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BS 476 Fire Test for Flexible Duct Connectors

In the world of construction and engineering, safety and compliance with fire regulations are of utmost importance. When it comes to ventilation systems, flexible duct connectors play a crucial role in ensuring efficient airflow while maintaining structural integrity. To ensure their fire resistance and performance, the British Standard BS 476 fire test is commonly used to assess the behavior of flexible duct connectors under fire conditions. In this blog post, we will delve into the significance of the BS 476 fire test and its role in maintaining fire safety in buildings.

What is the BS 476 Fire Test?

BS 476 is a widely recognised British Standard for fire testing and fire resistance of construction products. When it comes to flexible duct connectors, it specifically evaluates the material's ability to withstand fire exposure without losing its structural integrity or contributing to the fire's spread. The test determines critical factors such as flame spread, temperature rise, and smoke production during exposure to flames.

Testing Procedure:

The BS 476 fire test for flexible duct connectors typically involves placing a sample of the connector in a controlled environment. A gas burner is used to expose the sample to flames for a predetermined period. Throughout the test, several parameters are closely monitored, including flame spread, burning droplets or particles, and the time taken for the connector to fail under the fire exposure.

Key Parameters Evaluated:

1. Flame Spread: This parameter measures how far the flame travels along the surface of the flexible duct connector during the test. It helps assess the potential risk of fire spreading to other areas of the building through the ventilation system.

2. Temperature Rise: The BS 476 fire test also records the temperature rise on the surface of the flexible duct connector. This data helps determine if the connector can withstand the heat generated during a fire without getting damaged or contributing to the fire's intensity.

3. Smoke Production: Smoke can be just as dangerous as the flames during a fire. The test evaluates the amount of smoke emitted by the flexible duct connector, as excessive smoke can hinder evacuation and lead to fatalities.

Importance of the BS 476 Fire Test:

The BS 476 fire test is essential in ensuring the safety and integrity of flexible duct connectors used in ventilation systems. Buildings must comply with stringent fire safety regulations, and using BS 476-tested duct connectors helps architects, engineers, and contractors adhere to these standards.

By utilising fire-resistant duct connectors, the risk of fire spread through the ventilation system is minimized, allowing occupants more time to evacuate in the event of a fire. Furthermore, the BS 476 fire test aids in identifying potential weaknesses in the materials used, leading to continuous improvement in fire safety technologies.


In conclusion, the BS 476 fire test serves as a vital tool in assessing the fire resistance of flexible duct connectors. With its ability to evaluate flame spread, temperature rise, and smoke production, the test ensures that ventilation systems remain robust and fire-safe in buildings. Compliance with these fire safety standards is crucial to protect lives and property, making the use of BS 476-tested flexible duct connectors a prudent choice for any construction project. As the industry continues to prioritise safety, adherence to these standards will undoubtedly foster a safer and more secure built environment for all.


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