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Understanding fire certificates: The essential guide

It often comes to our attention that most companies are very reticent to share and explain fire certificates with their customers. However at Redwood, we are always completely honest about what our fire certificates show, so you can choose an appropriate wood coating for your project. 

To continue with our open and honest approach, this blog will provide the ultimate guide to understanding fire certificates, to ensure your safety and full compliance with fire safety regulations. 

Key factors to consider 

There are a number of factors to consider when selecting an appropriate wood coating for your project, particularly looking at what certification is required for the project you’re working on. 

Firstly, you must understand whether you want to uprate or maintain the timber substrate. 

What is the difference between uprating and maintaining? 

Uprating the timber substrate will take it to the required level of fire retardancy. To achieve this you will need a lacquer that will increase the integrity of the substrate.  

Maintaining the substrate will keep it at the existing level of retardancy. For this to be possible, you will need to choose a coating that has the same certification.  

Check out our YouTube video for more information. 

The product type tested 

Before using a new product, it is vital to know the finer details of the fire certificate, such as the type of product tested, as it can have an effect on user safety and compliance with fire safety regulations. 

Important factors to review are the substrate used and its density, the type of surface, whether it is veneer or coated, or whether it is a smooth surface without joints. As well as the product’s application rate and thickness. 

A fire certificate, issued by the fire testing body, will detail this, and highlight any limitations and warnings if the product is subsequently used in different conditions to those carried out in the test, which could affect performance and safety. 

Different fire certificates available 

A fire certificate will rate products on their fire behaviour and focus on additional classifications such as smoke production, burning droplets or particles and their performance in reaction to fire. 

The following fire certificates are available, and both maintaining and up-rating results can be achieved: 

UK – BS 476 Parts 6 and 7 

BS 476 Part 7 (Class 1)  

Measures the spread of flame over a given substrate during a 10 minute period. During this period the flame spread is checked at 1.5 minute and 10 minute intervals. If during either check the flame has not extended past the 165mm limit it will be certified as a Class 1 surface. If the flame extends past the limit it will be classified as either Class 2, 3 or 4, depending on severity of spread. 

BS 476 Part 6 – Fire propagation test 

This certificate measures the contribution of a material to the growth of a fire. The sample is tested in a fire propagation chamber, whereby fourteen jets of a gas pipe burner at a distance of 3mm are applied over a 20 minute period.  

The test measures the temperature difference between the ambient temperature and the temperature in the chimney of the test chamber at specific intervals compared to a non-combustible sample undergoing the same process. The intervals are as follows: 30 second intervals up to 3 minutes, at 1 minute intervals up to 10 minutes and at 2-minute intervals up to 20 minutes. These temperature measurements are used to calculate sub-index scores (i₁, i₂, i₃) for each stage of the test. 

The sub-index scores are then combined to determine the overall fire propagation index (I). To pass the test, the sub-index scores must not exceed 6, and the overall fire propagation index must not exceed 12. The test helps assess the material’s potential contribution to the spread of fire. 

If the submitted samples successfully pass both parts 7 and 6 of BS 476, a Class 0 rating is achieved.  

EU – EN BS 13501-1-2007 

This standard is relatively new and will replace the BS 476 certification within 2 years. It was created to merge the current European fire certifications into one universal rating system. 

The BS EN 13501 rating categorises material into different Euroclasses determined by the combination of two separate tests: the ISO 11925 Ignitibility Test and the BS EN 13823 Single Burning Item Test. 

The defined Euroclasses are A1, A2, B, C, D, E, and F: 

  • Euroclass A1: Non-combustible materials with the highest level of fire resistance 
  • Euroclass A2: Materials with limited combustibility 
  • Euroclass B: Materials with low or moderate combustibility 
  • Euroclass C: Materials with normal combustibility 
  • Euroclass D: Materials with higher combustibility 
  • Euroclass E: Materials with significant combustibility 
  • Euroclass F: Materials with the highest level of combustibility 

ISO 11925 Ignitibility Test  

This test assesses the ease with which a material can be ignited and the potential for secondary ignition through burning droplets or debris. 

During the test, the material specimen is positioned vertically, with two filter papers placed below it. A small flame is then applied to either the face or edge of the sample for a duration of 30 seconds, followed by a 30 second period without a flame. The result of the test is determined by whether the flame reaches a point 150mm above the initial flame point and whether the filter paper beneath the sample is ignited by burning droplets or debris. 

Unlike some other tests, ISO 11925 does not provide a specific score or index on its own. Instead, its results are combined with the subsequent BS EN 13823 test to generate an overall fire rating for the material. This combined assessment helps evaluate the material’s fire performance comprehensively, taking into account both its ignitibility and other factors such as heat release, flame spread, and smoke production. 

BS EN 13823 Single Burning Item Test 

This test determines heat release, surface spread of flame and smoke production/density when exposed to a single burning item (SBI). This is achieved by attaching the test specimen to a trolley beneath an exhaust system. The base of the specimen is then subjected to a single burning item, a sandbox burner fuelled with propane, for a duration of 21 minutes. 

During this timeframe, data is collected to measure heat release (via the exhaust system) and smoke production/density (via light beam for density and exhaust for production). The fire growth rate index is then calculated using total heat release over the first 10 minutes of the test, the smoke growth rate and total smoke production over the first 10 minutes of the test. 

In addition to this, visual observations are made for lateral flame spread (by reaching the end of the long wall of the sample at a height of 500mm and 1000mm), and for flaming droplets/debris. 

The combined results from the above tests are displayed in the form of 3 elements: the overall class, the smoke production and presence of burning droplets. The class is indicated by the previously mentioned lettering system (B to D for wood), the smoke is indicated by s1, s2, or s3 (best to worst) and the presence of burning droplets is indicated by d0, d1 and d2. For example, the highest classification to the lowest would be: B-s1, d0 to D-s3, d2. 

EU and UK fire rating systems  

It is vital to understand the differences between the UK and EU fire rating systems. At present the British BS 476 certification is available alongside its European equivalent, BS EN 13501-1-2007, but this is a temporary measure and will be phased out within 2 years. 

When comparing UK and EU systems there is often confusion as to how the ratings compare. To simply things, we’ve included this table comparing BS and EN Classifications: 

  British Classification   European Classification 
Highest rating  Non-Combustible   A1 
  Limited-Combustibility  A2 
  Class 0    


B-s1, d0 to B-s3, d2 

  Class 1    


C-s1, d0 to C-s3, d2 

  Class 2   
  Class 3    


D-s1, d0 to D-s3, d2 

Lowest rating  Class 4   F 


Meeting the highest standards 

At Redwood we are experts on fire rated lacquers. We are thrilled to offer Hesse Lignal’s FANTASTIC range meets the highest rating B-s1, d0 for the fire classification to the EN13501-1. 

For the highest rating lacquers that meet your needs, contact us on 023 9223 3310 or email