Foreword

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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 document 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).

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This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 4, Burning behaviour, in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 249, Plastics, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

This first edition of ISO 5659 cancels and replaces ISO 5659-2:2017, which has been technically revised.

The main changes are as follows:

Annex G has been added as background information.

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.

Introduction

Fire is a complex phenomenon; its development and effects depend upon a number of interrelated factors. The behaviour of materials and products depends upon the characteristics of the fire, the method of use of the materials and the environment in which they are exposed to (see also ISO/TS 3814^[1^] and ISO 13943).

A test such as is specified in this document deals only with a simple representation of a particular aspect of the potential fire situation, typified by a radiant heat source, and it cannot alone provide any direct guidance on behaviour or safety in fire. A test of this type may, however, be used for comparative purposes or to ensure the existence of a certain quality of performance (in this case, smoke production) considered to have a bearing on fire behaviour generally. It would be wrong to attach any other meaning to results from this test.

The term “smoke” is defined in ISO 13943 as a visible suspension of solid and/or liquid particles in gases resulting from incomplete combustion. It is one of the first response characteristics to be manifested and should almost always be taken into account in any assessment of fire hazard as it represents one of the greatest threats to occupants of a building or other enclosure, such as a ship or train, on fire.

The responsibility for the preparation of ISO 5659 was transferred during 1987 from ISO/TC 92 to ISO/TC 61 on the understanding that the scope and applicability of the standard for the testing of materials should not be restricted to plastics but should also be relevant to other materials where possible, including building materials. See Annex G for further information.

1 Scope

This document specifies a method of measuring smoke production from the exposed surface of specimens of materials or composites. It is applicable to specimens that have an essentially flat surface and do not exceed 25 mm in thickness when placed in a horizontal orientation and subjected to specified levels of thermal irradiance in a closed cabinet with or without the application of a pilot flame. This method of test is applicable to all plastics.

It is intended that the values of optical density determined by this test be taken as specific to the specimen or assembly material in the form and thickness tested and are not to be considered inherent, fundamental properties.

The test is intended primarily for use in research and development and fire safety engineering in buildings, trains, ships, etc. and not as a basis for ratings for building codes or other purposes. No basis is provided for predicting the density of smoke that can be generated by the materials upon exposure to heat and flame under other (actual) exposure conditions. This test procedure excludes the effect of irritants on the eye.

NOTE This test procedure addresses the loss of visibility due to smoke density, which generally is not related to irritancy potency (see Annex E).

It is emphasized that smoke production from a material varies according to the irradiance level to which the specimen is exposed. The results yielded from the method specified in this document are based on exposure to the specific irradiance levels of 25 kW/m² and 50 kW/m².

2 Normative references

3 Terms and definitions

4 Principles of the test

5 Suitability of a material or product for testing

5.1 Material or product geometry

5.2 Surface characteristics

5.3 Asymmetrical products

6 Specimen construction and preparation

6.1 Number of specimens

6.2 Size of specimens

6.3 Specimen preparation

6.4 Conditioning

6.5 Wrapping of specimens

6.6 Dimensionally unstable materials

7 Apparatus and ancillary equipment

7.1 General

7.2 Test chamber

7.3 Specimen support and heating arrangements

7.4 Gas supply

7.5 Photometric system

7.6 Chamber leakage

7.7 Cleaning materials

7.8 Ancillary equipment

8 Test environment

8.1

8.2

9 Setting-up and calibration procedures

9.1 General

9.2 Alignment of photometric system

9.3 Selection of compensating filter(s)

9.4 Linearity check

9.5 Calibration of range-extension filter

9.6 Chamber leakage rate test

9.7 Burner calibration

9.8 Radiator cone calibration

9.9 Cleaning

9.10 Frequency of checking and calibrating procedure

10 Test procedure

10.1 General

10.2 Preparation of test chamber

10.3 Tests with pilot flame

10.4 Preparation of the photometric system

10.5 Loading the specimen

10.6 Recording of light transmission

10.7 Observations

10.8 Termination of test

10.9 Testing in different modes

11 Expression of results

11.1 Specific optical density, D_s

11.2 Clear-beam correction factor, D_c

12 Precision

13 Test report

Bibliography

ISO 5659:2026

Plastics. Smoke generation. Determination of optical density by a single-chamber test

Current

Published:

27 Jan 2026