ISO/TR 17737:2007
(Main)Workplace air — Guidelines for selecting analytical methods for sampling and analysing isocyanates in air
Workplace air — Guidelines for selecting analytical methods for sampling and analysing isocyanates in air
ISO/TR 17737:2007 provides guidelines which are intended to provide industrial hygienists, employers and workers with a broad overview of isocyanates, their uses in industry, methods of measurement and guidance on choosing the appropriate sampling strategy. This document discusses areas of concern to alert the industrial hygienist, employer and worker involved with the use of isocyanates to the importance of sampling and the key issues involved in choosing a sampling strategy for their workplace, and directs them to seek further information on the topic(s) of concern.
Atmosphères des lieux de travail — Lignes directrices pour la sélection des méthodes analytiques d'échantillonnage et d'analyses des isocyanates dans l'air
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Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 17737
First edition
2007-04-01
Workplace air — Guidelines for selecting
analytical methods for sampling and
analysing isocyanates in air
Atmosphères des lieux de travail — Lignes directrices pour la sélection
des méthodes analytiques d'échantillonnage et d'analyses des
isocyanates dans l'air
Reference number
ISO/TR 17737:2007(E)
©
ISO 2007
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ISO/TR 17737:2007(E)
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ii © ISO 2007 – All rights reserved
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ISO/TR 17737:2007(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Isocyanates . 1
3 Where are isocyanates found in industry? .2
4 Airborne isocyanates . 3
5 Alternatives for sampling. 4
5.1 General. 4
5.2 Impregnated filters. 4
5.3 Impinger (and filter) . 4
5.4 Sorbent tubes. 4
5.5 Denuder filter. 4
5.6 Diffusive sampling. 5
6 Direct reading instruments . 5
7 Short description of four proposed and/or adopted methods for airborne isocyanates. 5
7.1 DBA method . 5
7.2 Double-filter method. 6
7.3 MAP method . 6
7.4 MP method. 6
8 Analysis . 8
9 Interferences . 8
10 Other sampling and analytical considerations. 8
11 Other considerations. 8
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ISO/TR 17737:2007(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In exceptional circumstances, when a technical committee has collected data of a different kind from that
which is normally published as an International Standard (“state of the art”, for example), it may decide by a
simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely
informative in nature and does not have to be reviewed until the data it provides are considered to be no
longer valid or useful.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO/TR 17737 was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 2,
Workplace atmospheres.
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TECHNICAL REPORT ISO/TR 17737:2007(E)
Workplace air — Guidelines for selecting analytical methods for
sampling and analysing isocyanates in air
1 Scope
The topic of measuring airborne isocyanates is complicated. Finding the most appropriate sampling strategy
and method to use to assess the air concentration of a particular isocyanate product can be daunting. The
guidelines in this Technical Report are intended to provide industrial hygienists, employers and workers with a
broad overview of isocyanates, their uses in industry, methods of measurement and guidance on choosing the
appropriate sampling strategy. While not all issues can be addressed here in detail, this Technical Report
discusses areas of concern to alert the industrial hygienist, employer and worker involved with the use of
isocyanates to the importance of sampling and the key issues involved in choosing a sampling strategy for
their workplace, and directs them to seek further information on the topic(s) of concern.
2 Isocyanates
Isocyanates are compounds which contain one or more −N=C=O functional groups attached to an aromatic or
an aliphatic molecule. Compounds containing nucleophilic groups with active hydrogen react readily with
isocyanates, as in the reaction with primary and secondary amines to form urea compounds and the reaction
with alcohols and phenols to form urethane compounds.
a) Reaction with an alcohol to form a urethane
b) Reaction with an amine to form a urea
c) Reaction with water to form the corresponding amine
Figure 1 — Reactions of isocyanates
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ISO/TR 17737:2007(E)
Exposures to isocyanates may result in respiratory disorders and dermal sensitization and are one of the main
causes of occupational asthma. As a result, isocyanates are among the compounds with the lowest
occupational exposure limits (OELs), the maximum exposure level recommended to avoid unreasonable risk
of disease or injury. Their presence in different exposure situations must be monitored.
3 Where are isocyanates found in industry?
Isocyanates with a functionality (number of NCO groups) of two or more are used in the production of
polyurethanes (PUR). The most common isocyanates used in the production of flexible and rigid PUR foams
are the aromatic methylenediphenyl diisocyanate (MDI) and toluene diisocyanate (TDI). The two major
aliphatic isocyanates, which are used predominantly in coatings and elastomers, are hexamethylene
diisocyanate (HDI) and isophorone diisocyanate (IPDI).
Within industry, technical grade isocyanate products are mainly used. In most cases, these products consist of
different monomeric isomers and oligoisocyanates that have different functionalities, and are often referred to
as polyisocyanates of the diisocyanate monomer. The most frequently used TDI products consist of two
isomers, 2,4- and 2,6-TDI. Technical MDI products, often referred to as polymeric MDI (pMDI), are mixtures of
monomeric MDI isomers and higher molecular mass polyisocyanates. Technical HDI products used in
applications such as spray-painting typically contain less than 1 % of the HDI monomer, with the major
components HDI isocyanurate and/or HDI biuret and oligomers thereof. Another route to polyisocyanate
production is the reaction of di- or polyfunctional alcohols with an excess of isocyanate molecules, which
results in prepolymer mixtures of isocyanates. In addition to improved chemical handling properties,
prepolymers also reduce the risk of exposure to vapours from the isocyanate by reducing the amount of
monomer present in the product.
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ISO/TR 17737:2007(E)
Table 1 — Examples of activities/industries where isocyanates are used and/or generated
Activity/industry “Cold” handling “Hot” handling
Painting, filling, sealing, windscreen
assembly, bonding, manufacturing of
Automotive industry, ships, aircraft and Cutting, welding, grinding, windscreen
composites, roof-liner pressing,
trains removal, removal of underseal
acoustic panel processing, truck bed
lining
Sealing, bonding, painting, caulking, Handling of mineral wool, mat welding,
Building floor and wall coverings, insulation and copper pipe welding, paint removal,
roofing pipe insulation
Manufacture of PUR-textile, shoes and
Clothing and leisure industry Flame lamination
sports grounds and equipment
Soldering circuit boards, connecting
Electrical and electronics Packaging, gluing, casting optical fibres and varnished wires, cable
insulation, heating Bakelite
Manufacturing, automotive and Removal of paints and varnishes with
Paint industry
industrial painting heat
Manufacturing with hot-box technique,
Foundry Manufacturing of cold-box cores
casting cores and shell sand
Manufacturing of printing inks,
Graphic trades Curing, lamination
lamination
Repair of conveyors, heat sealing of
Foodstuffs Food packaging
packaging materials
Manufacture of foam, automotive
Plastics industry Hot wire cutting
fittings
Tunnelling and mining Sealing, rock consolidation Self-ignition may occur
Manufacture of composite wood
Pressing, cutting and routing, removal
Wood and furniture panels, use of adhesives, varnishing,
of paints and varnishes with hot air gun
upholstery padding, painting
Gluing, manufacture of elastomers, Repairs and removal of polyurethane
Engineering
painting, insulation, fixatives materials with heat
Manufacture of refrigerators and Mineral wool insulation – Quality
White goods industry
freezers (PUR insulation), painting assurance (QA) checks, repairs
Medical care Bandaging, casting, filling, equipment
Mineral wool, polyurethane in furniture
Fire extinguishing
and interior fittings
4 Airborne isocyanates
Airborne isocyanates in workplace atmospheres can occur both in the gas and particle phase. The distribution
depends on the physical properties of the isocyanate and on the nature of the work tasks that introduce
isocyanates into the air. Monomeric TDI and HDI have vapour pressures (at room temperature) that are
sufficient to contribute to air levels of gas-phase isocyanates above the OELs; whereas MDI, adducts of HDI,
and prepolymers have vapour pressures that are much lower and, consequently, the gas phase levels will be
lower than the OELs (at room temperature). If aerosolization occurs, the air concentrations can be higher than
the OEL even if the vapour pressures are low. Airborne particles containing isocyanates can also contain
polyols and other ingredients of the formulation that can react with the isocyanates (reacting aerosol).
Polyurethanes start to thermally degrade at temperatures above 150 °C to 200 °C, possibly resulting in the
emission of monomeric diisocyanates, monoisocyanates, aminoisocyanates, and amines both in gas and
particle phases. Like polyurethanes, urea based resins can also release isocyanates when heated and
material safety data sheets may not contain sufficient information regarding compounds that can be formed
during thermal decomposition.
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ISO/TR 17737:2007(E)
5 Alternatives for sampling
5.1 General
Great care must be taken to ensure that representative samples are collected. The analyst and/or industrial
hygienist must consider the physical state of the isocyanate(s) likely to be present in the atmosphere being
sampled. For example, the isocyanate(s) may be present as a vapour and/or aerosol, or the isocyanate may
be coated on another medium, e.g. wood dust. All the above must be considered when selecting a method for
monitoring workplace exposures.
The mechanisms for sampling compounds in the gas and particle phase differ. Gas phase compounds are
typically collected by diffusion of molecules to a solid or liquid surface within the sampler. Collection of
airborne particles is typically achieved by filtration or by impaction.
5.2 Impregnated filters
Filter sampling with a filter impregnated with a derivatizing reagent is commonly used for the collection of
isocyanates. Both gas and particle-borne isocyanates can be efficiently collected. However, in some
circumstances when collecting particles, incomplete derivatization with the reagent may occur due to the
presence of other reactive species in the particle. In these instances, field extraction immediately after
sampling improves the derivatization and minimises problems with interfering reactions. If the
physical/chemical composition of the air being sampled is unknown, samples should be collected using an
impinger containing a derivatizing agent with filter backup (see 5.3). Reagent-impregnated filters are
recommended for gas-phase isocyanates.
5.3 Impinger (and filter)
Sampling with a typical industrial hygiene midget impinger containing a derivatizing agent with a reagent-
coated filter [except for di-n-butylamine (DBA)] in series enables the collection of gas- and particle-phase
isocyanates.
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