ISO 7240-31:2022

Fire detection and alarm systems - Part 31: Resettable line-type heat detectors

This document applies to resettable line-type heat detectors consisting of a sensing element distributed either continuously or discretely at close intervals along its length and connected to a sensor control unit, either directly or through an interface module, intended for use in fire detection and fire alarm systems installed in and around buildings and other civil engineering works. Examples of such technology are an optical fibre, a pneumatic tube, or an electrical sensor cable This document specifies the requirements and performance criteria, the corresponding test methods, and provides for the assessment. This document also covers resettable line-type heat detectors intended for use in the local protection of plants and equipment. This document does not cover non-resettable line-type heat detectors that can only respond once and are based on fixed temperature electrical cables.

Systèmes de détection et d'alarme incendie — Partie 31: Détecteurs de chaleur en ligne resetable

General Information

• Status: Published
• Publication Date: 05-Sep-2022
• ICS: 13.220.20 - Fire protection
• Technical Committee: ISO/TC 21/SC 3 - Fire detection and alarm systems
• Drafting Committee: ISO/TC 21/SC 3/WG 27 - Line-type heat detectors
• Current Stage: 6060 - International Standard published
• Start Date: 06-Sep-2022
• Due Date: 28-May-2022
• Completion Date: 06-Sep-2022

Overview

ISO 7240-31:2022 specifies requirements, performance criteria and test methods for resettable line‑type heat detectors used in fire detection and alarm systems. It applies to detectors where a sensing element is distributed continuously or at short intervals along its length (examples: optical fibre, pneumatic tube, electrical sensor cable) and is connected to a sensor control unit directly or via an interface. The standard covers factory and on‑site assessment, endurance and environmental performance, and also addresses use for local protection of plant and equipment. It explicitly excludes non‑resettable, single‑use fixed‑temperature electrical cables.

Key topics and technical requirements

• Conformance & heat response classes: Defines how detectors are classified by heat response and the conditions for declaring conformity.
• Alarm indication & signalling: Requirements for individual alarm reporting and signalling to control equipment.
• Performance repeatability and reproducibility: Tests and acceptance criteria to ensure consistent operation across units and over time.
• Sensing element behaviour: Fault detection, continuity, and on‑site adjustment of response characteristics.
• Software and interfaces: Requirements for software design, storage of programs/data, and interface modules.
• Environmental & mechanical tests: Procedures for maximum ambient temperature, dry/cold/damp heat, vibration, shock, impact, and corrosion (e.g., SO2) for both sensing elements and control units.
• Electrical resilience: Tests for supply variation, low voltage fault and electromagnetic immunity.
• Fire sensitivity & response: Fire test room methods, static response temperature tests, and response time measurements from application temperatures.
• Test methods and mounting: Detailed test atmospheres, mounting arrangements, tolerances and measurement procedures.

Applications and who uses this standard

• Manufacturers of resettable line‑type heat detectors and sensor control units - for product design, type testing and technical documentation.
• Test laboratories and conformity assessment bodies - to perform the specified environmental, electrical and fire sensitivity tests.
• System integrators and fire safety engineers - to select appropriate detector types and ensure correct installation, interface and alarm behaviour in buildings and industrial sites.
• Building owners, plant operators and regulators - for specifying performance requirements in procurement and compliance with fire safety regulations.

Practical applications include continuous linear detection along cable runs, tunnel and conveyor protection, plant/equipment local protection, and environments where a distributed sensing element (optical fibre, pneumatic tube or electrical cable) is preferred.

Related standards

• Other parts of the ISO 7240 series addressing detectors, control and indicating equipment, and test procedures for fire detection and alarm systems.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 7240-31
First edition
2022-09
Fire detection and alarm systems —
Part 31:
Resettable line-type heat detectors
Systèmes de détection et d'alarme incendie —
Partie 31: Détecteurs de chaleur en ligne resetable
Reference number
© 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: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .viii
Introduction .ix
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 3
4.1 General . 3
4.1.1 Conformance . 3
4.1.2 Heat response classes . 3
4.2 Individual alarm indication . 5
4.3 Signalling . 5
4.4 Repeatability . 6
4.5 Reproducibility . 6
4.6 Connection of ancillary devices. 6
4.7 Manufacturer's adjustments . 6
4.8 Software . 6
4.8.1 General . 6
4.8.2 Software design . 6
4.8.3 The storage of programs and data . 6
4.9 Sensing element fault . 7
4.10 On-site adjustment of response behaviour . 7
4.11 Maximum ambient temperature test (sensing element) . 7
4.12 Variation in supply parameters . 7
4.13 Low voltage fault. 7
4.14 Fire sensitivity for Class A and ror-only RLTHD . 7
4.15 Static response temperature test . 7
4.16 Response times from typical application temperature for ror-only RLTHD . 8
4.17 Dry heat (operational) sensor control unit . 8
4.18 Dry heat (endurance) for sensor control unit and sensing element . 8
4.19 Cold (operational) for sensing element . 8
4.20 Cold (operational) for sensor control unit . 8
4.21 Damp heat, steady-state (endurance) for sensor control unit and sensing element . 8
4.22 Damp heat, cyclic (operational) for sensing element . 8
4.23 Damp heat, cyclic (operational) for sensor control unit . 8
4.24 Damp heat, steady-state (operational) for sensor control unit . 8
4.25 Damp heat, cyclic (endurance) for sensor control unit and sensing element . 8
4.26 Shock (operational) for sensor control unit . 8
4.27 Impact (operational) for sensor control unit . 9
4.28 Impact (operational) for sensing element . 9
4.29 Vibration, sinusoidal (operational) for sensor control unit . 9
4.30 Vibration, sinusoidal (operational) for sensing element . 9
4.31 Vibration, sinusoidal (endurance) for sensor control unit . 9
4.32 Vibration, sinusoidal (endurance) for sensing element . 9
4.33 Sulfur dioxide (SO ) corrosion (endurance) for sensing element . 9
4.34 Sulfur dioxide (SO ) corrosion (endurance) for sensor control unit . 9
4.35 Electromagnetic immunity . 9
5 Test methods . 9
5.1 General . 9
5.1.1 Atmospheric conditions for tests. 9
5.1.2 Operating conditions for tests. 10
5.1.3 Mounting arrangements . 10
5.1.4 Tolerances . 10
iii
5.1.5 Procedure for measurement of response time . 10
5.1.6 Provision for tests . 11
5.1.7 Test schedule . 12
5.2 Individual alarm indication . 14
5.3 Signalling . 14
5.4 Repeatability . 14
5.4.1 Object of the test . 14
5.4.2 Test procedure. 14
5.4.3 Requirements . 15
5.5 Reproducibility . .15
5.5.1 Object of the test . 15
5.5.2 Test procedure. 15
5.5.3 Requirements .15
5.6 Connection of ancillary devices. 15
5.7 Manufacturer's adjustments .15
5.8 Requirements for software-controlled detectors . 15
5.9 Sensing element fault . 15
5.9.1 Object of the test . 15
5.9.2 Sensing element operational continuity . 16
5.9.3 Requirements . 16
5.10 On-site adjustment of response behaviour . 16
5.11 Maximum ambient temperature test (sensing element) . 16
5.11.1 Object of the test . 16
5.11.2 Mounting of the sensing element . 16
5.11.3 Test procedure. 16
5.11.4 Requirements . 16
5.12 Variation in supply parameters . 16
5.12.1 Object of the test . 16
5.12.2 Test procedure. 17
5.12.3 Requirements . 17
5.13 Low voltage fault. 17
5.13.1 Object of the test . 17
5.13.2 Test procedure. 17
5.13.3 Requirements . 17
5.14 Fire sensitivity for Class A and ror-only RLTHD . 17
5.14.1 Object of the test . 17
5.14.2 Principle . 17
5.14.3 Fire test room . 17
5.14.4 Test fires . 18
5.14.5 Mounting of the specimens . 18
5.14.6 Initial conditions . 18
5.14.7 Recording of the fire parameters and response times . 19
5.14.8 Requirements . 19
5.15 Static response temperature test . 19
5.15.1 Object of the test . 19
5.15.2 Test procedure for non-integrating linear and multipoint RLTHD . 19
5.15.3 Test procedure for integrating linear RLTHD . 21
5.15.4 Requirements .22
5.16 Response times from typical application temperature for ror-only RLTHD .22
5.16.1 Object of the test . 22
5.16.2 Test procedure.22
5.16.3 Requirements .22
5.17 Dry heat (operational) test for sensor control unit. 22
5.17.1 Object of the test . 22
5.17.2 Reference . 22
5.17.3 State of the specimen during conditioning .22
5.17.4 Conditioning . 23
5.17.5 Measurements during conditioning . 23
iv
5.17.6 Final measurements . 23
5.17.7 Requirements .23
5.18 Dry heat (endurance) for sensor control unit and sensing element .23
5.18.1 Object of the test . 23
5.18.2 Principle . 23
5.18.3 Reference . 24
5.18.4 State of the specimen during conditioning . 24
5.18.5 Conditioning . 24
5.18.6 Final measurements . 24
5.18.7 Requirements .25
5.19 Cold (operational) for sensing element . 25
5.19.1 Object of the test . 25
5.19.2 Reference . 25
5.19.3 State of the specimen during conditioning . 25
5.19.4 Conditioning . 25
5.19.5 Measurements during conditioning . 25
5.19.6 Final measurements . 25
5.19.7 Requirements .26
5.20 Cold (operational) for sensor control unit . 26
5.20.1 Object of the test . 26
5.20.2 Reference . 26
5.20.3 State of the specimen during conditioning . 26
5.20.4 Conditioning .26
5.20.5 Measurements during conditioning . 26
5.20.6 Final measurements . 26
5.20.7 Requirements . 27
5.21 Damp heat, steady-state (endurance) for sensor control unit and sensing element . 27
5.21.1 Object of the test . 27
5.21.2 Reference . 27
5.21.3 State of the specimen during conditioning . 27
5.21.4 Conditioning . 27
5.21.5 Final measurements . 27
5.21.6 Requirements . 27
5.22 Damp heat, cyclic (operational) for sensing element .28
5.22.1 Object of the test .28
5.22.2 Principle .28
5.22.3 Reference .28
5.22.4 State of the specimen during conditioning .28
5.22.5 Conditioning .28
5.22.6 Measurements during conditioning .29
5.22.7 Final measurements .29
5.22.8 Requirements .29
5.23 Damp heat, cyclic (operational) for sensor control unit .29
5.23.1 Object of the test .29
5.23.2 Principle . 29
5.23.3 Reference . 29
5.23.4 State of the specimen during conditioning .29
5.23.5 Conditioning .29
5.23.6 Measurements during conditioning .30
5.23.7 Final measurements .30
5.23.8 Requirements .30
5.24 Damp heat, steady-state (operational) for sensor control unit .30
5.24.1 Object of the test . 30
5.24.2 Principle . 30
5.24.3 Reference . 30
5.24.4 State of the specimen during conditioning . 31
5.24.5 Conditioning . 31
5.24.6 Measurements during conditioning . 31
v
5.24.7 Final measurements . 31
5.24.8 Requirements . 31
5.25 Damp heat, cyclic (endurance) for sensor control unit and sensing element . 31
5.25.1 Object of the test . 31
5.25.2 Principle . 32
5.25.3 Reference . 32
5.25.4 State of the specimen during conditioning . 32
5.25.5 Conditioning . 32
5.25.6 Final measurements . 32
5.25.7 Requirements . 32
5.26 Shock (operational) for sensor control unit . 33
5.26.1 Object of the test . 33
5.26.2 Reference . 33
5.26.3 State of the specimen during conditioning . 33
5.26.4 Conditioning . 33
5.26.5 Measurements during conditioning . 33
5.26.6 Final measurements . 33
5.26.7 Requirements .33
5.27 Impact (operational) for sensor control unit .34
5.27.1 Object of the test .34
5.27.2 Reference .34
5.27.3 State of the specimen during conditioning .34
5.27.4 Conditioning .34
5.27.5 Measurements during conditioning .34
5.27.6 Final measurements .34
5.27.7 Requirements .34
5.28 Impact (operational) for sensing element . 35
5.28.1 Object of the test . 35
5.28.2 Test apparatus . 35
5.28.3 State of the specimen(s) during conditioning . 35
5.28.4 Conditioning . 35
5.28.5 Measurements during conditioning . 35
5.28.6 Final measurements . 35
5.28.7 Requirements . 36
5.29 Vibration, sinusoidal (operational) for sensor control unit .36
5.29.1 Object of the test . 36
5.29.2 Reference . 36
5.29.3 State of the specimen during conditioning .36
5.29.4 Conditioning .36
5.29.5 Measurements during conditioning .36
5.29.6 Final measurements . 36
5.29.7 Requirements . 37
5.30 Vibration, sinusoidal (operational) for sensing element . 37
5.30.1 Object of the test . 37
5.30.2 Reference . 37
5.30.3 State of the specimen during conditioning . 37
5.30.4 Conditioning . 37
5.30.5 Measurements during conditioning . 37
5.30.6 Final measurements . 37
5.30.7 Requirements .38
5.31 Vibration, sinusoidal (endurance) for sensor control unit .38
5.31.1 Object of the test .38
5.31.2 Reference .38
5.31.3 State of the specimen during conditioning .38
5.31.4 Conditioning .38
5.31.5 Final measurements .38
5.31.6 Requirements .38
5.32 Vibration, sinusoidal (endurance) for sensing element .39
vi
5.32.1 Object of the test . 39
5.32.2 Reference . 39
5.32.3 State of the specimen during conditioning .39
5.32.4 Conditioning .39
5.32.5 Final measurements . 39
5.32.6 Requirements .39
5.33 Sulfur dioxide (SO ) corrosion (endurance) for sensing element .40
5.33.1 Object of the test .40
5.33.2 Reference .40
5.33.3 State of the specimen during conditioning .40
5.33.4 Conditioning .40
5.33.5 Final measurements .40
5.33.6 Requirements .40
5.34 Sulfur dioxide (SO ) corrosion (endurance) for sensor control unit . 41
5.34.1 Object of the test . 41
5.34.2 Reference . 41
5.34.3 State of the specimen during conditioning . 41
5.34.4 Conditioning . 41
5.34.5 Final measurements . 41
5.34.6 Requirements . 41
5.35 Electromagnetic compatib
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