ISO 5659 Plastics - Smoke Formation

The "ISO 5659 Plastics - Smoke formation" standard published by the International Organization for Standardization (ISO) consists of a number of subsections published under the same title. Namely,

• The standard "ISO 5659-1 Part 1: Guidance on Optical Density Testing" defines optical density and describes the requirements. Part 2 of this international standard describes a static (or cumulative) single-chamber test procedure. Currently, the scope of this guide is limited to the test procedure described in Part 2. If future work expands the scope of the standard to include other smoke tests (e.g., dynamic procedures), the scope of Part 1 will be expanded accordingly.

For the purposes of this standard, the following definitions apply in addition to the terms and definitions given in the “ISO 13943 Fire safety – Glossary” standard:

• Bulk optical density expresses a measure of the degree of opacity of smoke in terms of weight loss of the material under test conditions.
• The optical density of smoke is a measure of its degree of opacity (negative common logarithm of the relative transmittance of light).
• Specific optical density is the optical density multiplied by a factor that depends on the instrument and sample size.
• A fire model is a means of generating fire effluents for evaluation of decomposition or samples under defined conditions to represent known stages of a fire. This term should be distinguished from fire modeling, a term used by the fire science community for the mathematical simulation of fire characteristics.
• A fire scenario is a detailed description of the conditions prevailing at specific stages in a real fire or a full-scale fire simulation.

The purpose of this standard is to provide guidance on the applicability of smoke density measurements described in Part 2 of this standard.

Significant progress has been made in the analysis of fire debris in recent years. It is recognized that the composition of the combustion product mixture depends on the nature of the combustion materials, the prevailing temperatures and ventilation conditions, and, in particular, the access of oxygen to the fire core. A number of factors important for categorizing fire atmospheres and comparing atmospheres between laboratory-scale and full-scale fire studies are listed in the table titled "General classification of actual fire stages according to ISO/TR 9122-1" provided within the standard.

Fire involves a complex and interrelated set of physical and chemical phenomena. Consequently, it is essentially impossible to simulate all aspects of a real fire in a laboratory-scale apparatus. The issue of fire model validation is perhaps the most perplexing technical challenge associated with all fire testing.

After ignition, fire development can occur in different ways depending on environmental conditions and the physical arrangement of the combustible materials. However, a general pattern for fire development can be established in a compartment where the overall temperature-time curve shows three stages.

The first stage is the initial stage of a fire before it becomes a sustained flame, and there is only a slight increase in the fire chamber temperature. Ignition and smoke formation are the primary stages in this stage. The second stage (developing fire) begins with ignition and concludes with an exponential increase in fire chamber temperature. In addition to smoke, flame spread and heat release are the primary hazards in this stage. The third stage (fully developed fire) begins when the surface of all combustible contents of the room has decomposed to such an extent that instantaneous ignition occurs throughout the room, resulting in a rapid and substantial temperature increase (flashover).

By the end of the third stage, the fuels and oxygen have been largely consumed, and therefore the temperature has decreased at a rate that varies depending on the ventilation and the heat and mass transfer characteristics of the system.

At each of these stages, a different mixture of decomposition products may form, influencing the smoke density produced at that stage. Furthermore, knowledge of the fire scenario being considered is necessary, particularly the incident heat flux, oxygen availability, and smoke exhaust facility conditions.

• The standard “ISO 5659-2 Part 2: Determination of optical density by a single-chamber test” describes a method for measuring smoke production from the exposed surface of substantially flat materials, composites or assemblies when placed in a horizontal position and exposed to specified thermal irradiance levels in a closed cabinet with or without the application of a pilot flame.

This test method is applicable to all plastics and can also be used to evaluate other materials (e.g. rubbers, textile coatings, painted surfaces, wood and other materials).

The optical density values ​​determined by this test are intended to be specific to the sample or assembly material in the form and thickness tested and are not intended to be considered intrinsic, fundamental properties. The test is intended primarily for use in research and development of buildings, trains, ships, and similar vehicles, and in fire safety engineering, and is not intended to be used as the basis for ratings for building codes or other purposes.

No basis is provided for estimating the smoke density that would be produced by exposing materials to heat and flame under other (actual) exposure conditions, and no correlation has been established with measurements derived from other test methods. This test procedure excludes the effect of irritating substances on the eye.

This test procedure addresses the loss of visibility caused by smoke density, which is not generally associated with irritating effects, as described in Part 1 of this standard. It is emphasized that smoke emanating from a material varies with the level of radiation to which the specimen is exposed.

In short, this standard was developed to better evaluate the smoke generation potential of materials burning under a wider range of heat flux conditions than alternative single-chamber smoke tests and to allow thermoplastics to be tested in a horizontal position.

• The standard “ISO 5659-3 Part 3: Determination of optical density by the dynamic flow method” describes a method for measuring smoke production from the exposed surfaces of samples consisting of substantially flat materials, composites or assemblies not exceeding 25 mm in thickness, when placed in a horizontal position and subjected to thermal irradiation at specified levels under forced ventilation conditions, with or without the application of a pilot flame.

This test method is applicable to plastics and can also be used to evaluate other materials (e.g., rubbers, textile coatings, painted surfaces, wood, and other building materials). Optical density values ​​determined by this test are specific to the sample or assembly material in the form and thickness tested and should not be considered intrinsic, fundamental properties.

This test method is intended for use in research and development and is not primarily intended as a rating basis for building codes or other purposes. No basis is provided for predicting the smoke density that materials may produce upon exposure to heat and flame under other exposure conditions, such as end-use conditions, and no correlation has been established with measurements derived from other test methods. It is emphasized that smoke from a material varies with ventilation conditions and the irradiance level to which the sample is exposed.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the "ISO 5659 Plastics - Smoke Formation" standard.