10 

Table 2: Work zone approach equipment used on the sites visited ...............................................15 

Table 3 : Respirators used ..............................................................................................................17 

Table 4: Protecting clothing ...........................................................................................................17 

Table 5: Brief description of surveys for each team of workers ....................................................20 

Table 6: Inside the spraying zone : Average MDI concentrations per installer .............................22 

Table 7: Outside the spraying zone : Average MDI concentrations per assistant .........................22 

Table 8: Average MDI concentrations by zone by location/season ..............................................23 

Table 9: Average MDI concentrations by zone for indoor work ...................................................23 

Table 10: Average MDI concentrations in the area outside the spraying zone .............................23 

Table 11: Average monomer MDI concentrations: post-spraying by floor ...................................23 

Table 12: Average concentrations of monomer MDI by task ........................................................27 

Table 13: Good practices recommended and poor practices observed ..........................................29 
viii (Cliquez ici pour le titre du rapport) - IRSST

LIST OF FIGURES 

Figure 1: Causal agents for compensated occupational asthma disorders in 2007 ..........................3

Figure 2: Sampling stations during spraying of indoor surfaces ...................................................10

Figure 3: Sampling stations during spraying of outdoor surfaces .................................................11

Figure 4: Non-compliant shelter on a motorized elevating platform .............................................16

Figure 5: Spray gun and jet (Pierre Charbonneau, photographer) .................................................18

Figure 6: Crouching position (Pierre Charbonneau, photographer) ..............................................19

Figure 7: Average of the monomer MDI concentrations in post-spraying samples ......................24

Figure 8: Position of worker on a rung of a stepladder (Pierre Charbonneau, photographer) ......25

Figure 9: Protection of vertical members and cross members of hoisting equipment ...................26
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

1

1. INTRODUCTION 

In industrialized countries, among all exposed workers, the percentage of workers sensitized to 

MDI is around 5 to 10% (Nadeau 2000). MDI is emitted in the form of small aerosols (monomer 

and oligomer droplets) (Lesage and Ostiguy 2000) during the rigid polyurethane foam (insulating 

foam) spraying process on construction sites. It is identified as a sensitizer (S) in Schedule I of 

the Regulation respecting occupational health and safety (RROHS). Moreover, a regulation1

modifying the Safety Code for the Construction Industry (SCCI) and the RROHS (article 42), in 

effect since March 2008, mention, in particular, protection and the reduction of exposure to a 

minimum for diisocyanates or isocyanate oligomers. 

The scope of this study was to document hazardous practices and to evaluate the work 

environment in terms of MDI concentrations (monomer and oligomers), in stationary sampling, 

during spraying work (aerosols and vapours) and post-spraying (vapours) on Québec 

construction sites based on the work being carried out. 

The distinctive feature of this field study was the variety of situations investigated where a 

spraying process involving a polyisocyanate (a mixture of MDI polymers) and a 

polyhydroxylated compound (resin) is used (thermal insulation process), and the occupational 

safety aspect during this work. In fact, studies reported in the scientific literature had not dealt 

with occupational health and safety practices, and had mainly targeted residential construction. 

The first sections of this report cover the current state of knowledge, the objectives, and the 

evaluation strategy (sampling and analysis) used within the framework of this field study. The 

observations and analytical results are reported in section 5 and discussed in section 6. 

 

1 1 C.S2-1, r19.01, section 1 article 2. {On line}. 

http://www.csst.qc.ca/NR/rdonlyres/A689E06B-EBA7-40FE-A55A-EBAF1239FC21/4177/DC_200_1027.pdf

http://www2.publicationsduquebec.gouv.qc.ca/dynamicSearch/telecharge.php?type=2&file=%2F%2FS_2_1%2FS2

_1R19_01.htm (April 2008)

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

3

2. ISSUES AND STATE OF KNOWLEDGE 

2.1 Effects on health and prevalence 

According to Commission de la santé et de la sécurité du travail (CSST, workers’ compensation 

board) statistics, compensation is paid out for 40 to 60 new cases of occupational asthma every 

year. Around 250 substances are recognized as being causal agents for occupational asthma 

(OA).2

 As illustrated in Figure 1, 17% of all OA cases recognized in 2007 have as their causal 

agent a substance from the isocyanate family. Certain substances in this family are chemical 

irritants for the respiratory tract, eyes and skin, and are respiratory and skin sensitizers. 

Occupational exposure to isocyanates may induce rhinitis, which could develop into OA. These 

two respiratory disorders of occupational origin manifest themselves through the appearance of 

symptoms following repeated exposure to a sensitizing agent. These symptoms diminish or 

disappear a short time after the worker leaves the work environment. According to 

pneumologists (Bernstein et al. 1999), a worker sensitized to isocyanates may react immediately 

or several hours after exposure, even at very low concentrations, even lower than 1 ppb for short 

intervals. This allegation is also reported by other authors (Nadeau 2000, and Ostiguy et al. 

2005). 

Figure 1: Causal agents for compensated occupational asthma disorders in 2007 

In numerous work environments, concentrations of monomer isocyanates have been reduced or 

controlled by engineering or administrative means or by the wearing of respiratory protection. 

Nevertheless, it seems that there are still cases of sensitization. Oligomers (polyisocyanates) 

contain isocyanate functions that have characteristics similar to those of monomers. They may 

also contribute to the toxicity of isocyanates (Bernstein and al. 2006). Researchers (Karol et al. 

1981) have shown that skin contact exposure to isocyanates (particularly TDI) in animals could 

have a sensitizing effect on subjects, leading to an asthmatic reaction during inhalation exposure. 

Some claim that skin exposure alone cannot be the only cause of an asthmatic reaction (Dhimiler 

2007, Vanoirbeek and al. 2004, Herrick and al. 2002, and Karol and al. 1981). Although there is 

no consensus on the subject, it would seem that the skin is a route of exposure that could lead to 

respiratory sensitization among workers. 

 

2

 {Online}. {http://www.reptox.csst.qc.ca/Documents/PlusEncore/Asthme/Htm/Asthme.htm#Chap3} (April 2008). 

1 7%

17 %

13% 9 % 9%

9 %

7%

11%

9%

Isocya na te s

Wood dusts

Seaf ood

Weld in g fumes

A nimals

Cere al dusts

Epox y, resins, glues

Not specif ied
4 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

2.2 Principal uses 

Substances in the isocyanate family enter into the synthesis of a wide range of polymers with 

different properties. According to Streicher et al. (2000), these polymers are involved in the 

manufacture of commercial mixtures such as paints, flexible and rigid foams, adhesives, resins 

and elastomers. In addition to the workers employed in the manufacture of these mixtures, other 

people may also come into contact with isocyanates during their use in the work environment, in 

particular during on-site spraying to form the rigid polyurethane foam used for insulation 

purposes on construction sites. 

Diisocyanates, called monomers, and polyisocyanates, called oligomers, can form polymers by 

combining with other molecules. Diisocyanates can contain a proportion of monomer varying 

from 25 to 76%3

 (Ostiguy et al. 2005). During insulation work, a mixture comprised of a 

polyisocyanate (mixture of MDI polymers) and a polyhydroxylated compound called polyol 

(resin) is sprayed on surfaces by means of a spray gun. Several companies manufacture these 

products, including polymeric MDI (PMDI), which is marketed under different names such as 

Lupranate®, Rubinate®, Desmodur®, Voranate®, Caradate®, etc. (INERIS 2002). The PMDI 

used in this process consists of 45-55% polymethylenepolyphenylene diisocyanate and 45-55% 

4,4'-diphenylmethane diisocyanate. Due to its low vapour pressure at ambient temperature 

(<0.00001 mm Hg), it can be found in the air mainly in the form of aerosols (monomer and 

oligomers). The resin contains, in addition to polyol, a blowing agent causing the foam to 

expand, and additives such as stabilizers that prevent its deterioration. Resin manufacturers offer 

two versions, regular and winter, to allow spraying of the foam in winter by modifying the 

concentration of some of its components. 

According to Abecassis (2000), the products cited above react in three phases to form 

polyurethane foam: 

1. Mixing and creaming time: approximately 5 seconds; 

2. Expansion or inflation time (exothermic reaction and expansion of the foam): 15 to 20 

seconds; 

3. Polymerization or hardening (alveolar structure): 2 to 3 minutes. This phase is totally 

completed 48 hours after spraying. 

It is therefore important to make sure that the sampling methods and the collection medium take 

the rapid polymerization of this process into account and that the analytical methods can quantify 

the monomer and oligomer aerosols (Lesage et al. 2007, Lesage and Ostiguy 2000). 

2.3 Documented levels of exposure 

Although several recent articles discuss the exposure to isocyanates in the factory production of 

flexible foam where toluene diisocyanate (TDI) is used, few discuss the MDI exposure of 

workers in the construction sector (Research and Development Department, Construction Safety 

Association of Ontario 1987, Hosein and Farkas 1981, Bilan and al. 1989, Crespo and Galan 

1999, Creely and al. 2006, and Lesage and al. 2007). These articles report significant 

 

3

 {On line} http://www.irsst.qc.ca/fr/isocya_7.htm (April 2008). 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

5

concentrations during this polyurethane foam spraying operation: for installers (or appliers), 

from 0.017 to 0.4 mg/m3

, and for their assistants, from 0.01 to 0.31 mg/m3. Although these 

concentrations do not correspond to a time-weighted average exposure value (TWAEV) over 8 

hours, several exceed the regulations prevailing in Québec where the TWAEV for MDI 

(Schedule I, RROHS) is 0.051 mg/m3

 (51 μg/m3) or 0.005 ppm for the monomer form with 

mention of reduction of exposure to a minimum (EM). 

2.4 Training 

In Canada, the practice of this skilled activity involving polyurethane foam spraying is governed 

by a training program of the Canadian Urethane Foam Contractors Association (CUFCA)4

 and 

by the Alliance for the Polyurethane Industry (API) in conformity with the standard CAN/ULCS705.25

 of the Underwriters’ Laboratory of Canada (ULC).6 The challenge is to communicate 

knowledge and to ensure that installers (or appliers) reach the necessary level of expertise for 

this task. Moreover, companies distributing commercially available mixes must certify installers 

(or appliers) in the use of their products, and in the particular requirements of the products, etc. 

This program only involves the work itself. The occupational health and safety (OHS) aspect is 

very limited. 

The Québec market is mainly served by two companies that distribute commercial mixes. These 

companies have quality standards for the foam, and safety warnings for spraying. The 

occupational safety aspect in the context of this training is hardly or not covered at all. There are 

85 Québec contractors that are members of CUFCA.7

 However, the number of qualified workers 

is not documented on this site. 

 

4

 {On line}. {http://www.cufca.ca/training/levels_e.php} (April 2008). 5

 The Canadian standard CAN/ULC S705.1 lists the requirements for liquid components, contractors and installers. 

The CAN/ULC S705.2 standard sets the requirements for environmental conditions and other relevant 

documentation on spraying. 

6 {On line}. {http://www.ulc.ca/ABOUT_ULC/Work_program.asp} (April 2008). 7

 {On line}. {http://www.cufca.ca/lookup/search_e.php} (November 2008). 

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

7

3. RESEARCH OBJECTIVES 

The objectives of this study are to: 

• Document the practices, based on the working methods prescribed by the training 

program, for the spraying of polyurethane foam; 

• Document good practices in terms of occupational health and safety and hazardous 

practices during spraying work on Québec construction sites based on the different tasks 

carried out; 

• Evaluate the working environment in terms of MDI concentrations (monomer and 

oligomers) by means of stationary sampling during foam spraying operations (aerosols 

and vapours) and post-spraying (vapours). 

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

9

4. METHODS 

In order to fulfill the study’s first objective, points relating to the work methods (see Appendix I) 

were listed from the documentation for the training program for polyurethane foam installers (or 

appliers). In order to fulfill the second objective, these points were validated in the workplace in 

relation to the reality in which the workers (installers and assistants) carry out the spraying 

operation on different Québec construction sites. 

The study targeted new construction sites and/or sites undergoing renovation, both residential 

and commercial, where the indoor (basement walls, belts) or outdoor structural elements were 

insulated with polyurethane foam in winter and in summer. The list of contractors using this 

foam was developed from the list of Québec thermal insulation contractors8

 (under categories 

4231 and 4232) and that of CUFCA.9

4.1 Analytical methods 

The sampling train recommended in method 25/3 Organic Isocyanates in Air of the Health and 

Safety Executive (HSE)10 was used for quantifying MDI aerosols and vapours in the form of 

monomers and oligomers. This method allows the aerosols emitted to be collected by an 

impinger in a solution before polymerization (which occurs very rapidly in this process) is 

complete (Lesage and al. 2007, Abecassis 2000). This method was therefore preferred over the 

one in which the aerosol collection medium is a pre-treated glass fiber filter that is placed in a 

reagent solution after the 15-minute sampling.11 This collection medium, used according to the 

IRSST’s laboratory specifications, is not suitable for a process in which polymerization takes 

place rapidly. 

Sampling for aerosols and for quantifying MDI vapours in monomer form according to the 

Institut de recherche Robert Sauvé en santé et en sécurité du travail (IRSST) high sensitivity 

(HS) method was performed at a rate of 1 L/min. over a period of 30 to 60 minutes, depending 

on the duration of the work or the area to be sprayed. These samples were therefore collected 

consecutively over the total spraying period on one construction site for one survey. The 

analytical methods are summarized in Table 1. The coefficient of variation for the samples was 

5%. 

 

8 {On line}. 

{http://w3.rbq.gouv.qc.ca/rbq/owa/RBAC2.aff_liste?p_session=3179754&p_alpha=TOUS&P_type_rech=E&P_nbre

=630} (April 2008). 

{http://w3.rbq.gouv.qc.ca/rbq/owa/RBAC2.aff_liste?p_session=3179754&p_alpha=TOUS&P_type_rech=E&P_nbre

=308} (April 2008). 

{http://w3.rbq.gouv.qc.ca/rbq/owa/RBAC2.aff_liste?p_session=3179754&p_alpha=TOUS&P_type_rech=E&P_nbre

=799} (April 2008). 9

 {On line}. {http://www.cufca.ca/lookup/search_e.php} (November 2008). 10 Methods for Determination of Hazardous Substances HSE {On line}. {http://www.hse.gov.uk/pubns/mdhs/pdfs/mdhs25-3.pdf} 

(April 2008). 

11 {On line}. http://www.irsst.qc.ca/files/documents/fr/Labos/Isocyanates1.pdf (February 2009). 
10 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

Table 1: Description of the MDI analysis methods 

25/3 Organic Isocyanates in Air IRSST High Sensitivity 

Analysis/detection HPLC-UVF HPLC and MS/MS 

Collection medium Impinger system containing a 

MOPIP solution 

37 mm membrane impregnated with 

MAMA 

LOQ: monomers

oligomers

0.036 μg 

0.041 μg 

0.00075 μg 

- - - - 

ACV 2.8% < 5% 

HPLC-UVF: High pressure liquid chromatography with ultraviolet and fluorescence detection 

HPLC: High pressure liquid chromatography MS/MS: Double mass spectrometry 

MOPIP: methoxy-2-phenyl-1-piperazine MAMA: 9-(N-methylaminomethyl) anthracene 

LOQ: Analytical limit of quantification ACV: Analytical coefficient of variation 

4.2 Sampling strategy 

Stationary sampling of MDI (monomer and oligomers) was carried out in the spraying zone 

(installer or applier) and in the areas outside the spraying area (assistant and workers from other 

specialties). In the spraying zone, two sampling trains (aerosols and HS vapours) framed the 

installer (approximately 2 metres on each side and at a height of 1.5 metres - see Figures 2 and 

3). An average of their analytical results was used to estimate the average concentration in this 

zone. For the zones outside the spraying area, sampling trains were positioned approximately 

3 metres behind the installer (HS vapours and aerosols) (assistant’s work area) or at the centre of 

the floor where the spraying work was being carried out (working area of workers from other 

trades). For outdoor work, a sampling train was positioned approximately 2 m downstream from 

the spraying zone in terms of wind direction (see Figure 3). During outdoor work, if there had 

been workers inside the building, HS vapours would also have been sampled. 

 

 

L eft 

Installer (or applier)

Right 

Periphery-assistant

Figure 2: Sampling stations during spraying of indoor surfaces 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

11

Figure 3: Sampling stations during spraying of outdoor surfaces 

Finally, post-spraying samples (HS vapours) were collected for two hours (from 0 to 30 minutes, 

from 30 to 60 minutes, and from 60 to 120 minutes) following completion of the work. They 

were located at the centre of the floor where the work was carried out and on the floor above. 

They targeted the detection of residual MDI vapours over time. 

The analytical results and information collected on the construction sites were entered in a 

database (DB) created in Microsoft Excel software. The collected information was, among other 

things, the resin used, the thickness sprayed, the season during which the work was carried out, 

the location (indoors or outdoors), the time of the sampling (during spraying or post-spraying), 

the protective equipment, the scaffolding equipment (stepladder, stationary or mobile platform, 

with articulated arm, etc.) and the analytical results. 

The data relating to the monomer form were analyzed statistically with IHSTAT software12 from 

the American Industrial Hygiene Association (AIHA) in order to validate the similar exposure 

group (SEG) and to document MDI exposure. Here, SEG is defined as a set of exposure 

determining factors for which the exposure to monomer MDI would be similar. Therefore the 

analysis aims to estimate, with a certain degree of confidence, the most hazardous determining 

factor(s) for the tasks targeted during foam spraying operations. The parameters retained were 

the daily average exposure value (DAEV) and the average concentration of the samples by 

survey and by task. They were considered in relation to three situations: 1) location of the work 

(indoors or outdoors), 2) season (summer or winter), and 3) the type of foam used (regular or 

winter resins). This treatment was also applied to the data on oligomers. 

 

12 Free software https://www.aiha.org/1documents/committees/EASC-IHSTAT.xls (January 2009). 

Wind direction Downstream Left 

Installer (or applier) 

Right 

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

13

5. RESULTS 

The study results that are documented in this report relate to 1) a description of the construction 

sites visited, 2) work organization, 3) special features of the construction sites, 4) occupational 

health and safety practices involving hoisting equipment and protective equipment, 5) ergonomic 

hazards, and 6) chemical hazards (for health) and the MDI exposure risk factors for the installers 

and their assistants and for other workers present on site. 

The list in Appendix I contains the information on points 1 to 4 above. 

5.1 Description of sites 

The sites visited were construction sites or renovation sites for residential buildings 

(condominiums, single family residences, cottages) and commercial buildings. Four foams were 

used by the contractors visited. Technically, the CAN/ULC-S705.2-05 standard describes the 

conditions during spraying: less than 17°C difference between the ambient temperature and that 

of the substrate, and a relative humidity of the ambient air below 80%. However, manufacturers 

of commercial products recommend the use of a specific mixture for cold temperatures and the 

installation of a temporary shelter to protect the spraying zone from rain, snow and wind. 

Our 20 surveys13 involved nine Québec thermal insulation contractors using polyurethane foam. 

These companies were members of prevention mutuals and had a prevention program. At least 

two surveys were carried out with each contractor and were classified as follows: 

• 7 sites: insulation of exterior walls of a commercial building 

• 1 site: insulation of exterior walls of a residence (condominium) 

• 2 sites: insulation of interior walls on several different floors, including a crawl space 

• 4 sites: insulation of the basement walls of a residence 

• 5 sites: sealing of belts. 

5.2 Work organization 

A work team consists of one installer and his assistant who can take turns spraying throughout 

the day. Generally there is one team per site. However, on one site, there were two teams of 

workers doing the spraying, and on two other sites, the installer worked alone without an 

assistant. Moreover, some installers we met had not yet followed their training program because 

they had to perform a certain number of hours of on-the-job work beforehand. 

For all the contractors we visited, the workers shared the work between them as follows: 

a) As soon as they arrived on site, the assistant started preparing the area (masking 

openings, the ground with plastic sheeting held in place with a product made of volatile 

organic compounds (VOCs) under pressure, staples or adhesive tape), preparing 

 

13 The term "survey" corresponds to one more or less complete day of sampling. 
14 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

equipment (compressor, hose, etc.). After the spraying work, he removed the sheeting 

and cleaned up the site. 

b) Cleaning of the gun, quality control of the foam and the thickness sprayed, the spraying 

angle and the operating conditions14 (temperature, humidity and wind speed) were the 

installer's responsibility. 

The working day, including transport time, began between 5:30 and 6:30 a.m. and could last 

until completion of the work. When atmospheric or winter conditions (rain, snow, cold 

temperatures, wind) made it necessary, the workers suspended the work or set up a protective 

structure with plastic sheeting (tent-style) on the ground or on the hoisting equipment used. 

The workers often ate in the box of the truck where barrels of resin and MDI were stored, 

without access to washrooms to wash their hands beforehand. A microwave oven was often 

available. 

Our discussions with the workers enabled us to draw a portrait of a typical working day 

(approximately 8 hours per day): 

1. Transport between the contractor's warehouse and the site 

2. Preliminary work: heating of spraying equipment, verification of hoisting equipment 

where necessary, masking, gun cleaning, etc. 

3. Spraying of the foam according to the customer's specifications, with breaks when 

needed, and a meal 

4. Masking removal and cleaning of the work site (often carried out while spraying was in 

progress) 

5. Transport to the contractor's warehouse if the working day was finished, or 

6. To another site where the operations described in points 2 to 5 were repeated. 

The duration of spraying in an 8-hour working day (480 minutes) varied between 180 to 230 

minutes or more, if more than one site was visited. Finally, the logistics of the work on certain 

sites were particularly chaotic, causing frequent interruptions for the spraying team. 

Although installers must be certified, they do not all have this certification. Two workers were 

scheduled to follow training courses in the months after our survey. Before obtaining their 

certification, they must perform a certain number of hours of practical experience in spraying. 

Eight contractors out of the nine we met were certified. 

5.3 Health and safety practices 

Several sites visited were cluttered with tools, materials, waste, etc. This clutter hindered the 

installer when moving the resin and MDI feed hose from place to place, among other things. The 

surfaces to be sprayed were not always easy to reach. Certain jobs, even though of short 

duration, were carried out in problem areas with difficult access (such as attics, attic spaces, etc.). 

Moreover, the workers sometimes had to enter an enclosed or confined space as described in 

 

14 The temperature of the primary heaters must be between 43° and 49°C (100° and 120°F) and that of the feed hose 

35° to 40°C (95° to 105°F), i.e., 5 to 15°F less than the heaters. 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

15

RROHS division 1 and SCCI subsection 1.1.17.1. One of the monitored teams proceeded to 

insulate the walls of a crawl space with restricted access, entering it by means of a stepladder 

borrowed from some other workers. These workers had not received the training prescribed in 

the RROHS and in SCCI article 3.21. Finally, workers often did not wear safety helmets. 

Frequently, workers from other construction specialties moved around or carried out work close 

to the spraying area. For example, a "hot" job (welding) was being done next to the spraying 

zone of one of the sites visited, without an isolation barrier on the foam. This practice is 

forbidden unless the foam is isolated from the heat and sparks by a thermal barrier. 

One of the contractors visited asked that his workers be alone on the site. Another installed, at 

the entrance to the site, a sign announcing spraying work and recommending the wearing of 

protective equipment (respirator and goggles). 

The occupational health and safety practices documented in this section were observed on the 

sites visited and mainly involved hoisting equipment, fall protection, and the use of protective 

equipment (respiratory, skin and eye protection). 

5.3.1 Work zone approach equipment 

Here, the term "work zone approach equipment" refers to all equipment used to reach the higher 

surfaces to be sprayed, including motorized elevating platforms, tower scaffolding, platform 

scaffolding, stepladders and ladders. Spraying on interior structures was done from the ground 

and from a stepladder or mobile scaffolding, while that on exterior structures was done from the 

ground and a stepladder, mobile or stationary scaffolding, motorized platforms of the scissor 

type or with an articulated arm. The work zone approach equipment used during this study is 

listed in Table 2. One installer did not use any approach equipment. 

Table 2: Work zone approach equipment used on the sites visited 

Equipment used NS Used by Wearing of safety 

harness 

Tarpaulin 

shelter 

Stepladder 10 Installer only N/A N/A 

Motorized elevating 

platform, scissor type 

2 Installer and assistant No One situation

2 Installer only No One situation

Motorized elevating 

platform, articulated arm 

1 Installer only No No 

1 Installer and assistant Yes Yes 

FRACO® 2 Installer only No Yes 

Mobile scaffolding 1 Installer only Not obligatory < 3 m N/A 

Stationary scaffolding * 1 Installer only Not obligatory < 3 m N/A 

NS.: Number of situations or sites. N/A: Not applicable. *: Made of trestles and planks. 

FRACO®: A trademark for mast-climbing work platform as defined by the SCCI, article 1.1.14.2. 

The ladders used by the workers we met complied with the regulation for portable ladders: 

Portable ladders CAN3-Z11-M81, class I. However, the height selected was not always 

appropriate for the height of the structures to be insulated. The stepladder used was often too 
16 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

short. We also noticed that some of the workers climbed to the second last rung of the stepladder. 

Finally, the installer can extend his body beyond the reach of the stepladder, with a consequent 

risk of losing his balance and suffering a potential fall. 

Since the foam spraying operation is done on vertical surfaces at various heights from the 

ground, there is a risk of workers and tools falling. The installer and his assistant often used a 

motorized elevating platform of the scissor type or with an articulated arm for outdoor work that 

was done more than 3 metres from ground level. Very few workers we met had taken specific 

training in the use of such equipment. Finally, the wearing of a safety harness with an energy 

absorber is recommended by good practices for workers using any hoisting equipment for work 

above 3 metres from ground level. We noticed that safety harnesses were not always worn when 

such equipment was being used. 

In winter or in strong winds, the workers covered the motorized elevating platform and its 

articulated arm completely in plastic, making it dangerous in windy weather (see Figure 4). Any 

modification of such equipment should be duly approved as stipulated in regulation B354.2-01 

article 4.24 of the Canadian Standards Association. For further information on motorized 

elevating platforms, consult the “Guide de bonne pratiques : La pulvérisation de mousse de 

polyurethane” (Good practices guide: Polyurethane foam spraying) published jointly by the 

IRSST and ASP-construction.15

Figure 4: Non-compliant shelter on a motorized elevating platform 

5.3.2 Respiratory protection 

The installers wore respirators. Some wore an air-purifying respirator (APR) with chemical 

cartridges, powered or not, or with supplied air. However, several anomalies were observed. 

 

15 {On line} http://www.irsst.qc.ca/files/documents/PubIRSST/RG-623.pdf (August 2009). 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

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17

First, the air intake for the pump for the supplied air respirator was outside the truck, without 

taking into account the direction of the truck's exhaust gases, thus contaminating the air fed into 

the pump. Second, the air drawn in did not comply with the definition of respirable air (Grade D 

air); no analyses were done. Third, two workers used the same chemical cartridge respirator with 

half face mask without cleaning it or testing its fit. Generally, the respirators and their chemical 

cartridges were stored without protection in the truck box, where the barrels of resin and MDI 

were also stored. Finally, according to information from the workers, cartridges are changed 

when there is a perceptible odour. However, diisocyanates are odourless. But the VOCs (volatile 

organic compounds) from the resin smell of ether. The respirators noted during the study are 

listed in Table 3. 

Table 3: Respirators used 

Type of respirator Installer Assistant

N95 filter air purifying for aerosols, half face mask 2 

Chemical cartridge air purifying with half face mask 7 8 

Powered chemical cartridge filter air purifying with half face mask 1 0 

Powered chemical cartridge filter air purifying with full face mask 1 

Supplied air (unpurified) with half face mask 7 0 

Supplied air (unpurified) with full face mask 1 

No respirator 0 10 

During one survey, the occupational health and safety manager on site lent a cartridge respirator 

to a worker who had to work close to the spraying zone. This worker had never been trained in 

the wearing of a respirator and did not know how to put it on properly. 

5.3.3 Protective clothing 

The installers (or appliers) that did not wear a respirator with full face mask wore protective 

goggles. They also wore cotton gloves, with only one wearing nitrile gloves underneath the 

cotton ones. 

Whatever the season, the workers often wore their ordinary street clothes (jeans with a cotton 

sweatshirt with hood) without any protective coveralls. Their clothes were covered in foam and 

were not removed for meals or for transportation. Only one contractor insisted on the daily 

washing of clothing on his premises, even if the workers were wearing Tyvex® coveralls over 

their clothes. The protective clothing worn by the installers and assistants is listed in Table 4. 

Table 4: Protecting clothing 

Clothing Installers Assistants

Ordinary street clothes without protective clothing 7 13 

Cotton coveralls without incorporated hood 10 4 

Tyvex® coveralls with incorporated hood 2 1 
18 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

Two contractors required that Tyvex® coveralls with hoods be worn, with one contractor 

requiring them for the work team, and the other only for the installer. At the end of the work and 

for meals, the coveralls were removed. 

5.4 Ergonomic hazards 

In order to cover each of the surface strips to be insulated, repeated horizontal and vertical passes 

need to be done with the hand and wrist. The installer holds the gun (weighing about 1.4 kg. 

[about 3 lb]) and applies pressure with his index finger to produce a jet of foam. With his other 

hand, he pulls the feed hose (see Figure 5) and measures the thickness of the foam with the 

gauge. 

Figure 5: Spray gun and jet (Pierre Charbonneau, photographer) 

The installer stood upright on the ground or on a stepladder, on the platform of the hoisting 

equipment, or knelt or crouched with his back bent. During these movements, his arms were not 

supported and were often held above his shoulders. His body was often not centred on the 

stepladder rungs and he stood on the two last rungs.16 In winter, the hose became more rigid, 

further restricting the installer's movements when he tried to move the hose. Finally, the workers 

suffered from climatic constraints: heat in summer, particularly if they were wearing Tyvex® 

coveralls, and cold in winter. 

 

16 {On line} http://www.csst.qc.ca/portail/fr/publications/DC_400_1364_6.htm (March 2009). 

Masked window 

Gauge for 

measuring foam 

thickness 

Hand pulling 

the hose 

Width of strip 

Finger applying 

pressure 

Gun 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

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19

Finally, the main awkward positions observed were: 

• Repetitive movements of hand and wrist; 

• Raising the hand above the head, or the elbow 

above the shoulder; 

• Crouching position with or without back bent, 

or kneeling (see Figure 6). 

Figure 6: Crouching position (Pierre Charbonneau, photographer) 

5.5 Chemical hazards 

The chemical hazard described in this report refers exclusively to MDI exposure, although other 

solvents are used (see Appendix 2). The surface and thickness of the foam were factors 

influencing the duration of the spraying work, which varied between 37 and 48% of a full 

working day (8 hours). 

Ten teams of workers were followed for complete spraying jobs carried out for a full working 

day, representing 50% of the surveys. As mentioned above, the teams that were not followed for 

a complete spraying period had to go to another site where we were not allowed access. A brief 

description of the surveys carried out for each team of workers is summarized in Table 5.
20 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

Table 5: Brief description of surveys for each team of workers 

Survey Installer Assistant Comments

A 1 25 Full day of spraying work (outdoors) with frequent unplanned 

breaks, many workers on site, including welders near the spraying 

zone

B 2 26 Half day of spraying work (outdoors). 

C 3 27 Full day of spraying work (outdoors). 

D 4 * Half day of spraying work (indoors with several uncovered 

openings so conditions comparable to outdoor work) 

E 5 * Half day of spraying work (indoors) 

F 6 ** Full day of spraying work (indoors) on 3 floors of a residence, 

including crawl space 

G 7 ** Half day of spraying work (outdoors). The workers went to another

site (indoors) where the spraying zone was difficult to access for 

our sampling trains. 

H 8 ** Half day of sampling 

I 8 ** Day cut short due to climatic conditions for both teams

I 9 37 Day cut short due to climatic conditions for both teams 

J 12 30 Full day (indoors) belt sealing 

K 12 30 Full day (indoors) belt sealing 

L 13 ** Full day (outdoors). 

M 13 ** Half day (outdoors). 

N 14 32 Half day of sampling (indoors). The workers went to another site. 

O 15 ** Half day (outdoors) cut short due to climatic conditions. 

P 16 33 Half day of sampling (outdoors). The workers went to another site.

Q 17 39 Two sites (belt sealing). The workers carried out spraying 

18 38 operations, one in morning, one in afternoon. 

R 19 34 Half day (indoors). 

S 19 34 Half day (indoors). The two workers took turns spraying. 

20 35 

T 21 Full day, two sites (indoors), one spent sealing belts. 

*: No assistant. **: The assistant worked more than 10 m from the spraying zone. 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

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21

5.5.1 Analytical results and average MDI concentrations 

The analytical results for the stationary sampling are presented in Appendix 3. The flow rate of 

the pumps, measured with an electronic flow meter, did not vary more than 5% throughout the 

sampling. The number of samples, measurement ranges, and median per zone were as follows: 

A. Spraying zone:

• 47 average MDI concentrations (94 samples), for a range of monomer MDI concentrations 

from 11 to 591 μg/m3 (arithmetic mean: 114.8 μg/m3, and median: 54.8 μg/m3) and for the 

oligomers, from 3 to 330 μg/m3 (arithmetic mean: 59.3 μg/m3, and median: 20.1 μg/m3); 

B. Areas outside the spraying zone:

• Assistants: 24 samples for a range of monomer MDI concentrations from < 1 to 170 μg/m3 

(arithmetic mean: 67.9 μg/m3, and median: 45.5 μg/m3) and for oligomers from < 1 to 99 μg/m3 

(arithmetic mean: 33.0 μg/m3, and median: 24.5 μg/m3); 

• Other workers in the periphery: 29 samples for a range of HS monomer MDI vapour 

and aerosol concentrations from < 1 to 11 μg/m3 (median: 0.14 μg/m3); 

C. Post-spraying:

• 30 samples (22 on the floor where spraying had been done, and 8 on another floor) for a 

range of HS monomer MDI vapour and aerosol concentrations from < 0.01 to 2.4 μg/m3. 

Although this does not involve the workers' exposure, the equivalent of the daily average 

exposure value (DAEV) was calculated on the basis that there had not been exposure to MDI for 

the periods during which sampling did not take place. This calculation was done using equation 

1, cited in the RROHS. The average concentration was calculated using the same equation, but 

the denominator corresponded to the total duration of sampling for a spraying period that was the 

subject of the survey. This duration appears in the column "Duration" in Tables 6 and 7. 

DAEV = C1t1 + C2t2 + ...+ Cntn Equation 1 

t1 + t2 + ... + tn

Where: C = measured concentration of MDI for a given period; 

 t = MDI exposure time corresponding to the concentration measured; 

 1, 2, ..., n = Samples collected during the survey; 

 t1 + t2 + ... + tn = 8 hours or 480 minutes or the total duration of sampling. 

The average concentrations corresponding to a DAEV and the average concentrations of the 

samples in a spraying zone are listed by installer in Table 6. Those in the area outside of the 

spraying zone, corresponding to the zone where the assistants were working, are in Table 7. The 

lines in bold type correspond to the teams followed for a full day. It should be remembered that 

this was a complete spraying period for this team. 
22 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

Table 6: Inside the spraying zone : Average MDI concentrations per installer 

Installer

* Location Duration

(min)

DAEV for MDI (μg/m3) Average concentration of MDI 

samples (μg/m3)

Monomer Oligomers Monomer Oligomers

1 Outdoors 211 17.3 12.6 39.3 28.7

2 Outdoors 68 4.3 2.1 30.0 15.0

3 Outdoors 252 31.9 11.9 60.7 22.6

4 Indoors 176 14.0 6.4 38.0 17.6

5 Indoors 158 31.8 11.7 96.5 35.6

6 Indoors 216 48.1 22.8 106.8 50.6

7 Outdoors 95 14.0 7.8 70.8 39.2

8a Outdoors 161 3.7 1.4 11.0 4.1

8b Outdoors 175 7.8 5.6 21.3 15.3

9 Outdoors 211 36.8 18.7 83.6 42.5

12a Indoors 216 10.9 5.1 24.1 11.3

12b Indoors 226 13.3 6.3 28.2 13.4

13a Outdoors 257 20.3 5.4 38.0 10.1

13b Outdoors 125 19.6 10.4 75.1 40.1

14 Indoors 117 76.4 46.0 313.5 188.6

15 Outdoors 42 0.3 0.3 3.8 3.3

16 Outdoors 147 6.6 3.7 21.7 12.1

17 Indoors 115.5 11.5 5.2 47.9 21.7

18 Indoors 119 34.7 16.3 140.1 65.6

19a Indoors 243 243.2 134.9 480.5 266.5

19b ** Indoors 288 209.0 113.1 347.1 187.9

20 ** Indoors 54 13.1 7. 8 116.2 69.1

21 Indoors 141 38.9 14.6 132.3 49.6

Table 7: Outside the spraying zone : Average MDI concentrations per assistant 

Assistant

* Location Duration

(min)

DAEV MDI (μg/m3) Average concentration of MDI

samples (μg/m3)

Monomer Oligomers Monomer Oligomers

2 Outdoors 236 17.9 11.6 36.5 23.6

2 Outdoors 68 4.3 2.1 30.0 15.0 

2 Outdoors 190 13.0 5.2 50.0 20.0

3 Indoors 225 1.5 0.3 3.1 0.7

3 Indoors 151 4.0 1.8 12.7 5.6

3 Outdoors 147 6.6 3.7 21.7 12.1 

3 Indoors 246 51.6 29.5 100.7 57.5 

34b ** Indoors 289 93.7 52.9 155.6 87.9

35 ** Indoors 51 9.4 6.3 88.0 60.0

3 Indoors 143 30.2 9.9 101.5 33.1

3 Outdoors 211 36.8 18.7 83.6 42.5

* The number for an installer or an assistant may be repeated if he was present during the two surveys. 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

23

** The installer and the assistant took turns spraying on the two sites visited on that particular day.

Installers 4 and 5 worked alone. Assistants 28, 29, 31 and 32 worked at a distance from the 

spraying zone. The workers in one team shared the spraying period: Installer 19b became 

assistant 35, and installer 20 became assistant 34b. 

The average concentrations by zone corresponding to that of the installer and his assistant are 

summarized in Table 8. The averages of the concentrations for indoor work by zone are listed in 

Table 9. 

Table 8: Average MDI concentrations by zone by location/season 

Location of work: Indoors Outdoors

Season: Winter Summer Winter Summer

Zone Aerosols + vapours Average MDI concentration (μg/m3)

Spraying

(installer)

monomer 93.0 206.7 43.0 48.2 

oligomers 50.7 106.1 20.0 26.3 

Work zone

assistant

monomer 12.5 90.8 53.6 41.8 

oligomers 5.5 45.7 28.6 25.1 

Table 9: Average MDI concentrations by zone for indoor work 

Zone

MDI Average MDI concentration (μg/m3)

Aerosols + vapours Insulation Sealing

Spraying

(installer)

monomer 288.7 83.3 

oligomers 151.1 43.1 

Work zone

assistant

monomer 135.6 27.3 

oligomers 71.8 10.5 

The average MDI concentrations in the area outside the spraying zone (work zone for workers in 

other specialties) by floor with regard to the work are indicated in Table 10. 

Table 10: Average MDI concentrations in the area outside the spraying zone 

MDI Average MDI concentration (μg/m3)

Same floor Another floor

Aerosols + vapours: monomer 20.0 - - 

Aerosols + vapours: oligomers 10.7 - - 

High Sensitivity monomer vapours 1.9 2.0 

The average HS monomer MDI vapour concentrations for the post-spraying samples are listed in 

Table 11 and illustrated in Figure 7. 

Table 11: Average monomer MDI concentrations: post-spraying by floor 

Post-spraying 

sampling

Average MDI concentration HS vapours (μg/m3)

Floor where spraying took place Another floor

30 minutes 0.35 μg/m3 0.30 μg/m3 

60 minutes 0.08 μg/m3 0.95 μg/m3 

120 minutes 0.03 μg/m3 0.02 μg/m3 
24 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

HS MDI vapours - Post spraying

0

0,2

0,4

0,6

0,8

1

0 30 60 90 120 150

Minute

Concentration (μg/m3)

Floor where spraying Another floor

Figure 7: Average of the monomer MDI concentrations in post-spraying samples 

The target parameters (DAEV and average concentrations of monomer and oligomers MDI) 

were analyzed statistically according to determining factors that could modify MDI exposure in 

the spraying zone and in the area where the assistant works. In order to do this, we checked 

whether the groups were similar (SEG): 

I. If a distribution of more than five data is lognormal and has a geometric standard 

deviation (GSD) less than 3,17 the group would be relatively similar for this determining 

factor. 

II. If the 95th percentile of the distribution is greater than the PEV of MDI, there would be a 

risk of exposure, with a certain fraction exceeding the PEV, for a probability of around 

5%. 

Certain determining factor distributions with fewer than five data are not mentioned in the tables 

in Appendix 4. 

5.5.2 Other exposure risks 

According to the safety data sheets, there were other chemical substances present (see Appendix 

2) that were not sampled. The workers were not wearing gloves when they used these products, 

some of which are classified as having dermal effects. 

It is possible that liquid containing MDI or other solvents could splash into the eyes or onto the 

skin, particularly during transfer of the aspiration system from an empty barrel to a full one (a 

task observed once), when the residual solution is being emptied from the barrel, etc. One team 

had a portable eye-wash device. 

 

17 IHSTAT uses a GSD below 2.5. 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

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6. DISCUSSION 

The study covers a range of sites (see section 5.1), each different from the others, mainly with 

respect to the work carried out (insulation of walls or sealing of belts), its location (indoors or 

outdoors), the season in which it was done (summer or winter), the surface area of the spraying 

floor, and work organization (installer working alone or installer plus assistant). 

Furthermore, the spraying technique used by the installers depended on their professional 

experience. Some had attended the training program prescribed by CUFCA, while others will 

attend it as soon as they have worked the required number of hours. These variables, specific to 

the site and work teams, affect the results of the study, limiting their scope. 

The results in this report are representative of the conditions existing on the survey days on the 

sites visited according to the work performed. 

6.1 Work organization 

In the course of a single day, one team of workers could work on more than one site. There is 

then a longer transport time (from one site to another). The work to be carried out may differ 

from one site to another: insulation of exterior walls, interior walls (basements or on the upper 

floor), or sealing of belts. 

6.2 Health and safety practices 

If workers need to access enclosed or confined spaces, they must have the recommended training 

on the hazards and risks and must also have the appropriate equipment with them at all times to 

ensure that they can exit in case of an emergency. It should be remembered that, in the case 

encountered, the workers had not received this training. 

6.2.1 Hoisting equipment 

By using a stepladder not sufficiently high and standing on the top rung, the worker is in an 

unstable position and risks losing his balance. Figure 8 shows the position of the body on a rung 

of a stepladder. 

Figure 8: Position of worker on a rung of a stepladder (Pierre Charbonneau, 

photographer) 
26 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

Even though there is no strict legal obligation, good occupational health and safety practices

recommend the wearing of a safety harness to protect against falls from heights of over 3 metres 

with any motorized elevating platform (scissor-type, articulated arm) since its guard-rail does not 

protect the worker from such things as whiplash resulting from mechanical failure, collision, etc. 

The fact that the workers had not been trained to work on this hoisting equipment may explain 

why this rule of good practice was not observed. 

The wind can render a plastic shelter unstable (see Figure 4) when installed on hoisting 

equipment. The plastic sheeting should be wound around the horizontal and vertical members 

and railings of the equipment (Figure 9) since it is there to protect the equipment and not to allow 

work to continue despite unfavourable weather conditions. 

Figure 9: Protection of vertical members and cross members of hoisting equipment 

6.2.2 Protective equipment 

Theoretically, no worker should be present in the spraying zone unless he is wearing appropriate 

personal protective equipment, including a properly fitting respirator supplying fresh air. 

According to Table 3, none of the assistants we met had worn a respirator when they were in the 

spraying zone, in particular assistants 26 and 33 who were in the hoisting equipment. 

Specific respirator training (use, maintenance, tight fit, etc.) should be given so that workers 

know how to wear a respirator correctly. 

Anyone close to the spraying zone should wear the appropriate protective equipment. The work 

should be posted on a sign at the entrance to the site. It should also be mentioned that no worker 

may enter the spraying zone without personal protective equipment as specified by the 

regulations.18

 

18 The CAN/ULC S705.2 standard establishes the requirements for environmental conditions and other 

documentation relevant to spraying operations. 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

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27

Considering the state of knowledge on dermal exposure to diisocyanates, it would be advisable that 

protective clothing made of appropriate materials be worn in order to protect workers in this sector. 

The Service du repertoire toxicologique (REPTOX) of the CSST19 recommends the wearing of 

polyethylene/vinyl alcohol and ethylene/polyethylene gloves (PE/EVAL/PE) and impervious 

protective clothing made of Barricade® covering the whole body. 

In addition to the CSST, other organizations suggest occupational health and safety practices for 

the spraying of isocyanate-based products. For example, Work Safe Alberta20 recommends the 

wearing of a respirator with a full face mask or airtight goggles/mask to protect the eyes, coveralls 

to protect the arms and legs, and resistant gloves, without specifying the material. 

6.3 Ergonomic hazards 

The adoption of a rigid posture in order to remain stable on a stepladder can cause significant 

muscle strain in the back, particularly if the worker is on the next to last step. Access to this level 

is not recommended. Moreover, the narrow support surface does not allow the installer to pivot 

his feet. This means that he can only turn his body, with the risk of losing his balance. 

6.4 Chemical hazards 

Since the installers wore respirators and the sampling trains used included an impinger containing a 

collecting solution, stationary sampling was done. It should be remembered that the results 

obtained represent contamination of the work areas and not worker exposure. 

6.4.1 MDI concentration in the spraying zone 

The average of the MDI concentrations in the spraying zone, taking all categories of sites 

together, exceeds the permissible exposure value in Québec by about 2.3 times, and in the area 

outside the spraying zone (where the assistants work), by about 1.3 times. As an example, 

installer 14 was in the spraying zone on the first site we visited. There was an average MDI 

concentration of 313.5 μg/m3 in this zone, more than six times the PEV, and a DAEV of 76.4 

μg/m3. Whatever the duration of spraying on the second site, the PEV was exceeded on the first 

site by estimating a zero concentration on the second site. 

Next, let us examine the results for the installer-assistant teams that took turns in the spraying 

operation (Table 12). The DAEV corresponding to the work zone of installer 19b and assistant 

35 was 217.6 μg/m3, while for the work zone of installer 20 and assistant 34b, it was 106.7 

μg/m3. 

Table 12: Average concentrations of monomer MDI by task 

Team Duration

(min)

MDI concentration 

during spraying

Duration

(min)

MDI concentration 

during assistant's tasks

DAEV

(μg/m3)

19b-35 288 347.1 μg/m3 51 88.0 μg/m3 217.6 

20-34b 54 116.2 μg/m3 289 155.6 μg/m3 106.7 

 

19 {On line} 

{http://www.reptox.csst.qc.ca/Produit.asp?no_produit=12393&nom=Diisocyanate%2D4%2C4%27+de+diph%E9ny

lm%E9thane+%28MDI%29} (April 2008). 20 {On line} http://employment.alberta.ca/documents/WHS/WHS-PUB_ch005.pdf (December 2008). 
28 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

The period during which installer 19b carried out the tasks of an assistant was shorter 

(51 minutes) than that in which he was spraying (288 minutes). During execution of the assistant's 

tasks, the workers did not wear respiratory protective equipment and the monomer MDI 

concentrations were 1.7 and 3.1 times above the PEV. The assistant must wear a respirator. 

As mentioned above, the assistants were sometimes in the spraying zone. For example, assistant 

37 was present with installer 9 on the platform where a shelter had been installed (Figure 4). The 

average MDI concentration under this shelter was 83.64 μg/m3 (1.6 times the PEV). Frequently, 

the assistant present on hoisting equipment did not wear any respirator, while our results show 

high concentrations of MDI. 

In the case of installer 16 (who was wearing a respirator) and his assistant 33 (who was not 

wearing a respirator), their calculated DAEV took into account only the work carried out on the 

first site that they visited on the day of our survey. 

The MDI concentrations for the work performed in summer were higher than those observed in 

winter (Table 8), and those for insulation work performed indoors would correspond, for the 

spraying zone, to 5.7 times the PEV, and for the assistant's area, to 2.7 times the PEV (Table 9). 

Hypotheses can be made regarding the surface of the work floor, the thickness and quantity of 

foam sprayed, or the installer's experience. 

The previously mentioned studies obtained results varying from 17 to 400 μg/m3 for the installer 

(0.3 to 7.8 times the PEV in Québec). Our stationary sampling results in the spraying zone varied 

from 11 to 591 μg/m3 (0.2 to 11.6 times this PEV). They are comparable to those reported in the 

literature. 

In conclusion, the concentrations in the spraying zone for indoor work were the highest, 

particularly in summer, while those for outdoor work were equivalent in both summer and winter. 

6.4.2 MDI concentration outside the spraying zone 

The average of the concentrations in the assistant's work area is about 1.7 times lower than that in 

the spraying zone (see Appendix 3). The previously mentioned studies had obtained results of 10 

to 310 μg/m3 in the assistant's work area (0.2 to 6.1 times this PEV). Our results for the 

assistant's area were from 2 to 170 μg/m3 (0.04 to 3.3 times the same PEV), and therefore lower than 

those reported in those studies. 

In the zones occupied by workers of other trades, the averages of the analytical results for HS 

MDI monomer vapours were low: about 3.8% of the PEV (Table 10). In these areas, which were 

rather distant from the spraying, the probable presence of aerosols was low, unless it was 

accidental spraying off target. The absence of workers from other trades reduced their risk of MDI 

exposure as prescribed in the RROHS, which mentions reducing such exposure to a minimum. It 

is therefore advisable that the employment contract mention that no worker can be present in the 

spraying zone unless he is wearing personal protective equipment. 

In conclusion, the assistants outside the spraying zone came into contact with MDI aerosols to a 

lesser degree. Workers from other trades located outside the spraying zone (> 10 m) came into 

contact with low concentrations of monomer MDI vapour (about 4% of the PEV). 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

29

6.4.3 Post-spraying MDI concentration 

The HS MDI vapour results from the post-spraying samples (Table 11) varied from the analytical 

limit of quantification to 2.4 μg/m3. This last result was obtained in the first hour following the 

end of spraying, while the result for the next hour was 0.013 μg/m3. There would have been an 

average concentration of 0.029 μg/m3 two hours after the end of spraying (≤ 0.01% of the PEV). 

The highest result reported in the Lesage et al. (2007) study was 19 μg/m3 in the first 15 minutes 

following the end of spraying. However, the very great majority of the post-spraying results 

(except for four) in that study were below the 0.036 μg analytical limit of quantification. In fact, 

all of the results after one hour were below this limit. The difference between the results in that 

study and ours lies mainly in the limit of quantification of the analytical methods (see Table 2). In 

fact, the analytical limit of quantification for the monomer MDI vapour analyzed according to the 

high sensitivity IRSST method was 0.00075 μg, while that in the Lesage et al. (2007) study was 

0.036 μg for the monomer. 

The suggested good practices following the situations observed during the study are summarized 

in Table 13. 

Table 13: Good practices recommended and poor practices observed 

Regulation/standard/recommendation/good practices Poor practices observed Good practices 

• Winding the plastic sheeting 

around the hoisting equipment’s 

members 

9 Producing temporary shelters on 

hoisting equipment 

• Protection of respirator in a 

hermetically sealed bag 

• Seal (fit) test 

9 Respirator and cartridges incorrectly 

stored 

9 No fit test 

• To be stipulated in employment 

contract: People other than those 

involved in spraying are prohibited 

9 Presence of workers from other 

specialties 

• Wearing of safety harness to 

protect from falls from heights and 

with energy absorber if falls from 

heights greater than 3 metres are 

possible, no matter what other 

equipment is used 

9 Hardly any or no harnesses worn 

• Height of stepladder appropriate 

for height of work 

http://www.csst.qc.ca/portail/fr/pu

blications/DC_400_1364_6.htm 

9 Height of stepladders inappropriate 

for height of work 

9 Standing on second rung from top 

9 Body weight not centered on step 

CSST, Service du 

répertoire 

toxicologique 

(REPTOX) 

• Wearing of PE/EVAL/PE gloves 

and leakproof protective clothing 

made of Barricade® covering the 

whole body 

9 No nitrile gloves worn under cotton 

gloves 

9 Tyvex® coveralls hardly worn 

CSST-IRSST, Guide 

pratique de protection 

respiratoire

• Supplied air respirators 

• If coveralls with hood are not 

worn, then wear full hood and 

supplied air respirator 

9 Supplied air respirators hardly used 

by installers 
30 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

Regulation/standard/recommendation/good practices Poor practices observed Standard CAN/ULC-S705.2 of Underwriters’ Laboratories of Canada (ULC) 

• Wearing of gloves, coveralls with 

hood, goggles or protective mask, 

safety shoes, safety helmet 

9 No gloves made of nitrile or other 

appropriate material 

9 No Tyvex® coveralls with hood 

9 Frequently no safety helmet 

• Training program for installers 9 Before training, a number of hours of 

on-the-job spraying work are 

required 

• Protect the foam from heat and 

sparks with a thermal barrier if 

there are ignition sources close to 

the spraying zone 

9 No protection 

• Sign announcing spraying work 9 No signs 

9 Presence of workers 

• No workers must be present in the 

spraying zone without respirators 

and goggles 

9 Presence of workers in spraying zone 

without protective equipment 

RROHS article 264 

SCCI article 2.9.1 

CAN/CSA Z259.10-

M90 

• Wearing of safety harness to 

protect against falls from heights, 

with energy absorber 

9 Not respected 

9 No training in the use of hoisting 

equipment 

RROHS article 48 

Standard 

CAN3Z180.1-M85 

• Air tested once a year 9 Air not compliant (not tested) 

9 Air potentially contaminated by 

exhaust gases 

RROHS articles 1, 297 

to 302, 306 

SCCI article 1.1.17.1 

• Enclosed or confined spaces - 

training 

9 No training in hazards and risks, 

measurement of concentrations, etc. 

9 Not included in the training program 

for installers 

Polyurethane MDI 

Handbook21 • No eating or drinking in places 

where MDI is handled or stored 

9 Not respected 

6.4.4 Statistical analysis 

According to the statistical analysis (Appendix 4), there is a risk of MDI exposure for the 

installers (or appliers) during indoor work in summer. Summer outdoor work for assistants 

appears to present a lower risk of MDI monomer exposure if it is done outside the spraying zone. 

There is considerable variation in the majority of the distributions of most determining factors for 

these two parameters since: 

1) The DAEV did not always correspond to a complete spraying period. Some teams went 

to another site where no sampling was carried out. 

2) The DAEV and the average concentrations for a survey varied with the installer's skill 

and experience, from one worker to another for the same task, the same location and the 

same season. 

 

21 {On line}. {http://www2.basf.us/urethanechemicals/Specialty_Systems/pdfs/2000mdihandbook.pdf} (November 

2008). 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

31

3) The DAEV and average concentrations for a survey corresponded to different levels of 

productivity, depending on the site and the work, the weather conditions, and the 

volume of the building (interiors). The work was frequently different from one day to 

another, varying mainly according to the customer's particular requirements. 

4) The DAEV and average concentrations for the assistant's tasks reflected the variability 

in their professional practices. Some entered and stayed in the spraying zone while 

others did not. 

5) The DAEV and average concentrations for a survey varied from one installer to another, 

depending on their skill and professional experience. 

As mentioned previously, only the monomer form of isocyanates is regulated in the RROHS, 

although oligomers are scientifically recognized as being toxic (section 2, Issues and State of 

Knowledge). The United Kingdom, through the HSE, is a country that has a reference value 

reflecting all of the isocyanate functions and taking into account the scientific data on the 

toxicity of oligomers. It would be appropriate for the Québec PEV to be reconsidered in order to 

take all of the isocyanate functions into account. 

6.5 Other risks of exposure 

Since several of the products used have effects resulting from skin contact, it is recommended 

that gloves be worn because skin irritation and inflammation may result from such contact, 

depending on the quantities and frequency of use. For the case of splashing, workers should 

have a kit containing a portable eye-wash device and bottled water to rinse their 

hands and faces. 

6.6 Recommendations 

Different avenues may lead to the control of MDI exposure risks, in particular by informing 

workers about: 

• the chemical hazards in handling isocyanates (occupational asthma and contact dermatitis) 

• the wearing of supplied air respirators by installers and assistants present in the spraying 

zone 

• the safe storage of cartridges and respirators 

• the wearing of appropriate personal protective equipment (nitrile or PE/EVAL/PE gloves, 

and coveralls with hoods made of Tyvex® or Barricade®) 

• the hazards and risks related to enclosed or confined spaces (qualified workers, 

environmental monitoring, supervisor, etc.) 

• the wearing of gloves made of materials appropriate for the solvents present in the product 

being used (consultation of safety data sheets) 

• the wearing of safety harnesses to protect against falls from heights during the use of 

hoisting equipment. 
32 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

This information should, among other things, be distributed in the training program and be the 

subject of periodic refresher training. 

In summary, one of the particular characteristics of this study was the variety of work situations 

observed during polyurethane foam spraying. The sources of uncertainty in the reported results 

are mainly related to environmental fluctuations, which are greater than those related to the 

sampling and laboratory analyses. The latter are minor and even negligible compared to the 

others. The height of the spraying strips varied continually, while that of the sampling trains 

remained fixed at approximately 1.5 m from the ground (equivalent to the installer's breathing 

zone during the spraying of the middle sections). In fact, the installer sprayed the upper, middle 

and lower parts of each strip. Furthermore, the trains were positioned on each side of the installer 

so as not to hinder the work or the movement of the worker and his equipment. These 

movements, in relation to the positioning of the trains, affected the concentrations obtained in 

each of the trains surrounding the spraying zone. Also, the environmental fluctuations depended 

on the type of site (commercial or residential) and on its surface area, features of the work 

(insulation of walls, sealing), on its location, the season, the work method, and the installer’s 

experience. 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

33

7. CONCLUSION 

The results of this study relate to the workers' immediate environment and not their actual 

personal exposure. The work zones of workers spraying polyurethane foam, particularly in the 

spraying zone, were exposed to monomer MDI that could exceed the Québec PEV, and to 

oligomers. In view of these results, the workers must wear supplied air respirators. The air fed 

into the device should meet the requirement of the standards (Grade D air). The workers must 

also protect themselves against the possibility of skin contact by wearing gloves and coveralls 

with hoods, even though there is no consensus in the literature on sensitization through skin 

exposure to MDI. 

Workers close to the spraying zone are at risk of exposure to MDI vapours. It would therefore be 

advisable to avoid any work close to this zone. A sign must be posted announcing the work and 

the requirement to wear protective equipment. 

Post-spraying samples have shown that residual monomer MDI vapours are present for 

approximately two hours. However, their concentrations are low (≤ 0.01% of PEV). 

In addition to the chemical hazards, the study has pinpointed the health and safety practices to be 

changed and the relative weaknesses of this aspect of the work in the installers' training program. 

The organizations providing training to foam installers should more rigorously integrate all 

aspects of occupational health and safety, particularly for the construction site health and safety 

course, for all construction site workers. We reiterate that motorized elevating platforms must be 

used with safety harnesses to protect against falls from heights, that respiratory and skin 

protection must be used, and that other workers should not be permitted entry into the spraying 

zone. Based on the results of this study, a good practices guide has been produced jointly with 

ASP- Construction.22

 

22 {On line} http://www.asp-construction.org/utilisateur/documents/prevenir-aussi/prevenir_printemps2009.pdf

(April 2009). 

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

35

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{January 2009}. 

ALBERTA HUMAN RESOURCES AND EMPLOYMANT, The People & Workplace 

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(November 2008). 

BERNSTEIN, I Leonard ; Moira Chan-Yeung, Jean-Luc Malo and David I Bernstein. In Asthma 

in the Workplace, New York, Éd. Taylor&Francis Group, 2006, 874 p. 

BERNSTEIN, JA. « Overview of diisocyanate occupational asthma » Toxicology vol. 111, 1996 

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BILAN, R; WO Haflidson and DJ McVittie. « Assessment of Isocyanate Exposure during the 

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BOUCHARD, Pierre and al. « Les échafaudages de types mobiles: Guide » DC 200-1704 (02-

04) CSST, Montréal 30 p. {On line}. {http://www.csst.qc.ca/NR/rdonlyres/4606171D-DE5D41A1-8287-310AC146AC62/2892/DC_200_1704_4.pdf} (April 2008). 

CREELY, Karen S; Graeme W Hughson; John Cocker and Kate Jones. « Assessing Isocyanate 

Exposures in Polyurethane Industry Sectors Using Biological and Air Monitoring Methods », 

American Occupational Hygiene, vol. 50 n° 6, May 2006, p. 609-621. 

CRESPO, J. and J Galan. « Exposure to MDI during the Process of Insulating Building with 

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p. 415-419. 

DHIMITER Bello; Christina A. Herrick; Thomas J. Smith; Susan R. Woskie; Robert P. 

Streicher; Mark R. Cullen; Youcheng Liu and Carrie A. Redlich « Skin Exposure to Isocyanates: 

Reasons for Concern ». Environmental Health Perspectives, March 2007, vol 115, no 3 p. 328-

335. 
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GOUVERNMENT OF QUÉBEC. Safety Code for the Construction Industry (SCCI). Éditeur 

officiel du Québec, February 2008 258 p. (S-2.1, r.6) {On line}. 

{http://www2.publicationsduquebec.gouv.qc.ca/dynamicSearch/telecharge.php?type=2&file=%2

F%2FS_2_1%2FS2_1R6.htm} (November 2008) 

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respecting occupational health and safety (RROHS), Éditeur officiel du Québec, February 2008, 

220 p. (S-2.1, r19-01). {On line}. 

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F%2FS_2_1%2FS2_1R19_01.htm} (November 2008). 

HEALTH AND SAFETY EXECUTIVE (HSE). Method for the Determination of Hazardous 

Substances. Organic isocyanates in air. London: HSE; 1999 {On line}. 

{http://www.hse.gov.uk/pubns/mdhs/pdfs/mdhs25-3.pdf} (April 2008). 

HERRICK Christina A; Lan Xu; Adam V. Wisnewski; Jyoti Das; Carrie A. Redlich and Kim 

Bottomly.« A novel mouse model of diisocyanate-induced asthma showing allergic-type 

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immunology 2002, vol. 109, no

5, p. 873-878.

HOSEIN, HR. and S Farkas. « Risk associated with the spray application of polyurethane 

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KAROL, MH; BA Haulh; EJ Riley and CM Magreni; « Dermal contact with toluene 

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Applied Pharmacology vol 58 no 2, April 1981, p. 221-230. 

UNDERWRITERS’ LABORATORIES OF CANADA ULC. Standard for thermal insulation – 

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2nd edition, February 2005. 

LARA, Jaime and Mireille Venne. « Guide pratique de protection respiratoire ». CSST and 

IRSST, 2e Edition 2003, p. 56 {On line}. 

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LESAGE, Jacques; Jennifer Stanley; William J Karoly and Fran W Lichtenberg. « Airbone 

Methylene Diphenyl Diisocianate (MDI) Concentrations Associated with the Application of 

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Environmental Hygiene, vol. 4, February 2007, p. 145-155. 

LESAGE, Jacques and Claude Ostiguy. « Les outils d'évaluation des isocyanates », Programme 

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Montréal, IRSST, September 2000. {On line}. 

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(April 2008). 

LESAGE, Jacques and Claude Ostiguy. « Les isocyanates en milieu de travail : aspect 

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MARLAIR G. « Rubrique 1158 : MDI Di-isocyanate de diphényl méthane » INERIS DRA 

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January 2002 p 21. {On line} www.ineris.fr/index.php?module=doc&action=getFile&id=2274

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NADEAU, Daniel. « Les isocyanates et leurs effets sur la santé », Programme provincial sur les 

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2008). 

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RESEARCH AND DEVELOPMENT DEPARTMENT, CONSTRUCTION SAFETY 

ASSOCIATION OF ONTARIO. « Assessment of isocyanate exposure during the spray 

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Cassinelli and Paula Fey O’Connor, « Determination of Airborne Isocyanate Exposure: 

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VANOIRBEEK Jeroen AJ; Maciej Tarkowski; Jan L. Ceuppens; Erik K. Verbeken; Benoit 

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May 2004, vol 80, p. 310-321. 

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

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APPENDIX 1: LIST OF POINTS RELATING TO WORK METHODS 

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

41

Polyurethane foam spraying: Work methods 

Site: New construction ⁭ Renovation: ⁭ Year of construction ________________ 

Type of building: Single floor residence: ⁭ Dimension: ________________________ 

 Cottage: ⁭ Dimension: ________________________ 

 Commercial: ⁭ Dimension: ________________________ 

How many workers carry out spraying? ________ Installer _____________ Assistant 

___________ 

Tasks performed by assistant: Preparation (masking) ⁭ Cleaning ⁭ Spraying ⁭

_______________________________________________________________________________________ 

_______________________________________________________________________________________ 

_______________________________________________________________________________________ 

_______________________________________________________________________________________ 

Presence of other workers on the site:_________________________________________________________

Presence of other people in the residence: ____________________________________________________ 

Truck: Condition of site: Cluttered Yes ⁭ No ⁭ _________________________________ 

_______________________________________________________________________________________ 

Condition of equipment: Clean Yes ⁭ No ⁭ Gun: _____________________________ 

Work Indoors ⁭ Outdoors ⁭

Basement: ⁭ Floor: _____________ 

Height of ceiling *: __________________________ 

Access by a door: ⁭ Opening *: ⁭

By a ladder* ⁭ Stepladder ⁭

Condition of site______________________________ 

___________________________________________ 

___________________________________________ 

Number of outside doors:_____________________ 

Number of windows or wall openings and condition: 

North ⁭ ______ : Masked ⁭ Closed ⁭

South ⁭ ______ : Masked ⁭ Closed ⁭

West ⁭ ______ : Masked ⁭ Closed ⁭

East ⁭ ______ : Masked ⁭ Closed ⁭

* NB: This might be an enclosed or confined space. 

See below. 

Ground level: ⁭ Height_____________ 

Height of structure:__________________________ 

Condition of ground: __________________________ 

Condition of walls: ____________________________

Condition of site: ____________________________ 

___________________________________________ 

___________________________________________ 

Number of outside doors:_____________________ 

Number of windows or wall openings and condition: 

North ⁭ ______ : Masked ⁭ Closed ⁭

South ⁭ ______ : Masked ⁭ Closed ⁭

West ⁭ ______ : Masked ⁭ Closed ⁭

East ⁭ ______ : Masked ⁭ Closed ⁭
42 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

Polyurethane foam spraying: Work methods 

Spraying performed from: Ground ⁭ Stepladder ⁭ Ladder ⁭

Hydraulic hoisting equipment used:

Scissor-type: ⁭ Height ____________________ Articulated arm: ⁭ Height ____________________ 

Platform: ⁭ Height ____________________ Other: _________________________________________ 

_____________________________________________________________________________________ 

Thickness sprayed: _______________________ 

Number of coats: ________________________ 

(2 in. < coats > 1⁄2 in.) 

Safety to be promoted when using hydraulic 

equipment: __________________________________ 

____________________________________________

Gun cleaning: Product used: __________________________ Duration of cleaning: _______________ 

Delimitation of exclusion zone: Yes ⁭ No ⁭

Sign announcing spraying work: Yes ⁭ No ⁭

Message: _______________________________________________________________________________ 

_______________________________________________________________________________________ 

If an enclosed or confined space: 

Explain the configuration of this space and its features: 

______________________________________________ 

Partially closed ⁭ Completely closed ⁭

Access by ladder ⁭ Stepladder ⁭ Other _____________________________________ 

Design or construction ____________________________________________________________________ 

_______________________________________________________________________________________ 

_______________________________________________________________________________________ 

Ventilation: natural ⁭ mechanical ⁭ _______________________________________ 

Contaminants emitted or contained: _________________________________________________________ 

_______________________________________________________________________________________ 

Are the workers informed that it is a confined space? Yes ⁭ No ⁭

If so, what are their instructions or procedures? ____________________________________________ 

_______________________________________________________________________________________ 

_______________________________________________________________________________________ 

_______________________________________________________________________________________ 

_______________________________________________________________________________________ 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

43

Polyurethane foam spraying: Work methods 

Ergonomics: Weight of gun: ___________________________ 

Awkward postures: Working ... 

1. with hands above head ______________________________________________________________ 

2. with hands repeatedly raised above head ___________________________________________________ 

3. with bent elbows ______________________________________________________________________ 

4. with back bent more than 45° ___________________________________________________________ 

5. with bent neck _______________________________________________________________________ 

6. with bent wrists ______________________twisted wrists _____________________________________ 

7. crouching ____________________________________________________________________________ 

Tasks performed by other workers present:

Welding: Yes ⁭ No ⁭ Type of welding ________________________________________ 

Distance from the spraying zone: __________________ 

Excavation and formwork: Yes ⁭ No ⁭ Roofing: Yes ⁭ No ⁭

Electrician: Yes ⁭ No ⁭ Carpenter: Yes ⁭ No ⁭

Plumber: Yes ⁭ No ⁭ Installation of ventilation: Yes ⁭ No ⁭

Use of propane-powered equipment: 

_____________________________________________________________ 

Describe the work performed by these workers and at what distance from the spraying zone: 

________________________________________________________________________________________ 

________________________________________________________________________________________ 

________________________________________________________________________________________ 

Installer’s protective equipment: 

Respirator: Yes ⁭ No ⁭

Full face mask ⁭ Half mask ⁭

Supplied air: filtered (pump at belt): 

Pump ⁭ Compressor ⁭

Filter unit (respirable air) Yes ⁭ No ⁭

Near gas emission (truck): ______________________ 

Cartridges_________________________________ 

Type ______________________________________ 

How often changed: __________________________

Assistant’s protective equipment: 

Respirator: Yes ⁭ No ⁭

Full face mask ⁭ Half mask ⁭

Supplied air: filtered (pump at belt): 

Pump ⁭ Compressor ⁭

Filter unit (respirable air) Yes ⁭ No ⁭

Near gas emission (truck): ______________________ 

Cartridges_________________________________ 

Type ______________________________________ 

How often changed: __________________________
44 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

Polyurethane foam spraying: Work methods 

Storage of respirator when not used _______________

Respirator training: Yes ⁭ No ⁭

Received by: Respirator representative ⁭

 Firm ⁭

Someone from company ⁭ Other ⁭

Falls from heights: Harness: Yes ⁭ No ⁭

Explain ____________________________________ 

___________________________________________ 

Clothing: Coveralls ⁭ Street clothes ⁭

Material: Tyvex® ⁭ Other ________________ 

Gloves: Yes ⁭ No ⁭

Material ___________________________________ 

Appearance of clothing: _______________________ 

Maintenance: in company ⁭ at home ⁭

Safety helmet: Yes ⁭ No ⁭__________ 

Goggles: Yes ⁭ No ⁭ _________ 

Safety shoes: Yes ⁭ No ⁭

Storage of respirator when not used 

_______________ 

Respirator training: Yes ⁭ No ⁭

Received by: Respirator representative ⁭

 Firm ⁭

Someone from company ⁭ Other ⁭

Falls from heights: Harness: Yes ⁭ No ⁭

Explain ____________________________________ 

___________________________________________ 

Clothing: Coveralls ⁭ Street clothes ⁭

Material: Tyvex® ⁭ Other ________________ 

Gloves: Yes ⁭ No ⁭

Material ___________________________________ 

Appearance of clothing: _______________________ 

Maintenance: in company ⁭ at home ⁭

Safety helmet: Yes ⁭ No ⁭__________ 

Goggles: Yes ⁭ No ⁭ _________ 

Safety shoes: Yes ⁭ No ⁭

Spraying season: 

Summer ⁭ Winter ⁭

Ambient temp: _________°C Humidity: ____________ Direction of air currents: _________________ 

Velocity (<24 Km/h): ________________________ 

Doors and windows opened during work: ______________________________________________________ 

Type of shelter: ________________________________ Propane heating: ____________________________ 

Ventilation:_____________________________________________________________________________

Sanitary installations: Portable toilet: Yes ⁭ No ⁭ Eye wash: Yes ⁭ No ⁭

Comments: ______________________________________________________________________________ 

________________________________________________________________________________________ 

________________________________________________________________________________________ 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

45

APPENDIX 2: LIST OF PRODUCTS USED

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

47

Product Substance23 CAS#24

 4,4’-Diphenylmethane diisocyanate (MDI) 101-68-8 

Polymeric MDI (PMDI) 9016-87-9 

Polyol (proportions

vary according to 

version, regular or 

winter)

 25723-16-4 

Dichloroethylene (two isomers) 156-60-5 

1,4-Dioxane 123-91-1 

1,1-Dichloro-1-fluoroethane 1717-00-6 

1,1,2-Trichloro-1,2,2-trifloroethane 76-13-1 

N,N-Dimethyl-2-aminoethanol 108-01-0 

1,1-Chloro-1,1-difluoroethane 75-68-3 

Diethylamine 109-89-7 

1,3-Dioxane 505-22-60 

Traces of xylenes 1330-20-7 

Foaming agent 1,1,1,2,2-Pentafluoropropane (HFC 245FA). 460-73-1 

 Gun cleaning solvent Dipropylene glycol monomethyl ether 34590-94-8 

Adhesive (contact glue) Hexane 110-54-3 

Acetone 67-64-1 

Toluene 108-88-3 

 

23 These substances are mentioned in the product safety data sheets. This list does not contain all the substances 

because some may only be in trace amounts in the mixture. 24 CAS#: This is the registration number for a chemical substance in the database of the Chemical Abstracts Service, 

a division of the American Chemical Society.

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

49

APPENDIX 3: ANALYTICAL RESULTS 

Table A-3a: Average concentrations of samples collected in the spraying zone (installers 

or appliers) 

Table A-3b: Analytical results from outside the spraying zone (assistants) 

Table A-3c: Analytical results from outside the spraying zone (other workers) 

Table A-3d: Analytical results post-spraying by floor 

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

51

Table A-3a: Average concentrations of samples in the spraying zone (installers or appliers)

Site Work Process Duration 

(min)

MDI concentration (μg/m3)25

Monomer Oligomers Vapours

1 commercial outdoor Insulation 58 20.50 13.00 0.02 

1 commercial outdoor Insulation 101 56.87 37.48 0.02 

2 commercial outdoor Insulation 68 30.00 15.00 0.16 

3 commercial outdoor Insulation 126 41.50 10.20 0.04 

3 commercial outdoor Insulation 126 79.96 34.98 0.03 

3 commercial outdoor Insulation 52 26.00 29.00 0.16 

4 residential indoors Insulation 26 22.01 3.07 

4 residential indoors Insulation 78 36.97 20.17 

4 residential indoors Insulation 72 45.00 20.00 

5 residential indoors Insulation 84 84.61 27.37 

5 residential indoors Insulation 74 110.00 45.00 

6 residential indoors Insulation 85 16.51 5.50 

6 residential indoors Insulation 82 55.00 20.00 

6 residential indoors Insulation 49 350.10 180.00 

7 commercial outdoor Insulation 55 100.00 60.00 

7 commercial outdoor Insulation 40 30.69 10.48 

8b commercial outdoor Insulation 95 18.50 12.50 

8b commercial outdoor Insulation 80 24.53 18.65 

8a commercial outdoor Insulation 161 11.00 4.09 

9 commercial outdoor Insulation 121 75.19 29.50 

9 commercial outdoor Insulation 90 95.00 60.00 

12b residential indoors Sealing 77 15.00 6.00 0.36 

12b residential indoors Sealing 74 40.00 20.00 0.36 

12b residential indoors Sealing 75 30.20 14.61 0.27 

12a residential indoors Sealing 39 1.80 0.67 0.16 

12a residential indoors Sealing 80 40.06 15.03 0.29 

12a residential indoors Sealing 97 20.00 12.50 0.32 

13 commercial outdoor Insulation 125 75.12 40.08 0.24 

13 commercial outdoor Insulation 120 20.00 8.00 0.09 

13 commercial outdoor Insulation 77 45.16 17.08 0.28 

13 commercial outdoors Insulation 60 64.71 5.28 0.34 

14 residential indoors Sealing 44 120.10 70.10 0.69 

14 residential indoors Sealing 73 430.00 260.00 0.05 

16 commercial outdoors Insulation 71 32.93 19.05 

16 commercial outdoors Insulation 76 11.15 5.67 

17 residential indoors Sealing 60 57.50 28.50 3.05 

17 residential indoors Sealing 55.5 37.42 14.42 1.31 

18 residential indoors Sealing 119 140.13 65.57 2.25 

 

25 The MDI concentrations are the averages of the analytical results obtained from the two sampling trains 

surrounding the installer's zone (see Methodology). 
52 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

Site Work Process

Duration

(min)

MDI concentration (μg/m3)

Monomer Oligomers Vapours

19b residential indoors Insulation 106 304.86 165.05 

19b residential indoors Insulation 86 397.73 214.48 

19b residential indoors Insulation 97 348.31 189.23 14.00 

19a residential indoors Insulation 78 571.10 310.58 36.48 

19a residential indoors Insulation 75 591.28 330.60 26.00 

19a residential indoors Insulation 90 309.61 174.81 19.50 

20 residential indoors Insulation 54 116.22 69.12 

21 residential indoors Sealing 37 54.50 17.00 1.02 

21 residential indoors Insulation 57 225.00 86.50 2.65 

21 residential indoors Sealing 47 81.00 30.50 2.05 

 μ 114.8 59.3 4.0

 s 147.0 82.6 9.0

 Median 54.8 20.1 0.33

Two series of analytical results were rejected.
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

53

Table A-3b: Analytical results of samples collected outside the spraying zone (assistants) 

Site Work Process Duration 

(min)

MDI concentration (μg/m3)

Monomer Oligomers Vapours

25 commercial outdoors Insulation 69 84.00 56.00 

25 commercial outdoors Insulation 58 41.00 29.00 

25 commercial outdoors Insulation 109 4.00 0.26 

26 commercial outdoors Insulation 67 30.00 20.00 0.02 

27 commercial outdoors Insulation 125 50.00 20.00 0.04 

28 residential indoors Insulation 113 2.90 

28 residential indoors Insulation 115 3.70 

28 residential indoors Insulation 67 7.00 

30b residential indoors Sealing 74 5.00 2.00 0.25 

30b residential indoors Sealing 77 20.00 9.00 0.20 

30a residential indoors Sealing 38 3.00 0.69 0.12 

30a residential indoors Sealing 80 2.00 0.33 0.09 

30a residential indoors Sealing 107 4.00 1.00 0.23 

33 commercial outdoors Insulation 71 32.93 19.05 

33 commercial outdoors Insulation 76 11.15 5.67 

34b residential indoors Insulation 107 150.00 85.00 

34b residential indoors Insulation 244 8.90 

34b residential indoors Insulation 81 170.00 99.00 

34b residential indoors Insulation 101 150.00 82.00 11.00 

34a residential indoors Insulation 82 130.00 78.00 15.00 

34a residential indoors Insulation 69 170.00 93.00 9.30 

34a residential indoors Insulation 95 25.00 14.00 3.70 

35 residential indoors Insulation 51 88.00 60.00 

36 residential indoors Sealing 39 40.00 13.00 0.97 

36 residential indoors Insulation 57 120.00 33.00 0.04 

36 residential indoors Sealing 47 130.00 50.00 0.01 

37 commercial outdoors Insulation 121 75.19 29.50 

37 commercial outdoors Insulation 90 95.00 60.00 

 μ 67.9 35.8 3.3

 s 58.5 33.0 4.6

 Median 45.5 24.5 0.25
54 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

- IRSST

Table A-3c: Analytical results outside the spraying zone (other workers) 

MDI concentration (μg/m3)

Monomer Oligomers HS vapours

 0.14 

 0.26 

 3.8 

 6.1 

 0.51 

 11.0 

 3.0 

 4.3 

 5.6 

 2.5 

 0.14 

 0.01 

 0.01 

 0.03 

 0.03 

 0.35 

 0.16 

 0.18 

 0.08 

 0.01 

 0.05 

 0.14 

 0.04 

 0.05 

60 20 

 0.10 

 0.37 

50 10 

20 1.39 

50 25 

20 20 

20 8 

 0.12 

20 15 

25 12 

 0.13 

 0.02 

μ: 33.1 13.9 1.4

s: 17.1 7.6 2.6

Median 22.5 13.5 0.1
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

55

Table A-3d: Analytical results post-spraying by floor 

Location Time 

(min)

MDI concentration 

 HS vapours (μg/m3) Average

Same floor as foam spraying 

30 

1.90 

0.36 

0.01 

0.06 

0.02 

0.29 

0.44 

0.07 

0.01 0.350

60 0.23 

0.23 

0.02 

0.02 

0.02 

0.03 

0.02 0.078

120 0.04 

0.01 

0.01 

0.08 

0.01 0.029

240 0.06 

On another floor than 

foam spraying 

30 0.02 

0.58 0.302

60 2.40 * 

0.39 

0.06 0.951

120 0.01 

0.01 

0.04 0.022

*: This sampling was carried out over the 60-minute period after the end of spraying.

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 

polyurethane foam spraying 

57

APPENDIX 4: DATA FROM THE STATISTICAL ANALYSIS OF THE MDI 

RESULTS 

Table A-4a: Results of the statistical analysis by determining factor for the daily average 

exposure by task (monomer MDI) 

Table A-4b: Results of the statistical analysis by determining factor for the average 

concentration of the samples by task (Monomer MDI) 

Table A-4c: Results of the statistical analysis by determining factor for the average daily 

exposure by task (MDI oligomers) 

Table A-4d: Results of the statistical analysis by determining factor for the average 

concentration of the samples by task (MDI oligomers) 

IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during polyurethane foam s

Table A-4a: Results of the statistical analysis by determining factor for the average daily exposu

Task

Location

Season

Foam

Parameter

Number (n)

Maximum (μg/m3)

Minimum (μg/m3)

Arithmetic mean

(μg/m3)

Median (μg/m3)

Standard deviation (s)

Geometric mean

(μg/m3)

Geometric standard 

deviation (GSD)

W test on logt

fd dt

Installer Indoors B-2 DAE-mono 7 76.4 10.9 27.5 14.0 23.7 21.3 2.09 0.8

Outdoors summer DAE-mono 7 31.9 4.3 14.7 14.0 9.4 11.9 2.12 0.8

Assistant Outdoors DAE-mono 5 36.8 4.3 15.7 13.0 12.9 11.9 2.32 0.9Installer Indoors winter DAE-mono 5 76.4 10.9 29.4 13.3 28.1 21.3 2.35 0.8Installer Indoors winter B-2 DAE-mono 5 76.4 10.9 29.4 13.3 28.1 21.3 2.35 0.8

Outdoors A-1 DAE-mono 5 31.9 4.3 13.5 13.0 11.3 10.1 2.36 0.8

A-1 DAE-mono 6 48.1 4.3 19.3 13.5 17.4 13.1 2.71 0.92 

 summer A-1 DAE-mono 6 48.1 4.3 19.3 13.5 17.4 13.1 2.71 0.92 

Indoors summer DAE-mono 11 243 9.4 71.2 38.9 80.5 42.2 2.90 0.94 

Installer Indoors DAE-mono 12 243 10.9 62.1 33.3 79.4 34.1 2.97 0.8

 summer DAE-mono 18 243 4.3 49.2 24.1 68.1 25.8 3.09 0.9

Installer Indoors summer DAE-mono 7 243 13.1 85.4 38.9 97.4 47.6 3.22 0.8

Indoors B-2 DAE-mono 9 76.4 1.5 22.0 13.3 23.3 13.2 3.23 0.9Outdoors DAE-mono 16 36.8 0.3 15.1 13.5 11.7 9.8 3.32 0.8

Assistant DAE-mono 11 93.7 1.5 24.5 13.0 27.9 13.1 3.48 0.9

Indoors winter DAE-mono 7 76.4 1.5 21.8 11.5 26.4 11.5 3.66 0.9Indoors DAE-mono 18 243 1.5 52.0 31.0 68.3 25.5 3.67 0.9

B-2 DAE-mono 18 76.4 0.3 18.7 12.4 18.9 10.5 3.75 0.9

DAE-mono 34 243 0.3 34.6 15.7 53.1 16.1 3.77 0.9

Installer B-2 DAE-mono 14 76.4 0.3 20.6 13.7 19.7 12.2 3.77 0.8Installer Outdoors DAE-mono 11 36.8 0.3 14.8 14.0 11.8 8.9 3.90 0.8

winter DAE-mono 16 76.4 0.3 18.2 11.2 19.8 9.6 3.94 0.94 winter B-2 DAE-mono 16 76.4 0.3 18.2 11.2 19.8 9.6 3.94 0.94 

A-2 DAE-mono 6 243 9.4 103.3 72.7 100.5 55.8 3.96 0.92 
60 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration dur

Task

Location

Season

Foam

Parameter

Number (n)

Maximum (μg/m3)

Minimum (μg/m3)

Arithmetic mean

(μg/m3)

Median (μg/m3)

Standard deviation (s)

Geometric mean

(μg/m3)

Geometric standard 

deviation (GSD)

W test on logt

fd dt

Indoors A-2 DAE-mono 6 243 9.4 103.3 72.7 100.5 55.8 3.96 0.92 

summer A-2 DAE-mono 6 243 9.4 103.3 72.7 100.5 55.8 3.96 0.92 

Installer DAE-mono 23 243 0.3 39.5 17.3 61.6 17.9 3.97 0.9

Outdoors winter DAE-mono 9 36.8 0.3 15.4 7.8 13.9 8.4 4.44 0.8Outdoors B-2 DAE-mono 9 36.8 0.3 15.4 7.8 13.9 8.4 4.44 0.8

Assistant Indoors DAE-mono 6 93.7 1.5 31.7 19.8 35.8 14.2 4.90 0.9Installer Outdoors winter DAE-mono 7 36.8 0.3 13.6 7.8 12.8 7.0 4.94 0.8Installer Outdoors B-2 DAE-mono 7 36.8 0.3 13.6 7.8 12.8 7.0 4.94 0.8Installer Outdoors winter B-2 DAE-mono 7 36.8 0.3 13.6 7.8 12.8 7.0 4.94 0.8
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during polyurethane foam s

Table A-4b: Results of the statistical analysis by determining factor for the average concentration 

monomer) 

Task

Location

Season

Foam

Parameter

Number (n)

Maximum (μg/m3)

Minimum (μg/m3)

Arithmetic mean

(μg/m3)

Median (μg/m3)

Standard deviation (s)

Geometric mean

(μg/m3)

Geometric standard 

deviation (GSD)

W test on logtransformed data

Outdoors summer Conc mono 7 70.8 30.0 45.3 39.3 15.8 43.1 1.40 0.92 YOutdoors A-1 Conc mono 5 70.8 30.0 48.3 50.0 18.3 45.4 1.49 0.86 Y

A-1 Conc mono 6 106.8 30.0 58.1 55.4 28.9 52.4 1.65 0.94 Y

summer A-1 Conc mono 6 106.8 30.0 58.1 55.4 28.9 52.4 1.65 0.94 Y

Assistant Outdoors Conc mono 5 83.6 21.7 44.4 36.5 24.3 39.8 1.67 0.98 Y

Indoors summer Conc mono 11 480.5 38.0 160.3 106.8 132.0 127.2 1.98 0.89 Y

A-2 Conc mono 6 480.5 88.0 214.7 135.9 161.5 172.9 2.01 0.89 Y

Indoors A-2 Conc mono 6 480.5 88.0 214.7 135.9 161.5 172.9 2.01 0.89 Y

summer A-2 Conc mono 6 480.5 88.0 214.7 135.9 161.5 172.9 2.01 0.89 Ysummer Conc mono 18 480.5 30.0 115.6 92.3 116.9 83.5 2.18 0.93 Y

Outdoors Conc mono 16 83.6 3.8 42.3 37.3 25.6 33.3 2.27 0.89 Y

Installer Indoors summer Conc mono 7 480.5 38.0 188.2 116.2 161.6 139.0 2.33 0.93 YInstaller Outdoors Conc mono 11 83.6 3.8 41.4 38.0 27.3 30.8 2.55 0.9 YInstaller Indoors B-2 Conc mono 7 313.5 24.1 98.3 47.9 103.8 65.6 2.56 0.93 YInstaller Indoors Conc mono 12 480.5 24.1 155.9 111.5 146.0 103.1 2.67 0.95 Y

Outdoors winter Conc mono 9 83.6 3.8 40.0 21.7 32.0 27.3 2.81 0.91 YOutdoors B-2 Conc mono 9 83.6 3.8 40.0 21.7 32.0 27.3 2.81 0.91 Y

Installer Outdoors winter Conc mono 7 83.6 3.8 36.4 21.7 31.3 24.0 2.97 0.94 YInstaller Outdoors B-2 Conc mono 7 83.6 3.8 36.4 21.7 31.3 24.0 2.97 0.94 YInstaller Outdoors winter B-2 Conc mono 7 83.6 3.8 36.4 21.7 31.3 24.0 2.97 0.94 YInstaller Indoors winter Conc mono 5 313.5 24.1 110.8 47.9 122.7 67.8 3.00 0.91 YInstaller Indoors winter B-2 Conc mono 5 313.5 24.1 110.8 47.9 122.7 67.8 3.00 0.91 YInstaller B-2 Conc mono 14 313.5 3.8 67.3 38.0 80.4 39.7 3.02 0.98 Y
62 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration dur

Task

Location

Season

Foam

Parameter

Number (n)

Maximum (μg/m3)

Minimum (μg/m3)

Arithmetic mean

(μg/m3)

Median (μg/m3)

Standard deviation (s)

Geometric mean

(μg/m3)

Geometric standard 

deviation (GSD)

W test on logtransformed data

Installer Conc mono 23 480.5 3.8 101.2 60.7 120.0 57.8 3.08 0.98 Y

Conc mono 34 481 3.1 88.4 55.4 103.0 51.1 3.14 0.97 Y

Assistant Conc mono 11 155.6 3.1 61.7 50.0 47.7 39.4 3.30 0.9 Y

B-2 Conc mono 18 313.5 3.1 58.9 33.1 73.8 31.8 3.36 0.97 Y

winter Conc mono 16 313.5 3.1 57.8 26.2 77.8 29.4 3.50 0.98 Ywinter B-2 Conc mono 16 313.5 3.1 57.8 26.2 77.8 29.4 3.50 0.98 Y

Indoors Conc mono 18 480.5 3.1 129.4 101.1 127.7 74.6 3.57 0.92 YIndoors B-2 Conc mono 9 313.5 3.1 77.7 38.0 98.8 37.2 4.11 0.98 YIndoors winter Conc mono 7 313.5 3.1 80.7 28.2 112.6 32.3 4.84 0.98 Y

Assistant Indoors Conc mono 6 155.6 3.1 76.2 94.4 59.4 39.2 5.08 0.8 Y
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during polyurethane foam s

Table A-4c: Results of the statistical analysis by determining factor for the average daily exposu

Task

Location

Season

Foam

Parameter

Number (n)

Maximum (max) (μg/m3)

Minimum (min) (μg/m3)

Arithmetic mean

(μg/m3)

Median (μg/m3)

Standard deviation (s)

Geometric mean

(μg/m3)

Geometric standard 

deviation(GSD)

W test on log-transformed 

data

Lognormal l(α= 0.05)?

Outdoors A-1 DAE oli 5 11.9 2.1 5.8 5.2 4.12 4.6 2.2 0.89 Yes Outdoors summer DAE oli 7 12.6 2.1 7.6 7.8 4.56 6.1 2.2 0.82 Yes 

Installer Indoors B-2 DAE oli 7 46.0 5.1 13.9 6.4 14.74 9.9 2.2 0.84 Yes Assistant Outdoors DAE oli 5 18.7 2.1 8.3 5.2 6.85 6.2 2.4 0.97 Yes 

A-1 DAE oli 6 22.8 2.1 8.6 6.5 7.84 6.1 2.6 0.94 Yes 

summer A-1 DAE oli 6 22.8 2.1 8.6 6.5 7.84 6.1 2.6 0.94 Yes 

Installer Indoors winter DAE oli 5 46.0 5.1 15.8 6.3 17.51 10.5 2.6 0.83 Yes Installer Indoors winter B-2 DAE oli 5 46.0 5.1 15.8 6.3 17.51 10.5 2.6 0.83 Yes 

Outdoors DAE oli 16 18.7 0.3 7.6 5.5 5.83 5.1 3.0 0.91 Yes Indoors summer DAE oli 11 139.9 6.4 37.7 14.6 46.36 20.7 3.0 0.9 Yes 

summer DAE oli 18 139.9 2.1 26.0 11.7 38.73 12.9 3.1 0.93 Yes 

Installer Indoors DAE oli 12 139.9 5.1 32.9 13.2 45.52 16.4 3.2 0.87 Yes Installer B-2 DAE oli 14 46.0 0.3 10.2 6.0 11.55 6.0 3.3 0.91 Yes Installer Outdoors DAE oli 11 18.7 0.3 7.3 5.6 5.65 4.6 3.4 0.9 Yes Installer Indoors summer DAE oli 7 139.9 6.4 45.2 14.6 56.34 22.7 3.5 0.86 Yes 

A-2 DAE oli 6 139.9 6.4 58.3 41.2 56.17 32.7 3.7 0.92 Yes 

Indoors A-2 DAE oli 6 139.9 6.4 58.3 41.2 56.17 32.7 3.7 0.92 Yes 

summer A-2 DAE oli 6 139.9 6.4 58.3 41.2 56.17 32.7 3.7 0.92 Yes 

Outdoors B-2 DAE oli 9 18.7 0.3 7.5 5.4 6.94 4.4 3.7 0.91 Yes Outdoors winter DAE oli 9 18.7 0.3 7.5 5.4 6.94 4.4 3.7 0.91 Yes 

Installer DAE oli 23 139.9 0.3 20.7 7.8 34.97 9.0 3.8 0.95 Yes Installer Outdoors B-2 DAE oli 7 18.7 0.3 6.5 5.4 6.31 3.7 4.0 0.93 Yes Installer Outdoors winter B-2 DAE oli 7 18.7 0.3 6.5 5.4 6.31 3.7 4.0 0.93 Yes Installer Outdoors winter DAE oli 7 18.7 0.3 6.5 5.4 6.31 3.7 4.0 0.93 Yes 
64 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration dur

Task

Location

Season

Foam

Parameter

Number (n)

Maximum (max) (μg/m3)

Minimum (min) (μg/m3)

Arithmetic mean

(μg/m3)

Median (μg/m3)

Standard deviation (s)

Geometric mean

(μg/m3)

Geometric standard

deviation (GSD)

W test on logtransformed data

Lognormal (α = 0.05) ?

DAE oli 34 139.9 0.1 18.1 7.8 30.08 7.6 4.3 0.94 Yes 

B-2 DAE oli 18 46.0 0.1 9.3 5.5 10.86 4.6 4.6 0.89 No 

winter B-2 DAE oli 16 46.0 0.1 9.3 5.3 11.52 4.2 5.0 0.91 Yes winter DAE oli 16 46.0 0.1 9.3 5.3 11.52 4.2 5.0 0.91 Yes 

Indoors DAE oli 18 139.9 0.1 27.5 10.8 39.08 11.0 5.4 0.89 No 

Assistant DAE oli 11 52.9 0.1 12.9 6.4 15.84 5.4 5.8 0.9 Yes 

Indoors B-2 DAE oli 9 46.0 0.1 11.0 6.3 13.99 4.8 6.0 0.85 Yes Indoors winter DAE oli 7 46.0 0.1 11.5 5.2 16.03 4.0 7.6 0.89 Yes 

Assistant Indoors DAE oli 6 52.9 0.1 16.8 8.1 20.62 4.9 10.6 0.92 Yes 
IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during polyurethane foam s

Table A-4d: Results of the statistical analysis by determining factor for the average concentratio

oligomers) 

Task

Location

Season

Foam

Parameter

Number (n)

Maximum (max)

Minimum (min)

Arithmetic mean

(μg/m3)

Median

Standard deviation (s)

Geometric mean

(μg/m3)

Geometric standard 

deviation (GSD)

W test on logtransformed data

Lognormal (α= 0.05)?

Outdoors summer Conc Oli 7 39.2 15.0 23.4 22.6 8.46 22.2 1.4 0.94 Yes Outdoors A-1 Conc Oli 5 39.2 15.0 22.3 20.0 9.95 20.9 1.5 0.87 Yes 

Assistant Outdoors Conc Oli 5 42.5 12.1 22.7 20.0 11.95 20.5 1.6 0.96 Yes 

A-1 Conc Oli 6 50.6 15.0 27.1 21.3 14.56 24.2 1.7 0.9 Yes 

summer A-1 Conc Oli 6 50.6 15.0 27.1 21.3 14.56 24.2 1.7 0.9 Yes 

A-2 Conc Oli 6 266.5 57.5 120.5 75.5 86.73 99.6 1.9 0.84 Yes 

Indoors A-2 Conc Oli 6 266.5 57.5 120.5 75.5 86.73 99.6 1.9 0.84 Yes 

summer A-2 Conc Oli 6 266.5 57.5 120.5 75.5 86.73 99.6 1.9 0.84 Yes 

Indoors summer Conc Oli 11 266.5 17.6 82.7 57.5 75.64 61.9 2.1 0.94 Yes 

summer Conc Oli 18 266.5 15.0 59.6 37.4 65.37 41.6 2.2 0.93 Yes 

Installer Indoors summer Conc Oli 7 266.5 17.6 96.7 50.6 93.30 66.0 2.6 0.95 Yes Installer Indoors B-2 Conc Oli 7 188.6 11.3 50.5 21.7 63.69 30.7 2.7 0.91 Yes Installer Indoors Conc Oli 12 266.5 11.3 81.5 50.1 84.59 49.6 2.9 0.94 Yes Installer Indoors winter Conc Oli 5 188.6 11.3 60.1 21.7 75.11 33.3 3.3 0.9 Yes Installer Indoors winter B-2 Conc Oli 5 188.6 11.3 60.1 21.7 75.11 33.3 3.3 0.9 Yes 

Outdoors Conc Oli 16 42.5 0.2 21.0 17.7 14.10 13.5 3.9 0.76 No 

Assistant Conc Oli 11 81.9 0.7 31.8 23.6 25.91 18.6 4.0 0.87 Yes 

Indoors Conc Oli 18 266.5 0.7 67.5 50.1 73.21 34.7 4.2 0.91 Yes 

Conc Oli 34 266.5 0.2 45.6 26.1 58.35 22.3 4.3 0.91 No 

Installer Conc Oli 23 266.5 0.2 52.2 28.7 68.28 24.3 4.5 0.9 No Installer Outdoors Conc Oli 11 42.5 0.2 20.3 15.3 15.46 11.2 4.9 0.8 No 

Indoors B-2 Conc Oli 9 188.6 0.7 39.8 17.6 59.14 16.0 5.0 0.97 Yes 

Installer B-2 Conc Oli 14 188.6 0.2 33.7 16.4 48.17 14.7 5.1 0.9 Yes 
66 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration dur

Task

Location

Season

Foam

Parameter

Number (n)

Maximum (max)

Minimum (min)

Arithmetic mean

(μg/m3)

Median

Standard deviation (s)

Geometric mean

(μg/m3)

Geometric standard 

deviation (GSD)

W test on logtransformed data

Lognormal (α = 0.05) ?

B-2 Conc Oli 18 188.6 0.2 29.5 14.4 43.64 12.1 5.2 0.93 Yes 

Outdoors B-2 Conc Oli 9 42.5 0.2 19.1 12.1 17.60 9.2 5.5 0.84 Yes Outdoors winter Conc Oli 9 42.5 0.2 19.1 12.1 17.60 9.2 5.5 0.84 Yes 

winter B-2 Conc Oli 16 188.6 0.2 29.8 12.8 46.33 11.0 5.6 0.95 Yes winter Conc Oli 16 188.6 0.2 29.8 12.8 46.33 11.0 5.6 0.95 Yes 

Indoors winter Conc Oli 7 188.6 0.7 43.6 13.4 67.53 14.0 6.2 0.98 Yes 

Installer Outdoors B-2 Conc Oli 7 42.5 0.2 16.8 12.1 17.54 7.1 6.4 0.89 Yes Installer Outdoors winter B-2 Conc Oli 7 42.5 0.2 16.8 12.1 17.54 7.1 6.4 0.89 Yes Installer Outdoors winter Conc Oli 7 42.5 0.2 16.8 12.1 17.54 7.1 6.4 0.89 Yes Assistant Indoors Conc Oli 6 81.9 0.7 39.5 45.3 32.76 17.1 6.8 0.83 Yes