“Sampling” in fire testing of construction products

Introduction

Sampling is a key step in the process of assessing and verifying the constancy of performance of construction products undergoing testing. It provides detailed information about the tested structure, its material composition, and key design features, which allows for the proper interpretation of test results in relation to the product intended for market introduction. The primary goal of sampling is to confirm that the tested product is identical to the product that will be marketed, while also ensuring that the sample taken faithfully represents the final product.

In the case of products with fire properties, proper sampling is particularly important as it has a direct impact on the level of fire safety.

Legal requirements and market practice

In accordance with Regulation (EU) No 305/2011 of the European Parliament and of the Council , laying down harmonised conditions for the marketing of construction products (concerning CE marking), and the Regulation of the Minister of Infrastructure and Construction of 17 November 2016 on the method of declaring the performance of construction products and the method of marking these products with the construction mark, the obligation to perform sampling in the AVCP 1 and 1+ systems is clearly defined.

Despite this, for many years this process was often overlooked, primarily due to established market practices and limited awareness of the importance of sampling in assessing the performance of construction products. An additional barrier was posed by complex procedures that required advanced technical skills and were time-consuming. As a result, sampling was not given the attention it deserved, despite its crucial role in ensuring the reliability of test results and product compliance with legal requirements.

Increased awareness and new requirements

In recent years, many notified bodies have begun to place greater emphasis on proper sampling, introducing stringent requirements for this process. According to the guidance contained in document NB-CPR/15/639r3 , issued by the Coordination Group of Notified Bodies (GNB-CPR), regarding sampling in AVCP 1 and 1+ systems, sampling is a key element in assessing and verifying the constancy of performance of construction products. Failure to properly conduct sampling increasingly often results in refusals to perform laboratory tests and issue test reports.

It is worth noting that the sampling provisions apply not only to products covered by the CE marking, but also to construction products marked with a national construction mark. 

Sampling methods

The choice of sampling method depends on the product type and production stage. The most commonly used include:

· Sampling directly from production – allows you to monitor the process in real time and provides certainty as to the origin of the samples.

· Sampling from the manufacturer’s warehouse – random selection from finished products, especially useful after production.

Sampling of custom products (“made to order”) – in the case of custom production, samples are prepared specifically for testing, usually in the most difficult variant (“worst case”).

· Prototype sampling – used when the product is in the development stage.

Each of these methods should be carefully documented, indicating the sampling location, labeling method and information about the origin of the samples.

Challenges of Sampling for Fire Tests

Due to their complex design, large size, and high manufacturing costs, fire-resistant products present a particular challenge when it comes to sampling. A prototype is typically used, as the manufacturer typically prepares only one unit for fire testing. If test results prove negative, design modifications are implemented and testing repeated to achieve the required level of safety. In such cases, sampling must always be conducted with the utmost care to ensure the sample faithfully reflects the design of the target product. This is especially important in fire testing, where the sample is completely destroyed, making subsequent analysis impossible.

Documentation and reporting

Each sampling step requires thorough documentation. The report should include design details, manufacturer information, the number of samples taken, the date and location of sampling, and labeling. This transparency guarantees the credibility of the entire process. The sampling report is then referenced in the fire test report, facilitating the replication of the tested solutions and confirming their consistency with the product being marketed.

Summary

In recent years, there has been a significant shift in the approach to sampling in the conformity assessment process for construction products. Awareness of the importance of this step has grown, and notified bodies across Europe have begun to place greater emphasis on proper sampling, viewing it as an essential element in assessing and verifying the constancy of performance of products.

Proper sampling is not only a formal obligation arising from legal regulations, but above all, a crucial element in ensuring the safety of end users. It is precisely through carefully conducted sampling that it is possible to obtain reliable test results that reflect the actual properties of the product being introduced to the market.