The European classification standard for fire retardant products, EN 16755, was approved by vote in June 2017 and is called “Durability of reaction to fire performance - Classes of fire-retardant treated wood products in interior and exterior end use applications”. The new standard replaces the previous technical specification CEN / TS 15912 with the same name, but since the two do not differ in their requirements, the products that have been tested and approved according to the CEN / TS 15912 will continue to be approved. The aim of the durability test is to assess the hygroscopic properties of the fireproofing agent and its long-term reaction to fire properties after weather exposure, not the properties of the wood itself.
The basic principle of accelerated aging is that a material is exposed to recurring cycles in a climate chamber that is meant to simulate a natural exposure to rainfall, heat, drying, UV rays, etc.. Before the testing process is initiated, samples are taken from the actual batch, which are weighed and fire tested in accordance with the ISO 5660-1 (concalorimeter) in order to determine the reaction to fire parameters. The results give indications of the durability of reaction to fire properties that can be expected under specific conditions such as normal indoor climate, increased humidity in interior installations and installation in an exterior environment.
The technical specification consists of four classes. Inbound data is compared with outbound data after testing has been performed. In order to achieve an approved result, the deviation for each value may be a maximum of 20%. Please note that this limit for permissible deviation must not be exceeded even if the classification according to the EN13501-1 is retained after the test has been completed. An example: if the input parameter is THR 5.0 and the output parameter is THR 6.5, then the deterioration is 30 % and thus cannot be approved.
The basic principle of the hygroscopics test is that it prescribes the procedure of determining the equilibrium moisture content after exposure to normal conditions with high relative humidity of (90 ± 5)% at (27 ± 2) ° C, depending on the DRF class. The method is based on the NT Build 504 , with changes in A.3 with a further humid climate condition included for testing. It is a modified and extended version of the ASTM D3201-94 (with the same title) .
The extension aims at generating more replicable and reproducible results by requiring a ratio of equilibrium in the moisture content. The standard EN 16755 includes some additional modifications, mainly testing for two internal conditions: dry and humid.
To test reaction to fire properties after weather exposure, method A or B should be used as mentioned below.
For testing of hygroscopic properties, the following test method should be used:
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