ISO 7240-27:2025

International
Standard
ISO 7240-27
Third edition
Fire detection and alarm systems —
2025-04
Part 27:
Point type fire detectors using a
smoke sensor in combination with
a carbon monoxide sensor and,
optionally, one or more heat sensors
Systèmes de détection et d'alarme d'incendie —
Partie 27: Détecteurs ponctuels d'incendie utilisant un capteur de
fumée en combinaison avec un capteur de monoxyde de carbone
(CO) et, optionnellement, un ou plusieurs capteurs de chaleur
Reference number
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ii
Contents Page
Foreword .vii
Introduction .viii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 General requirements . 2
4.1 Conformance .2
4.2 Response threshold value of detectors using scattered or transmitted light .2
4.3 Individual alarm indication .2
4.4 Connection of ancillary devices.3
4.5 Monitoring of detachable detectors . .3
4.6 Manufacturer’s adjustments .3
4.7 On-site adjustment of response behaviour .3
4.8 Protection against the ingress of foreign bodies .3
4.9 Rate-sensitive CO response behaviour .3
4.10 Smoke response to slowly developing fires .4
4.11 Requirements for software-controlled detectors .4
4.11.1 General .4
4.11.2 Software design .4
4.11.3 Storage of programs and data .4
5 Test methods . 5
5.1 General .5
5.1.1 Atmospheric conditions for tests.5
5.1.2 Operating conditions for tests.5
5.1.3 Mounting arrangements .5
5.1.4 Tolerances .5
5.1.5 Measurement of smoke response threshold value .5
5.1.6 Measurement of CO response threshold value .6
5.1.7 Measurement of heat response value .6
5.1.8 Provision for tests .7
5.1.9 Test schedule .7
5.1.10 Test report .9
5.2 Repeatability of smoke response .9
5.2.1 Objective of the test .9
5.2.2 Test procedure.9
5.2.3 Requirements .9
5.3 Repeatability of CO response . .9
5.3.1 Objective of the test .9
5.3.2 Test procedure.9
5.3.3 Requirements .9
5.4 Directional dependence of smoke response .9
5.4.1 Objective of the test .9
5.4.2 Test procedure.10
5.4.3 Requirements .10
5.5 Directional dependence of CO response .10
5.5.1 Objective of the test .10
5.5.2 Test procedure.10
5.5.3 Requirements .10
5.6 Directional dependence of heat response (optional function) .10
5.6.1 Objective of the test .10
5.6.2 Test procedure.10
5.6.3 Requirements .11
5.7 Lower limit of heat response (optional function) .11

iii
5.7.1 Objective of the test .11
5.7.2 Test procedure.11
5.7.3 Requirements .11
5.8 Reproducibility of smoke response .11
5.8.1 Objective of the test .11
5.8.2 Test procedure.11
5.8.3 Requirements . 12
5.9 Reproducibility of CO response . 12
5.9.1 Objective of the test . 12
5.9.2 Test procedure. 12
5.9.3 Requirements . 12
5.10 Reproducibility of heat response (optional function). 12
5.10.1 Objective of the test . 12
5.10.2 Test procedure. 12
5.10.3 Requirements . 12
5.11 Exposure to chemical agents at environmental concentrations . 13
5.11.1 Objective of the test . 13
5.11.2 Test procedure. 13
5.11.3 Requirements . 13
5.12 Long-term stability of CO response .14
5.12.1 Objective of the test .14
5.12.2 Test procedure.14
5.12.3 Requirements .14
5.13 Saturation .14
5.13.1 Objective of the test .14
5.13.2 Test procedure.14
5.13.3 Requirements . 15
5.14 Variation in supply parameters . 15
5.14.1 Objective of the test . 15
5.14.2 Test procedure. 15
5.14.3 Requirements . 15
5.15 Air movement .16
5.15.1 Objective of the test .16
5.15.2 Test procedure.16
5.15.3 Requirements .16
5.16 Dazzling .17
5.16.1 Objective of the test .17
5.16.2 Test procedure.17
5.16.3 Requirements .17
5.17 Dry heat (operational) .17
5.17.1 Objective of the test .17
5.17.2 Test procedure.17
5.17.3 Requirements .18
5.18 Dry heat (endurance) .18
5.18.1 Objective of the test .18
5.18.2 Test procedure.18
5.18.3 Requirements .19
5.19 Cold (operational), smoke .19
5.19.1 Objective of the test .19
5.19.2 Test procedure.19
5.19.3 Requirements .19
5.20 Cold (operational), CO . 20
5.20.1 Objective of the test . 20
5.20.2 Test procedure. 20
5.20.3 Requirements . 20
5.21 Damp heat, cyclic (operational) . 20
5.21.1 Objective of the test . 20
5.21.2 Test procedure.21
5.21.3 Requirements .21

iv
5.22 Damp heat, steady state (operational) . 22
5.22.1 Objective of the test . 22
5.22.2 Test procedure. 22
5.22.3 Requirements . 22
5.23 Damp heat, steady state (endurance) . 23
5.23.1 Objective of the test . 23
5.23.2 Test procedure. 23
5.23.3 Requirements . 23
5.24 Low humidity, steady state (endurance) .24
5.24.1 Objective of the test .24
5.24.2 Test procedure.24
5.24.3 Requirements .24
5.25 Sulfur dioxide SO corrosion (endurance) .24
5.25.1 Objective of the test .24
5.25.2 Test procedure.24
5.25.3 Requirements . 25
5.26 Shock (operational) . 25
5.26.1 Objective of the test . 25
5.26.2 Test procedure. 25
5.26.3 Requirements . 26
5.27 Impact (operational) . 26
5.27.1 Objective of the test . 26
5.27.2 Test procedure. 26
5.27.3 Requirements .27
5.28 Vibration, sinusoidal (operational) .27
5.28.1 Objective of the test .27
5.28.2 Test procedure.27
5.28.3 Requirements . 28
5.29 Vibration, sinusoidal (endurance) . 28
5.29.1 Objective of the test . 28
5.29.2 Test procedure. 29
5.29.3 Requirements . 29
5.30 Electromagnetic compatibility (EMC) immunity tests (operational) . 29
5.30.1 Objective of the test . 29
5.30.2 Test procedure. 30
5.30.3 Requirements . 30
5.31 Fire sensitivity . 30
5.31.1 Objective of the test . 30
5.31.2 Test procedure. 30
5.31.3 Requirements .32
6 Test report .32
7 Marking . .32
8 Data .33
8.1 Hardware documentation . 33
8.2 Software documentation . 33
Annex A (normative) Gas test chamber for CO response threshold value and cross sensitivity
measurements .35
Annex B (normative) Construction of the heat tunnel .36
Annex C (normative) Apparatus for dazzling test .39
Annex D (normative) Apparatus for impact test .40
Annex E (normative) Fire test room .42
Annex F (normative) Smouldering (pyrolysis) wood fire (TF2) .44
Annex G (normative) Glowing smouldering cotton fire (TF3) . 47

v
Annex H (normative) Flaming plastics (polyurethane) fire (TF4) .50
Annex I (normative) Liquid (heptane) fire (TF5) .53
Annex J (normative) Low temperature black smoke (decalene) liquid fire (TF8) .56
Annex K (informative) Information concerning the construction of the gas test chamber .59
Bibliography . 61

vi
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,
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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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
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this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 3, Fire detection and alarm systems.
This third edition cancels and replaces the second edition (ISO 7240-27:2018), which has been technically
revised.
The main changes are as follows:
— the use of the threshold values of Band 1 and Band 2 (introduced in the previous edition) has been
simplified, thereby avoiding unnecessary repetitions.
A list of all parts in the ISO 7240 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.

vii
Introduction
A fire detection and fire alarm system is required to function satisfactorily not only in the event of a fire, but
also during and after exposure to conditions likely to be met in practice, such as corrosion, vibration, direct
impact, indirect shock and electromagnetic interference. The tests specified in this document are intended
to assess the performance of the fire detectors under such conditions.
The performance of multi-sensor point fire detectors that incorporate a smoke sensor, a carbon monoxide
(CO) sensor and, optionally, one or more heat sensors is assessed from results obtained in the tests specified
in this document, This document is not intended to place any restrictions on the design and construction of
such detectors.
Smoke detectors using ionization or optical sensors, and conforming to ISO 7240-7, are well established for
the protection of life and property. Even so, they can respond to stimuli other than smoke and, in some
circumstances, can be prone to false alarms. False alarm rates are usually minimized by careful application,
giving some limitations in use, and occasionally with a reduction in protection provided.
It is generally accepted that fire detectors using carbon monoxide (CO) sensors alone, while suitable for the
detection of smouldering fires involving carbonaceous fuels, can be relatively insensitive to free-burning
fires supported by a plentiful supply of oxygen. This limitation can be largely overcome by the inclusion of
a heat sensor whose output is combined in some way with that of the CO sensor. Performance requirements
for CO fire detectors and for CO and heat detectors can be found in ISO 7240-6 and ISO 7240-8 respectively.
Although the CO and heat detector is capable of responding to free-burning fires, it can still be relatively
insensitive to low-temperature fires that produce large amounts of visible smoke but low concentrations
of CO and little heat. This limitation prevents the CO and heat detector from being a true replacement for a
smoke detector in life safety applications.
Many false alarm sources that affect smoke detectors do not produce CO. It is therefore possible that, by adding
a CO sensor to a smoke detector and combining its output in some way with that of the smoke sensor, the
incidence of false alarms can be reduced. This reduction can be achieved while simultaneously providing the
ability to respond to a broader range of fire types than is possible with either a smoke or CO detector alone.
It is possible to improve the performance even further by adding a heat sensor to assist in the response to
clean-burning, high energy fires. This improvement is seen as secondary to the overall performance and for
this reason the heat sensor is treated as optional for compliance with this document.
This document includes a requirement for smoke detectors that operate on the scattered or transmitted
light principle to be marked with one of two possible nominal response threshold value of Band 1 or Band 2.
This marking provides for a clearer choice of response values so that the risk of unwanted alarms can be
decreased in installations where unfavourable environmental conditions are present.
NOTE For some test fires, smoke detectors that operate on the scattered or transmitted light principle and that
have been factory set to the upper response threshold value band can fall outside one of the classification limits given
in ISO/TR 7240-9.
viii
International Standard ISO 7240-27:2025(en)
Fire detection and alarm systems —
Part 27:
Point type fire detectors using a smoke sensor in combination
with a carbon monoxide sensor and, optionally, one or more
heat sensors
1 Scope
This document specifies requirements, test methods and performance criteria for multi-sensor point fire
detectors that incorporate a smoke sensor, a carbon monoxide (CO) sensor and, optionally, one or more heat
sensors, for use in fire detection and alarm systems installed in buildings (see ISO 7240-1).
This document is not applicable to fire detectors using smoke, CO and, optionally heat sensors, which have
special characteristics, and which have been developed for specific risks. For the testing of other types of
fire detectors using smoke, CO and, optionally, heat sensors working on different principles, this document
can therefore be used only for guidance.
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 209, Wrought aluminium and aluminium alloys — Chemical composition
ISO 7240-1, Fire detection and alarm systems — Part 1: General and definitions
ISO 7240-5, Fire detection and fire alarm systems — Part 5: Point type heat detectors
ISO 7240-7, Fire detection and alarm systems — Part 7: Point-type smoke detectors using scattered light,
transmitted light or ionization
IEC 60068-1, Environmental testing — Part 1: General and guidance
IEC 60068-2-1, Environmental testing — Part 2-1: Tests — Test A: Cold
IEC 60068-2-2, Environmental testing — Part 2-2: Tests — Test B: Dry heat
IEC 60068-2-6, Environmental testing — Part 2-6: Tests — Test Fc: Vibration (sinusoidal)
IEC 60068-2-27, Environmental testing — Part 2-27: Tests — Test Ea and guidance: Shock
IEC 60068-2-30, Environmental testing — Part 2-30: Tests — Test Db: Damp, cyclic (12 h + 12 h cycle)
IEC 60068-2-42, Environmental testing — Part 2-42: Tests — Test Kc: Sulphur dioxide test for contacts and
connections
IEC 60068-2-78, Environmental Testing — Part 2-78: Tests — Test Cab: Damp heat, steady state
IEC 62599-2, Alarm systems — Part 2: Electromagnetic compatibility — Immunity requirements for components
of fire and security alarm systems

3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7240-1 and the following apply.
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
response threshold value
magnitude of the reference parameter at which the detector enters an alarm state when subjected to changes
in the smoke or carbon monoxide concentration or temperature
EXAMPLE Smoke response threshold value, CO response threshold value.
Note 1 to entry: The response threshold value can depend on signal processing in the detector and in the control and
indicating equipment.
4 General requirements
4.1 Conformance
In order to conform to
...