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GB/T 42924.1-2023 English PDF (GBT42924.1-2023)

GB/T 42924.1-2023 English PDF (GBT42924.1-2023)

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GB/T 42924.1-2023: Plastics - Smoke generation - Determination of the corrosivity of fire effluents - Part 1: General concepts and applicability
GB/T 42924.1-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.080.01
CCS G 31
GB/T 42924.1-2023
Plastics - Smoke generation - Determination of the
corrosivity of fire effluents - Part 1: General concepts and
applicability
(ISO 11907-1:2019, MOD)
ISSUED ON: AUGUST 06, 2023
IMPLEMENTED ON: MARCH 01, 2024
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
Introduction ... 5
1 Scope ... 6
2 Normative references ... 6
3 Terms and definitions ... 6
4 Purpose ... 7
5 Combustion scenarios and general factors affecting generation of released products 9
6 Type of fire effluent tests ... 9
7 Applicability of test results ... 11
8 Treatment after exposure of corrosion targets ... 11
Bibliography ... 13
Introduction
Smoke corrosivity refers to the reduction in functionality of a material or product due
to the corrosive effect of smoke. All fire effluents and thermal effects, including the
heat released, are corrosive to a certain extent. Therefore, smoke corrosivity is one of
the important factors when assessing the extent of fire damage and losses. However,
there are many and complex factors that affect the degree of smoke corrosion damage,
which may include the following aspects:
- combustion growth rate, which determines the concentration of the effluent;
- the volume into which the effluent diffuses;
- ventilation conditions of the box, including windows, smoke exhaust vents, and
mechanical ventilation;
- the nature of the combustible materials involved in the fire;
- the nature and composition of the exposed surface;
- exposure time;
- conditions for pyrolysis (heat flow, oxygen) and conditions for combustion;
- specific environmental conditions (temperature and humidity) of the contact
surface;
- effectiveness of active and passive fire protection, fire suppression, and smoke
management systems.
At present, there is no smoke corrosivity determination method related to the plastic
field in China, so it is necessary to develop it to provide technical support for subsequent
related research work. GB/T 42924 aims to provide a method for determining the
corrosivity of fire effluents of plastics and is intended to consist of two parts.
- Part 1: General concepts and applicability. The purpose is to provide guidance on
the applicability of the corrosivity test of fire effluents in GB/T 42924.4, introduce
other existing test methods, and illustrate the differences between acidity,
corrosivity, and toxicity.
- Part 4: Dynamic decomposition method using a conical radiant heater. The purpose
is to provide users with a specific dynamic test method for the corrosivity of fire
effluents.
NOTE: Two other methods, ISO 11907-2 and ISO 11907-3, were used in the past but are no longer
used. The relevant international standards have been abolished.
Plastics - Smoke generation - Determination of the
corrosivity of fire effluents - Part 1: General concepts and
applicability
1 Scope
This document defines terms related to smoke corrosivity, smoke acidity, and smoke
toxicity. It proposes a scenario-based approach to control smoke corrosivity. It describes
the test methods for evaluating smoke corrosivity at laboratory scale. It discusses the
applicability of the tests and post-exposure conditions.
This document applies to the determination of the corrosivity of smoke generated by
combustion of materials.
2 Normative references
The following referenced documents are indispensable for the application 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.
GB/T 16172 Test method for heat release rate of building materials (GB/T 16172-
2007, ISO 5660-1:2002, IDT)
ISO 13943 Fire safety - Vocabulary
3 Terms and definitions
For the purpose of this document, the terms and definitions defined in ISO 13943 and
the following apply.
3.1
smoke corrosivity
The extent to which the functionality of a material or product is reduced due to the
corrosive effects of smoke.
3.2
smoke acidity
- provide guidance on the applicability of fire effluent corrosivity tests in GB/T
42924.4;
- introduce other existing test methods;
- explain the differences between acidity, corrosivity, and toxicity.
The definitions in Clause 3 are provided to avoid confusion between smoke corrosivity,
smoke acidity, and smoke toxicity. Acid gas emissions are sometimes used as an indirect
assessment of smoke corrosivity. This is usually evaluated by dissolving a known
amount of fire effluent in a known volume of water, and then testing the resulting
solution for pH, conductivity, or acid concentration. However, smoke corrosivity is not
exactly equivalent to the above values.
Smoke corrosiveness is related to the fire effluent and the conditions under which it
propagates to the corrosion target. It is also affected by the exposure time and the length
of placement time after exposure. Some fire effluents are alkaline, some are acidic,
some are organic matter, and some are inorganic matter. Often, condensation of water
is a factor that enhances corrosivity. The method specified in GB/T 42924.4 improves
the technology for evaluating the corrosivity of combustion materials.
Smoke acidity is related to the change in pH value of a certain volume of liquid after
exposure to the fire effluent. The acidity of smoke-forming liquids during combustion
is related to the released amount of acid gases (usually hydrogen chloride, hydrogen
bromide and hydrogen fluoride) and organic acids (such as acetic acid or formic acid).
GB/T 17650.2 describes the method for determining the smoke acidity by measuring
the pH value or conductivity of an aqueous solution of combustion products. Usually
about 1 g of material is decomposed in a tube furnace at a temperature of 750 ℃ ~
950 ℃, while air is introduced, and the flue gas generated by combustion is collected
through a cleaning bottle filled with deionized water, and then its pH value and
conductivity are analyzed.
GB/T 17650.1 describes the methods for measuring halogen content in combustion
products. This method is commonly used for cable materials. A sample with a mass of
approximately 0.5 g ~ 1 g is heated in a tube furnace (usually 800 °C). The decomposed
gases are collected and processed through a cleaning bottle containing aqueous sodium
hydroxide solution to absorb all acidic gases. Then use traditional wet chemical
methods (see ISO 19701) to determine the contents of chloride ions, bromide ions, and
fluoride ions. Results are generally expressed in HCl equivalents.
The toxicity and corrosivity of fire effluents are entirely different. Toxicity refers to
adverse effects on living organisms, while corrosivity refers to damage to equipment,
usually caused by damage to metal parts.
NOTE: GB/T 38310 and ISO 13571 give useful information on the toxicity of fire effluents.
products is expressed as a function of the increase in resistance of the corrosion target
within 1 h of exposure to combustion products.
NOTE: The static test method of ISO 11907-2 has been abolished.
6.3 Dynamic decomposition method
6.3.1 General
The dynamic decomposition method is that the sample is burned in an air flow, and the
air flow transports the combustion...
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