Technical Articles

What is BS EN 4551:2017

BS EN 4551:2017 is a technical standard that specifies the requirements for evaluating the comfort performance of clothing. It provides guidelines and test methods to assess the thermal resistance, water vapor permeability, and air permeability of textile materials used in garments.

Thermal Resistance Testing

Thermal resistance is an important factor in determining the insulation properties of a fabric. BS EN 4551:2017 outlines the test methods for measuring the thermal resistance of textiles, which involve placing a fabric sample between two temperature-controlled plates. By measuring the heat flow through the sample, the thermal resistance can be calculated.

The thermal resistance value indicates how resistant a fabric is to heat transfer. Fabrics with higher thermal resistance provide better insulation and are more suitable for cold weather conditions. This testing method helps manufacturers understand the thermal performance of their textiles and enables them to design garments that provide optimal comfort in different environments.

Water Vapor Permeability Testing

In addition to thermal resistance, BS EN 4551:2017 also addresses the water vapor permeability of fabrics. This property determines how well a fabric allows moisture vapor from the body to pass through it, reducing the buildup of sweat and enhancing overall comfort.

The water vapor permeability test involves exposing a fabric sample to controlled humidity conditions and measuring the amount of water vapor that passes through it over a specific period. Fabrics with high water vapor permeability are beneficial for activities that involve intense physical exertion, such as sports or outdoor activities, as they allow heat and moisture to escape, keeping the wearer dry and comfortable.

Air Permeability Testing

Air permeability is another important factor in assessing the comfort performance of clothing. BS EN 4551:2017 provides test methods to measure the airflow resistance and air permeability of fabrics. These tests determine how easily air can pass through a fabric, affecting its breathability.

Fabrics with high air permeability allow for better ventilation, helping to regulate body temperature and prevent overheating. This is particularly important in active wear and outdoor apparel, where comfort during physical activity is crucial. By using the standards outlined in BS EN 4551:2017, manufacturers can ensure that their garments offer optimal air permeability, reducing discomfort caused by heat buildup.


BS EN 4551:2017 provides essential guidelines and test methods for evaluating the comfort performance of clothing. By measuring factors such as thermal resistance, water vapor permeability, and air permeability, manufacturers can design garments that offer optimum comfort in various conditions.

Understanding and adhering to these technical standards allow for the production of high-quality textiles that provide insulation, allow moisture transfer, and promote good airflow. Whether it's for everyday clothing or specialized sportswear, compliance with BS EN 4551:2017 helps ensure that garments are comfortable, functional, and meet the expectations of consumers.



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