GB/T 8625-2026 Test method of difficult-flammability for building material English, Anglais, Englisch, Inglés, えいご
This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation, self-check, revision and verification) will be delivered upon being ordered.
ICS
CCS
National Standard of the People's Republic of China
GB/T 8625-2026
Replaces GB/T 8625-2005
Test method of difficult-flammability for building material
建筑材料难燃性试验方法
Issue date: 2026-03-31 Implementation date: 2026-10-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
1 Scope
2 Normative References
3 Terms and Definitions
4 Test Apparatus
5 Calibration of the Test Apparatus
6 Test Specimens
7 Conditioning
8 Test Procedure
9 Expression of Test Results
10 Judgement Criteria
11 Test Report
Annex A (Informative) Calorimetric Device
Bibliography
Test method for difficult flammability of building materials
WARNING — It is essential that personnel using this document have practical experience in laboratory work. This document does not purport to address all possible safety concerns. It is the responsibility of the user to take appropriate safety and health measures.
1 Scope
This document describes a test method for determining the residual length of combustion and the flue gas temperature of building materials using a vertical combustion furnace.
This document applies to the determination of the combustion performance of building materials used in industrial and civil buildings. The determination of the combustion performance of materials used in other locations may refer to this document.
2 Normative References
The following documents are essential for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 5907.1 Fire protection vocabulary — Part 1: General terms
GB/T 16839.1 Thermocouples — Part 1: EMF specifications and tolerances
GB/T 40238 Building materials and products — Substrate selection, conditioning and installation requirements for fire tests
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 5907.1 and the following apply.
3.1 afterflame
Persistence of flaming after the removal of the ignition source.
[Source: ISO 13943:2023, 3.12]
3.2 afterglow
Persistence of glowing in the combustion zone after the removal of the ignition source and after the cessation of any flaming.
[Source: ISO 13943:2023, 3.14, modified]
3.3 smouldering
Slow combustion of a material without visible light.
NOTE: Usually manifested by the generation of smoke and an increase in temperature.
[Source: GB/T 5907.1-2014, 2.28, modified]
4 Test Apparatus
4.1 Vertical combustion furnace
4.1.1 General
The vertical combustion furnace consists of a combustion chamber, a burner, a specimen holder, an airflow stabilisation layer and a flue. Its external dimensions are (1000 ± 40) mm × (1000 ± 40) mm × (3930 ± 40) mm, see Figures 1 and 2.
4.1.2 Combustion chamber
The combustion chamber is composed of furnace walls and furnace doors. The internal dimensions of the combustion chamber are (800 ± 20) mm × (800 ± 20) mm × (2000 ± 20) mm. The furnace wall is of a thermal insulation sandwich structure, consisting from inside to outside of a 2 mm thick stainless steel plate, a (6 ± 2) mm thick refractory fibre felt, two layers of rock wool insulation material each of (40 ± 3) mm single thickness, a (10 ± 2) mm thick calcium silicate board, and a 2 mm thick stainless steel plate.
The furnace doors are divided into an upper door and a lower door, each connected to the furnace body by hinges. The door construction is the same as that of the furnace wall (see Figure 2). The two doors are pressed tightly against the furnace body by handwheels and fixing screws.
Observation windows are provided on both the upper furnace door and the rear wall of the combustion chamber.
4.1.3 Burner
The burner (see Figure 3) is a square structure of dimensions (200 ± 2) mm × (200 ± 2) mm. Eight stainless steel nozzles with a diameter of (3.5 ± 0.1) mm are installed on each of the four side tubes. The upper edges of all nozzles shall lie in the same horizontal plane, with a horizontal deviation not exceeding ±0.5 mm. The burner shall be installed horizontally at the centre of the combustion chamber, (1000 ± 10) mm above the furnace floor. The burner uses a gas mixture of methane, with a purity of not less than 99% methane, and air. Using volumetric flow meters, under standard conditions (0 °C, 101.325 kPa), the volumetric flow rate of methane is (35.0 ± 0.5) L/min, and the volumetric flow rate of air is (17.5 ± 0.2) L/min. Using mass flow controllers, under standard conditions (density of methane 0.717 g/L, density of air 1.293 g/L), the mass flow rate of methane is (418 ± 6) mg/s, and the mass flow rate of air is (378 ± 4) mg/s.
When volumetric flow meters are used, before the test, the ambient atmospheric pressure under actual conditions, the inlet pressures of methane and of compressed air entering the flow meters, and the temperatures of the methane and of the compressed air shall be measured to determine the flow rates of methane and air under actual operating conditions. The temperatures of the methane and of the compressed air shall be measured using sheathed insulated K type thermocouples with a wire diameter of 0.5 mm and an outer diameter not greater than 3 mm, the same as the external diameter. The tolerance class of the thermocouples shall comply with Class 2 requirements of GB/T 16839.1. Thermocouples shall be installed on the gas supply pipes near the flow meters, and insulation material with a thickness of not less than 25 mm shall be wrapped around the gas supply pipes on both the upstream and downstream sides of the installation position, each over a length of (100 ± 10) mm.
Before the test, with the burner ignited and the furnace doors closed, the flow rates of methane and of air under actual operating conditions shall be calculated using formula (1).
4.1.4 Specimen holder
The specimen holder adopts a rectangular cuboid frame structure (see Figure 4). The frame is welded from angle steel ∠25×25×3, with a height of (1000 ± 5) mm. Steel plates are fitted on each of the four sides of the frame, two plates per side. The dimensions of a single steel plate are: length (380 ± 10) mm, width (40 ± 5) mm, thickness 3 mm. The lower steel plates are located (345 ± 10) mm above the bottom of the frame, and the upper steel plates are located (760 ± 10) mm above the bottom of the frame. Two adjusting screws are fitted on each steel plate to adjust the mounting distance of the specimen. On two opposite sides of the frame, two steel tubes are placed horizontally (30 ± 5) mm below the upper steel plates. The length of each steel tube is (150 ± 20) mm, and the external diameter is (20 ± 10) mm.
4.1.5 Airflow stabilisation layer
The airflow stabilisation layer is a frame made of angle steel, placed horizontally directly below the burner, see Figure 2. A wire mesh is laid on the bottom of the frame, and multiple layers of glass fibre felt are laid on the wire mesh. To form a uniform airflow within the combustion chamber, air is introduced into the lower part of the furnace through a pipe of diameter (200 ± 10) mm. The introduced air shall be maintained at a constant temperature and flow rate.
4.1.6 Flue
The flue of the vertical combustion furnace is a square duct with a cross sectional area of (500 ± 10) mm × (500 ± 10) mm. The lower part of the flue communicates with the combustion chamber, and the upper part connects to the exhaust system.
4.2 Exhaust system
The exhaust system is connected to the flue. To maintain a negative pressure within the vertical combustion furnace throughout the entire test procedure, the exhaust power of the exhaust system shall be adjustable.
4.3 Measuring instruments
4.3.1 Flow meters
4.3.1.1 Mass flow controllers or volumetric flow meters shall be used to control the flow rates of methane and compressed air. If mass flow controllers are used, the measuring range for methane shall be at least 0 mg/s to 520 mg/s, and for air at least 0 mg/s to 470 mg/s, with a reading accuracy of 2%. If volumetric flow meters are used, for methane, the maximum measured value of the flow meter shall not be less than 40 L/min; for air, not less than 20 L/min. The accuracy class shall not be lower than Class 2.5.
4.3.1.2 An orifice plate flow meter, a bidirectional pressure probe or a rotating vane anemometer shall be used to measure the flow rate of air introduced into the vertical combustion furnace. The flow measurement device shall be installed in a straight section of the gas supply pipe with a smooth internal surface, and the length of the straight pipe on both sides of the device shall not be less than five times the internal diameter of the pipe. The measurement accuracy of the flow rate shall not be less than 0.4 m³/min.
4.3.2 Thermocouples
4.3.2.1 Sheathed insulated K type thermocouples, conforming to Class 2 tolerance requirements of GB/T 16839.1, shall be used to measure the flue gas temperature and the furnace wall temperature. The thermocouple wire diameter shall be 0.5 mm, and the external diameter shall not exceed 3 mm.
Standard
GB/T 8625-2026 Test method of difficult-flammability for building material (English Version)
Standard No.
GB/T 8625-2026
Status
to be valid
Language
English
File Format
PDF
Word Count
10500 words
Price(USD)
315.0
Implemented on
2026-10-1
Delivery
via email in 1~5 business day
Detail of GB/T 8625-2026
Standard No.
GB/T 8625-2026
English Name
Test method of difficult-flammability for building material
GB/T 8625-2026 Test method of difficult-flammability for building material English, Anglais, Englisch, Inglés, えいご
This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation, self-check, revision and verification) will be delivered upon being ordered.
ICS
CCS
National Standard of the People's Republic of China
GB/T 8625-2026
Replaces GB/T 8625-2005
Test method of difficult-flammability for building material
建筑材料难燃性试验方法
Issue date: 2026-03-31 Implementation date: 2026-10-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
1 Scope
2 Normative References
3 Terms and Definitions
4 Test Apparatus
5 Calibration of the Test Apparatus
6 Test Specimens
7 Conditioning
8 Test Procedure
9 Expression of Test Results
10 Judgement Criteria
11 Test Report
Annex A (Informative) Calorimetric Device
Bibliography
Test method for difficult flammability of building materials
WARNING — It is essential that personnel using this document have practical experience in laboratory work. This document does not purport to address all possible safety concerns. It is the responsibility of the user to take appropriate safety and health measures.
1 Scope
This document describes a test method for determining the residual length of combustion and the flue gas temperature of building materials using a vertical combustion furnace.
This document applies to the determination of the combustion performance of building materials used in industrial and civil buildings. The determination of the combustion performance of materials used in other locations may refer to this document.
2 Normative References
The following documents are essential for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 5907.1 Fire protection vocabulary — Part 1: General terms
GB/T 16839.1 Thermocouples — Part 1: EMF specifications and tolerances
GB/T 40238 Building materials and products — Substrate selection, conditioning and installation requirements for fire tests
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 5907.1 and the following apply.
3.1 afterflame
Persistence of flaming after the removal of the ignition source.
[Source: ISO 13943:2023, 3.12]
3.2 afterglow
Persistence of glowing in the combustion zone after the removal of the ignition source and after the cessation of any flaming.
[Source: ISO 13943:2023, 3.14, modified]
3.3 smouldering
Slow combustion of a material without visible light.
NOTE: Usually manifested by the generation of smoke and an increase in temperature.
[Source: GB/T 5907.1-2014, 2.28, modified]
4 Test Apparatus
4.1 Vertical combustion furnace
4.1.1 General
The vertical combustion furnace consists of a combustion chamber, a burner, a specimen holder, an airflow stabilisation layer and a flue. Its external dimensions are (1000 ± 40) mm × (1000 ± 40) mm × (3930 ± 40) mm, see Figures 1 and 2.
4.1.2 Combustion chamber
The combustion chamber is composed of furnace walls and furnace doors. The internal dimensions of the combustion chamber are (800 ± 20) mm × (800 ± 20) mm × (2000 ± 20) mm. The furnace wall is of a thermal insulation sandwich structure, consisting from inside to outside of a 2 mm thick stainless steel plate, a (6 ± 2) mm thick refractory fibre felt, two layers of rock wool insulation material each of (40 ± 3) mm single thickness, a (10 ± 2) mm thick calcium silicate board, and a 2 mm thick stainless steel plate.
The furnace doors are divided into an upper door and a lower door, each connected to the furnace body by hinges. The door construction is the same as that of the furnace wall (see Figure 2). The two doors are pressed tightly against the furnace body by handwheels and fixing screws.
Observation windows are provided on both the upper furnace door and the rear wall of the combustion chamber.
4.1.3 Burner
The burner (see Figure 3) is a square structure of dimensions (200 ± 2) mm × (200 ± 2) mm. Eight stainless steel nozzles with a diameter of (3.5 ± 0.1) mm are installed on each of the four side tubes. The upper edges of all nozzles shall lie in the same horizontal plane, with a horizontal deviation not exceeding ±0.5 mm. The burner shall be installed horizontally at the centre of the combustion chamber, (1000 ± 10) mm above the furnace floor. The burner uses a gas mixture of methane, with a purity of not less than 99% methane, and air. Using volumetric flow meters, under standard conditions (0 °C, 101.325 kPa), the volumetric flow rate of methane is (35.0 ± 0.5) L/min, and the volumetric flow rate of air is (17.5 ± 0.2) L/min. Using mass flow controllers, under standard conditions (density of methane 0.717 g/L, density of air 1.293 g/L), the mass flow rate of methane is (418 ± 6) mg/s, and the mass flow rate of air is (378 ± 4) mg/s.
When volumetric flow meters are used, before the test, the ambient atmospheric pressure under actual conditions, the inlet pressures of methane and of compressed air entering the flow meters, and the temperatures of the methane and of the compressed air shall be measured to determine the flow rates of methane and air under actual operating conditions. The temperatures of the methane and of the compressed air shall be measured using sheathed insulated K type thermocouples with a wire diameter of 0.5 mm and an outer diameter not greater than 3 mm, the same as the external diameter. The tolerance class of the thermocouples shall comply with Class 2 requirements of GB/T 16839.1. Thermocouples shall be installed on the gas supply pipes near the flow meters, and insulation material with a thickness of not less than 25 mm shall be wrapped around the gas supply pipes on both the upstream and downstream sides of the installation position, each over a length of (100 ± 10) mm.
Before the test, with the burner ignited and the furnace doors closed, the flow rates of methane and of air under actual operating conditions shall be calculated using formula (1).
4.1.4 Specimen holder
The specimen holder adopts a rectangular cuboid frame structure (see Figure 4). The frame is welded from angle steel ∠25×25×3, with a height of (1000 ± 5) mm. Steel plates are fitted on each of the four sides of the frame, two plates per side. The dimensions of a single steel plate are: length (380 ± 10) mm, width (40 ± 5) mm, thickness 3 mm. The lower steel plates are located (345 ± 10) mm above the bottom of the frame, and the upper steel plates are located (760 ± 10) mm above the bottom of the frame. Two adjusting screws are fitted on each steel plate to adjust the mounting distance of the specimen. On two opposite sides of the frame, two steel tubes are placed horizontally (30 ± 5) mm below the upper steel plates. The length of each steel tube is (150 ± 20) mm, and the external diameter is (20 ± 10) mm.
4.1.5 Airflow stabilisation layer
The airflow stabilisation layer is a frame made of angle steel, placed horizontally directly below the burner, see Figure 2. A wire mesh is laid on the bottom of the frame, and multiple layers of glass fibre felt are laid on the wire mesh. To form a uniform airflow within the combustion chamber, air is introduced into the lower part of the furnace through a pipe of diameter (200 ± 10) mm. The introduced air shall be maintained at a constant temperature and flow rate.
4.1.6 Flue
The flue of the vertical combustion furnace is a square duct with a cross sectional area of (500 ± 10) mm × (500 ± 10) mm. The lower part of the flue communicates with the combustion chamber, and the upper part connects to the exhaust system.
4.2 Exhaust system
The exhaust system is connected to the flue. To maintain a negative pressure within the vertical combustion furnace throughout the entire test procedure, the exhaust power of the exhaust system shall be adjustable.
4.3 Measuring instruments
4.3.1 Flow meters
4.3.1.1 Mass flow controllers or volumetric flow meters shall be used to control the flow rates of methane and compressed air. If mass flow controllers are used, the measuring range for methane shall be at least 0 mg/s to 520 mg/s, and for air at least 0 mg/s to 470 mg/s, with a reading accuracy of 2%. If volumetric flow meters are used, for methane, the maximum measured value of the flow meter shall not be less than 40 L/min; for air, not less than 20 L/min. The accuracy class shall not be lower than Class 2.5.
4.3.1.2 An orifice plate flow meter, a bidirectional pressure probe or a rotating vane anemometer shall be used to measure the flow rate of air introduced into the vertical combustion furnace. The flow measurement device shall be installed in a straight section of the gas supply pipe with a smooth internal surface, and the length of the straight pipe on both sides of the device shall not be less than five times the internal diameter of the pipe. The measurement accuracy of the flow rate shall not be less than 0.4 m³/min.
4.3.2 Thermocouples
4.3.2.1 Sheathed insulated K type thermocouples, conforming to Class 2 tolerance requirements of GB/T 16839.1, shall be used to measure the flue gas temperature and the furnace wall temperature. The thermocouple wire diameter shall be 0.5 mm, and the external diameter shall not exceed 3 mm.
