ISO 7203-4:2022

INTERNATIONAL ISO
STANDARD 7203-4
First edition
2022-02
Corrected version
2022-03
Fire extinguishing media — Foam
concentrates —
Part 4:
Specification for Class A foam
concentrates for application on Class
A fires
Agents extincteurs — Émulseurs —
Partie 4: Spécifications pour les agents émulseurs destinés à une
application par les matières solide combustible
Reference number
ISO 7203-4:2022(E)
© ISO 2022

---------------------- Page: 1 ----------------------
ISO 7203-4:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
  © ISO 2022 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 7203-4:2022(E)
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Type and use of Class A foam concentrates . 3
4.1 General . 3
4.2 Use with sea water . 3
5 Tolerance of the foam concentrate to freezing and thawing . 3
6 Sediment in the foam concentrate .4
6.1 Sediment before ageing . 4
6.2 Sediment after ageing. 4
7 Determination of viscosity .4
7.1 Newtonian foam concentrates . 4
7.2 Pseudo-plastic foam concentrates . 4
8 pH of the foam concentrate . 4
8.1 pH limits . 4
8.2 Sensitivity to temperature . . 4
9 Surface tension of the foam solution . 4
9.1 Before temperature conditioning . 4
9.2 Temperature sensitivity . . 5
10 Expansion and drainage of foam .5
10.1 Expansion . 5
10.1.1 Limits . 5
10.2 Drainage . 5
10.2.1 Limits . 5
11 Test fire performance . .5
12 Corrosion . 5
13 Toxicology and environmental information . 5
14 Marking, packaging and specification sheet . 5
14.1 Marking . 5
14.2 Packaging . 6
14.3 Specification sheet . 6
Annex A (normative) Preliminary sampling and conditioning of the foam concentrate .7
Annex B (normative) Determination of tolerance to freezing and thawing .8
Annex C (normative) Determination of percentage of sediment.10
Annex D (normative) Determination of viscosity for pseudo-plastic foam concentrates .11
Annex E (normative) Determination of surface tension .13
Annex F (normative) Determination of expansion and drainage time .14
Annex G (normative) Determination of fire test performance .20
Annex H (normative) Toxicology and environmental information .22
Annex I (informative) Compatibility .23
Annex J (normative) Determination of viscosity using a rotational viscometer with defined
shear rate .24
iii
© ISO 2022 – All rights reserved

---------------------- Page: 3 ----------------------
ISO 7203-4:2022(E)
Bibliography .28
iv
  © ISO 2022 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 7203-4:2022(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 21, Equipment for fire protection and fire
fighting, Subcommittee SC 6, Foam and powder media and firefighting system using foam and powder.
This corrected version of ISO 7203-4:2022 incorporates the following corrections:
— the publication year included on the cover page and in the headers and footers of the document
has been corrected from 2021 to 2022.
A list of all parts in the ISO 7203 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
© ISO 2022 – All rights reserved

---------------------- Page: 5 ----------------------
ISO 7203-4:2022(E)
Introduction
Firefighting foams are widely used to control and extinguish fires of flammable liquids and for
inhibiting reignition. They can also be used to prevent the ignition of flammable liquids and, in certain
conditions, extinguish fires of solid combustibles.
Foams can be used in combination with other extinguishing media, particularly halocarbons, carbon
dioxide and powders, which are the subject of other International Standards, including ISO 6183,
ISO 7201-1, ISO 7201-2 and ISO 7202. A specification for foam systems can be found in the ISO 7076
series.
Attention is drawn to Annex I, which deals with the compatibility of foam concentrates.
1)
Attention is also drawn to Annex J, which contains information previously included ISO 3219:1993
that is considered relevant to this document.
NOTE ISO 3219:1993 is currently under revision with a view to expansion into a series. The content included
in Annex J has not yet been incorporated into a new Part.
A specification for portable extinguishers can be found in ISO 7165.
1) Cancelled and replaced by ISO 3219-1:2021 and ISO 3219-2:2021.
vi
  © ISO 2022 – All rights reserved

---------------------- Page: 6 ----------------------
INTERNATIONAL STANDARD ISO 7203-4:2022(E)
Fire extinguishing media — Foam concentrates —
Part 4:
Specification for Class A foam concentrates for application
on Class A fires
1 Scope
This document specifies the essential properties and performance of liquid foam concentrates used
to make foams for the extinguishment and inhibition of reignition of fires of Class A fuels. Minimum
performance on certain test fires is specified.
NOTE 1 Class A fires are fires involving solid materials, usually of an organic nature, in which combustion
normally takes place with the formation of glowing embers (see 3.16).
NOTE 2 Class A fuels can include materials such as vegetation, wood, cloth, paper, rubber and some plastics
(see 3.17).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 304, Surface active agents — Determination of surface tension by drawing up liquid films
ISO 3104, Petroleum products — Transparent and opaque liquids — Determination of kinematic viscosity
and calculation of dynamic viscosity
ISO 3219-2, Rheology — Part 2: General principles of rotational and oscillatory rheometry
ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 7203-2, Fire extinguishing media — Foam concentrates — Part 2: Specification for medium- and high-
expansion foam concentrates for top application to water-immiscible liquids
ISO 7203-3, Fire extinguishing media — Foam concentrates — Part 3: Specification for low-expansion foam
concentrates for top application to water-miscible liquids
EN 1568-3:2018, Fire extinguishing media — Foam concentrates — Part 3: Specification for low expansion
foam concentrates for surface application to water-immiscible liquids
UNITED NATIONS (UN), Globally Harmonized System of Classification and Labelling of Chemicals, 4th
2)
revised edition (2011)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2) Available at: https:// unece .org/ fileadmin/ DAM/ trans/ danger/ publi/ ghs/ ghs _rev04/ English/ ST -SG -AC10 -30
-Rev4e .pdf.
1
© ISO 2022 – All rights reserved

---------------------- Page: 7 ----------------------
ISO 7203-4:2022(E)
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
characteristic value
value declared by the foam (3.7) concentrate supplier for the chemical and physical properties and the
performances of the foam, foam solution (3.11), and foam concentrate (3.8)
3.2
25 % drainage time
time for 25 % of the liquid content of a foam (3.7) to drain out
3.3
expansion
ratio of the volume of foam (3.7) to the volume of the foam solution (3.11) from which it was made
3.4
low-expansion
with expansion (3.3) in the range 1 to 20, as applied to foam (3.7) and to associated equipment, systems
and concentrates
3.5
medium-expansion
with expansion (3.3) in the range greater than 20 to 200, as applied to foam (3.7) and to associated
equipment, systems and concentrates
3.6
high-expansion
with expansion (3.3) greater than 200, as applied to foam (3.7) and to associated equipment, systems
and concentrates
3.7
foam
aggregate of air-filled bubbles formed from an aqueous solution of a suitable foam
concentrate (3.8)
3.8
foam concentrate
liquid that, when mixed with water in the appropriate concentration, gives a foam solution (3.11)
3.9
protein foam concentrate
P
foam concentrate (3.8) derived from hydrolysed protein materials
3.10
fluoroprotein foam concentrate
FP
protein foam concentrate (3.9) with added fluorinated surface-active agents
3.11
foam solution
solution of foam concentrate (3.8) and water
3.12
sediment
insoluble particles in the foam concentrate (3.8)
2
  © ISO 2022 – All rights reserved

---------------------- Page: 8 ----------------------
ISO 7203-4:2022(E)
3.13
spreading coefficient
value calculated from the measured surface and interfacial tensions to indicate the ability of one liquid
to spontaneously spread across the surface of another
3.14
temperature for use
maximum and minimum temperature claimed by the manufacturer between which the foam concentrate
(3.8) is ready for use
3.15
Class A foam concentrate
foam concentrate (3.8) for use on Class A fire (3.16)
Note 1 to entry: Protein foam concentrate (3.9) and fluoroprotein foam concentrate (3.10) describe types of foam
which can be used in Class A applications.
3.16
Class A fire
fires involving solid materials, usually of an organic nature, in which combustion normally takes place
with the formation of glowing embers
Note 1 to entry: See ISO 3941.
3.17
Class A fuel
solid materials, usually of an organic nature (such as vegetation, wood, cloth, paper, rubber, and some
plastics), in which combustion can occur at or below the surface of the material, with or without the
formation of glowing embers
3.18
freezing point
temperature at which the first ingredient of a mixture starts to solidify or freeze out
4 Type and use of Class A foam concentrates
4.1 General
Foam concentrates capable of providing positive fire testing results if tested in accordance with
Annex G are considered Class A foam concentrates.
4.2 Use with sea water
If a Class A foam concentrate is marked as suitable for use with sea water, the recommended
concentrations for use with fresh water and sea water shall be identical. Consider increased
corrosiveness on equipment used if foam solution is prepared using sea water.
5 Tolerance of the foam concentrate to freezing and thawing
Before and after temperature-conditioning in accordance with A.2, the foam concentrate, if it is claimed
by the supplier not to be adversely affected by freezing and thawing, shall show no visual sign of
stratification and non-homogeneity when tested in accordance with Annex B.
Foam concentrates conforming to Annex B shall be tested for conformance with the appropriate
requirements given in other clauses and subclauses of this document after freezing and thawing in
accordance with A.2.1.
3
© ISO 2022 – All rights reserved

---------------------- Page: 9 ----------------------
ISO 7203-4:2022(E)
6 Sediment in the foam concentrate
6.1 Sediment before ageing
Any sediment in the concentrate sampled in accordance with A.1 shall be dispersible through a 180 µm
sieve. The percentage volume of the sediment shall be not more than 0,25 % when tested in accordance
with Annex C.
6.2 Sediment after ageing
Any sediment in the concentrate aged in accordance with B.2 shall be dispersible through a 180 µm
sieve. The percentage volume of sediment shall be not more than 1,0 % when tested in accordance with
Annex C.
7 Determination of viscosity
7.1 Newtonian foam concentrates
The viscosity of the foam concentrate at the lowest temperature for use claimed by the manufacturer
2 −1
shall be determined in accordance with ISO 3104. If the viscosity is > 200 mm s , the container shall be
marked: “This concentrate can require special proportioning equipment”.
7.2 Pseudo-plastic foam concentrates
The viscosity of the foam concentrate shall be determined in accordance with Annex D. If the viscosity
−1
at the lowest temperature for use is greater than or equal to 120 mPa·s at 375 s , the container shall be
marked: “This concentrate can require special proportioning equipment.”
NOTE Pseudo-plastic foam concentrates are a particular class of non-Newtonian foam concentrate and have
a viscosity that decreases with increasing shear rate at constant temperature.
8 pH of the foam concentrate
8.1 pH limits
The pH of the foam concentrate, before and after temperature conditioning in accordance with A.2,
shall be not less than 6,0 and not more than 8,5 at (20 ± 2) °C.
8.2 Sensitivity to temperature
The difference in pH between before and after temperature conditioning shall not be greater than
1,0 pH units.
9 Surface tension of the foam solution
9.1 Before temperature conditioning
The surface tension of the foam solution prepared from the concentrate, before temperature
conditioning in accordance with A.2 at the supplier’s recommended concentration, shall be within
±10 % of the characteristic value when determined in accordance with E.2.
4
  © ISO 2022 – All rights reserved

---------------------- Page: 10 ----------------------
ISO 7203-4:2022(E)
9.2 Temperature sensitivity
The surface tension of the foam solution prepared from the concentrate, after temperature conditioning
in accordance with A.2 at the supplier’s recommended concentration, shall be determined in accordance
with E.2.
The value obtained after temperature conditioning shall not be less than 0,95 times or more than
1,05 times the value obtained before temperature conditioning.
10 Expansion and drainage of foam
10.1 Expansion
10.1.1 Limits
The difference between the expansion of the foam produced from the foam concentrate, before and
after temperature conditioning in accordance with A.2, with potable water and, if appropriate, with
synthetic sea water in accordance with F.4, and the characteristic value shall be within either ±20 %
of the characteristic value or ±1,0 of the characteristic value, whichever is the greater, when tested in
accordance with Annex F.
10.2 Drainage
10.2.1 Limits
The difference between the drainage time of the foam produced from the foam concentrate, before and
after temperature conditioning in accordance with A.2, with potable water and, if appropriate, with
synthetic sea water in accordance with F.4, and the characteristic value shall be within ±20 % of the
characteristic value when tested in accordance with Annex F.
11 Test fire performance
Class A foam concentrate shall extinguish a wood crib fire according to G.1.1 and pass the test for
extinguishment of deep-seated fires according to G.1.2.
12 Corrosion
Where used in aircraft or other applications involving corrosion-sensitive technologies, it is
recommended to conduct appropriate corrosion tests and provide the information to end users.
13 Toxicology and environmental information
Manufacturers of concentrates shall provide information about the toxicological and ecotoxicological
impact of their product at its highest recommended concentration in accordance with Annex H.
14 Marking, packaging and specification sheet
14.1 Marking
14.1.1 The following information shall be marked on the shipping container:
a) designation (identifying name) of the concentrate and the words “Class A foam concentrate”;
b) recommended usage concentration for use (most commonly 1 %, 3 % or 6 %);
5
© ISO 2022 – All rights reserved

---------------------- Page: 11 ----------------------
ISO 7203-4:2022(E)
c) any tendency of the foam concentrate to cause harmful physical effects, the methods required to
avoid them and the first aid treatment if they occur;
d) recommended storage temperature and temperature of use;
e) if the concentrate conforms with Clause 5, it shall be marked with the words “Not affected by
freezing and thawing” or, if the foam concentrate does not conform with Clause 5, the words “Do
not freeze”;
f) nominal quantity in the container;
g) supplier’s name and address;
h) batch number;
i) the words “Not suitable for use with sea water” or “Suitable for use with sea water”, as appropriate.
WARNING — It is extremely important that the foam concentrate, after dilution with water to the
recommended concentration and in normal usage, does not present a significant toxic hazard to
life in relation to the environment.
14.1.2 Markings on shipping containers shall be permanent and legible.
14.1.3 Non-Newtonian concentrates should be appropriately identified.
14.1.4 Foam concentrates in accordance with ISO 7203-1 shall also be marked “low-expansion”.
14.1.5 Foam concentrates in accordance with ISO 7203-2 shall also be marked “medium-expansion” or
“high-expansion” or both.
14.1.6 Foam concentrates in accordance with ISO 7203-3 shall also be marked “alcohol resistant”.
14.2 Packaging
The packaging of the foam concentrate shall ensure that the essential characteristics of the concentrate
are preserved when stored and handled in accordance with the supplier's recommendations.
14.3 Specification sheet
14.3.1 If requested by the user, the supplier shall provide a list of the characteristic values.
14.3.2 If the foam concentrate is Newtonian and the viscosity at the lowest temperature for use is
2
more than 200 mm /s when measured in accordance with ISO 3104, it shall be marked with the words
“This concentrate can require special proportioning equipment.”.
14.3.3 If the foam concentrate is pseudo-plastic and the viscosity at the lowest temperature for use is
−1
greater than or equal to 120 mPa·s at 375 s , it shall be marked with the words “Pseudo-plastic foam
concentrate. This concentrate can require special proportioning equipment.”.
14.3.4 Non-Newtonian concentrates should be appropriately identified.
6
  © ISO 2022 – All rights reserved

---------------------- Page: 12 ----------------------
ISO 7203-4:2022(E)
Annex A
(normative)

Preliminary sampling and conditioning of the foam concentrate
A.1 Preliminary sampling
The sampling method shall ensure representative samples, whether taken from a bulk container or a
number of individual packages.
Store samples in tightly closed containers.
NOTE Containers of capacity 20 l are suitable.
A.2 Conditioning of foam concentrate
A.2.1 If the supplier claims that the concentrate is not adversely affected by freezing and thawing,
condition the concentrate sample through four cycles of freezing and thawing, generally as described in
B.2, before conditioning in accordance with A.2.2.
If the foam concentrate is adversely affected by freezing and thawing, it is conditioned in accordance
with A.2.2 without prior freezing and thawing.
A.2.2 Condition the concentrate in the sealed container for 7 days at (60 ± 2) °C, followed by 1 day at
(20 ± 5) °C.
A.3 Subsequent testing
Test samples shall be prepared in accordance with A.1, or A.2.1 and A.2.2 as appropriate. Shake the
sample container before sampling for further tests.
7
© ISO 2022 – All rights reserved

---------------------- Page: 13 ----------------------
ISO 7203-4:2022(E)
Annex B
(normative)

Determination of tolerance to freezing and thawing
B.1 Apparatus
The usual laboratory apparatus and, in particular, the following.
B.1.1 Freezing chamber, capable of achieving the temperatures required in B.2.
B.1.2 Tube, polyethylene, approximately 10 mm in diameter, approximately 400 mm long and sealed
and weighted at one end, with suitable spacers attached; see Figure B.1 for a typical form.
B.1.3 Measuring cylinder, glass, of capacity 500 ml, approximately 400 mm high and approximately
65 mm in diameter, with a stopper.
B.2 Procedure
Set the temperature of the freezing chamber (B.1.1) to at least 10 °C below the freezing point of the
sample measured in accordance with EN 1568-3:2018, Annex K.
To prevent the glass measuring cylinder (B.1.3) from breaking due to expansion of the foam concentrate
upon freezing, insert the tube (B.1.2) into the measuring cylinder with the sealed end downward,
weighted if necessary to avoid flotation, with the spacers to ensure that it remains approximately on
the central axis of the cylinder. Fill the cylinder and fit the stopper.
Place the cylinder in the freezing chamber, cool it and maintain at the required temperature for 24 h.
At the end of this period, thaw the sample for not less than 24 h and not more than 96 h in an ambient
temperature of (20 ± 5) °C.
Repeat three times to give four cycles of freezing and thawing before testing.
Examine the sample for stratification and non-homogeneity.
8

...