Frequently Asked Questions
- Fire Retardants
- FR Products
- Harmonised Euroclasses system (for reaction-to-fire)
- How to interpret fire test results
- More questions on FR wood subjects
- Wood under fire conditions
Fire Retardants
Are fire retardants permanent?
In principle, the fire retardant treatment can be assumed to be permanent if the treatment type has been chosen according to the end use conditions (indoor, outdoor, weather, etc.). Maintenance is required for outdoor applications. Please follow the recommendations from the manufacturer.
Special care should always be taken with water contact and humid conditions.
Are FRs harmful to people or to the environment?
Safety in use of fire retardants is obtained by following manufacturers recommendations (handling and safety instructions) as for any chemicals. Note that direct contact with the pure chemicals may cause some effects like skin or eye irritation. Pressure pre-treatment types are factory applied and intumescent coatings are usually site applied by professionals, thus minimising any risk.Use of FR wood products as part of a whole system (like building) will result to decreased number of fires and decreased emissions during fires. This will also result to improved safety of people compared to untreated wood.
Are there differences in FR solutions for internal and external usage?
Yes, there are different types: Inorganic salt type formulations are for dry interior use with low humidity, humidity resistant types for all interior situations and protected external situations, and leach resistant polymer types are for fully exposed exterior situations.
New classes for the durability of fire performance of wood products in interior and exterior applications are available and European standardisation underway. These classes will increase the reliability and confidence of FR wood products and assist manufacurers to document the durability of their FR products and users to formulate relevant requirements.
FR Products
Can an untreated decorative veneer be placed on FR-treated wood or wood product?
Not without reducing the fire performance, particularly the fire spread characteristics. It is essential to treat the veneer as well as the substrate. However, some regulations may allow addition of very thin decorative veneers without reducing the fire performance class.
Can FRs be applied to pre-treated or pre-coated wood?
Each case needs to be considered on its own merits to assess that incompatibility of treatments, or incorrect choice of FR treatment does not negate the fire properties of the treatment.
Can there be service-life problems?
This depends very much on the timber substrate, the treatment used and the environment in which it is used. For example, a brush on intumescent coating at low level in a Sports Hall would need regular checking and maintenance, whereas a humidity resistant pressure treatment may be maintenance free for the life of the timber in the same environment.
Harmonised Euroclasses system (for reaction-to-fire)
What are the consequences of the Euro classes system?
The reaction to fire test methods are now harmonised in
When does the new system start working?
The Euroclass system with test methods and classifications was decided by the EU Commission in 2002 . Each country has then to adapt the new methods into their national regulations. However, the national implementations occur with different speed. Some countries started the implementation already in 2002, while others have not yet decided in 2006.
Will a test made in one country be acceptable in another country?
Yes.How to interpret fire test results
Does no ignition by e.g. cigarette lighter indicate that the product is acceptable for any use?
A small fire application can only show if there is any effect at the lowest level of fire performance. However, to assess performance of FR treatment in a real fire case the experimental setup must reflect real fire conditions. Thus, ’no ignition’ in a cigarette lighter test does not alone ensure that the product would be in the class of high fire safety performance.
Testing according to the harmonised standards or otherwise recognised standard tests is strongly recommended to get a realisctic information on possible improved fire classification.
Improvement of structural wood elements, the role of FRs?
Fire retardants are formulated to improve the reaction to fire properties of a material, i.e. ignition, fire spread and rate of heat release. Generally there is no improvement in fire resistance time values. However, intumescent coatings may be used to protect timber structures to get improved fire resistance in the same way as steel structures are protected, although such improvement is limited because of the type of intumescent char.
Reaction-to-fire/fire resistance; what's the difference?
Reaction to fire describes the early phases of fire; ignition, heat release, fire spread, smoke production, and relates to products and materials. Fire resistance deals with the load bearing capacity, integrity and insulation properties of structural elements, such as wall and floor elements, under fully developed fire conditions.
More questions on FR wood subjects
Calculation of fire resistance of timber construction?
Detailed calculations rules are given in Eurocode 5, Design of Timber Structures, Part 1-2, General Rules - Structural Fire Design, EN 1995-1-2.
What is FR wood?
Timber or a wood based substrate that has received a treatment either during its manufacture, prior to its installation, or in situ, that will improve its reaction to fire performance in relation to a recognised test method.
When do I need to fire protect wood?
As soon as there is a requirement, statutory or otherwise, at a higher level of security for performance under fire than that met by untreated wood.Wood under fire conditions
At which temperature does wood start to burn?
Pyrolysis of wood under fire conditions starts around 270 oC and ignition under pilote fire conditions usually occur around 330 – 360 oC.
Do FRs change the charring rate?
FR pre-treatments do not generally change the charring rate. Intumescent coatings will delay the start of charring.
What is the charring rate of wood products?
National standards and Eurocode 5 (EN 1995-1-2:2004 General Rules - Structural Fire Design) define the charring rate, which depends on species, density and dimensions of the structure.
The basic charring rates according to Eurocode 5 are:
- Hardwood (density at least 450 kg/m3): 0,5 mm/min
- Softwood, beech and LVL: 0,65 mm/min
- Panels: 0,9 - 1,0 mm/min
What is the Euro class of solid wood and wood- based panels?
Generally, class D is achieved, if the panel density is at least 400 kg/m2, but there are also limits in terms of panel thickness, joints and type of end use application.
Detailed reaction to fire classes for wood based panels have been determined by classification without further testing (CWFT) according to a Commission decision and is included in the harmonised product specification en 13986.