Fire Protection Blog

What is the difference between Reaction to Fire and Fire Resistance?

We explore this issue looking at one of our unique products Aithon PV33 that can provide reaction to fire or structural fire protection to timber beam, columns and walls providing a superior finish to its rivals. However, we must understand more about our timber, what is the requirement and is the product fully tested.  

Reaction to Fire

Reaction to Fire tests are used to evaluate the contribution of a material and building elements to fire growth. How will the timber/wood react in the case of fire? Understanding your requirement is important and guidance should be sought from Approved Document B of the Building Regulations.

European Classifications:
A1 / A2 - Non-combustible materials
B – Combustible materials with very limited contribution to fire
C - Combustible materials with limited contribution to fire
D - Combustible materials with medium contribution to fire
E - Combustible materials with high contribution to fire
F - Combustible materials which are easily flammable

European testing also looks into smoke emission level and flaming droplets which can have major impacts on fire spread.
s1, s2, s3 [m2/sec2] deals with smoke intensity
s1 - Speed of emissions absent or weak
s2 - Speed of emissions of average intensity
s3 - Speed of emissions of high intensity
d0, d1, d2 = description of burning droplets
d0 - No dripping 
d1 - Slow dripping
d2 – high dripping  

What product can I consider for reaction to fire on timber?

The Aithon PV33 system has been tested on timber and wood derivatives with a minimum thickness of 10mm and a density equal to or greater than 390kg/m³, compared with other systems and flame retardants which may have to be at least 20mm thick or greater to achieve an equal performance of Euro B (Class 0). Aithon PV33 achieves a Euro-Class B s1 d0 reaction to fire and provides an exception natural finish. To provide EN13501-1 Class B reaction to fire (equivalent to UK Class 0, BS467:Part6 & BS476:Part7). Reaction to Fire Euro Class B is said to be a more robust and common test nowadays than a Class 0 as it measures heat release, fire growth rate, smoke levels and flaming droplets.

Fire Resistance

We quite often find that periods of fire resistance get confused with the above reaction to fire testing. However, the testing is very different to achieve.

Resistance to Fire deals with protecting a loadbearing structure to resist fire for a determined amount of time eg 30, 60, 90 minutes plus. This could be a floor, wall, door, beam or fire barrier construction. For example, the European rating could be REI 60 which means that the whole system would provide stability, integrity and insulation for 60 minutes without failure in that time period.   
R - Load bearing capacity is to maintain loadbearing without the loss of structural stability
E - Integrity to withstand fire exposure without fire passage through to the other side in the form of flames and smoke.
I - Insulation to withstand fire exposure on one side only, without the transmission of fire in the form of significant heat transfer.

What product can I use for periods of fire resistance?

The Aithon PV33 system is tested to EN13381-7 a test method for determining the contribution to the fire resistance of structural members. Aithon is one of the few products to go through this rigorous testing and is used on major projects by architects throughout the World. Like steel members the timber is now calculated technically through our calculation system to provide accurate data taking into account various criteria including integrity and stability. It is not as simple as defining the number of coats to achieve a performance, it is a technical calculation, knowing about the building, the load on the timber and the substrate itself.  When deciding on a product it is important to establish that the product has been fully tested. It should be tested to the correct standard and not just indicative testing and the test solution should be backed up. On site the correct loading rate should be measured to ensure the correct quantity of material is applied to achieve the desired fire protection requirement. Aithon PV33 is one of the few products on the market for timber to benefit from the stringent European Technical Assessment (ETA) process. 

For further information, click on the link: Aithon PV33