Fire ratings and classifications can be complex and, if you are unsure of what you are looking for, it can make it difficult to find the right door for your project.
At Selo, we believe in simplifying complex building methods. Whether that be through our product innovation, or through educating the market on industry best practices.
One of the biggest questions we get asked around classification is ‘what is the difference between FD and EI fire rated doors? And which is better?’
With over 16 years’ experience in innovating solutions for fire rated doors, we have answered the question below.
What is an FD fire rated door?
FD fire ratings are classifications of performance on how long a door can resist a fire. The required ratings are commonly FD30, FD60 or FD120 to indicate how many minutes a doors structure on integrity will resist the passage of fire.
For example:
FD30: The door has been shown to resist the passage of fire for at least 30 minutes.
FD60: The door has been shown to resist the passage of fire for at least 60 minutes.
FD120: The door has been shown to resist the passage of fire for at least 120 minutes.
In the UK, building regulations require fire doors to be tested and certified to either BS 476-22 or EN 1634-1. However, the doors tested to BS 476-22 don’t include smoke so further testing is required.
In the latest revision of building regulations, all national standards have been removed so all of the parts of BS476 for both reaction and resistance to fire and only the EN’s can be used from the end of the 5-year coexistence period which is 2nd September 2029.
What is an EI fire rated door?
The EI rating defines ‘(E) Integrity and (I) Insulation’, also indicates how many minutes a doorset/assembly will resist the passage of fire structures for integrity and insulation in minutes. The same format applies:
EI30: The door has been shown to control the spread of fire and heat for at least 30 minutes.
EI60: The door has been shown to control the spread of fire and heat for at least 60 minutes.
EI120: The door has been shown to control the spread of fire and heat for at least 120 minutes.
What is an E fire rated door?
The E rating defines (E) Integrity also indicates how many minutes a doorset/assembly will resist the passage of fire structures for integrity in minutes. The same format applies:
E30: The door has been shown to control the spread of fire for at least 30 minutes.
E60: The door has been shown to control the spread of fire for at least 60 minutes.
E120: The door has been shown to control the spread of fire for at least 120 minutes.
E/EI fire rated doors are classified in accordance with BS EN 13501-2, a European standard, and where required the insulation is included to prevent temperature rising on the unexposed side of the door. However, the doors tested to EN 1634-1 don’t include smoke so further testing is required.
What is fire rating ‘integrity’.
Integrity is used to test the structure of the door during the fire test and if the door would prevent the fire passing through. Integrity is measured by placing the door in a furnace then heated to over 800°C and for longer durations over 1000°C to a standard Iso time temperature curve. The integrity of the door is then tested by:
- Fissures or openings which would allow flames passing through or charring spread to the unexposed face. A cotton pad, that is placed on the other side of the door to the fire to check for this mode of failure. If the cotton pad ignites within 30 seconds, the door fails.
- Sustained flaming occurs on the unexposed side for 10 seconds or more, the door fails.
- Should a gap gauge of 6mm passing through the furnace and being able to traverse 150mm, the door fails.
- If a 25mm gap gauge passes through the specimen, then the door fails.
If any of these criteria occur, then the door will fail the EI performance criteria (the cotton pad test is not relevant to integrity only doors). A timer is started from the beginning of the test to measure the duration of integrity of the door.
A failure of integrity automatically fails insulation.
How is insulation measured?
During the same furnace and fire test as integrity, insulation is measured by the door’s capacity to resist heat transfer from the exposed face to unexposed face. The insulation failure criteria in relation to fire resistance testing to EN1634-1 and classification to EN13501-2 is for doors with an average measured increase in temperature across the thermocouples on the door of 140 K over ambient temperature or 180 K over ambient of any individual thermocouple.
How is smoke resistance defined?
For BS 476-22 doorsets and assemblies they must be tested to BS 476-31 for their resistance to the passage of smoke at ambient temperature. Then S can be added to the classification, for example FD30S.
For EN 1643-1 doorsets and assemblies they must be tested to EN 1634-3 for their resistance to the passage of smoke at ambient temperature. Then Sa can be added to the classification, for example EI30Sa or E30Sa.
For EN 1643-1 doorsets and assemblies the maximum leakage rate measured at ambient temperature, and at a pressure of up to 25 Pa only, does not exceed 3 m3 ³/h per metre length of gap between the fixed and moveable components of the doorset (e.g. between the door leaf and the door frame) and shall be completed with information as to whether or not the leakage from the bottom of the door leaf (leaves) has been included in the test.
The Sa classification shall be completed by “3” and “4” to indicate whether the doorset has been tested with seals on 3 sides (vertical sides of the door leaf/leaves and head) or on 4 sides (i.e. additionally including threshold).
What is the future of the FD fire rated standards and BS476?
In the latest revision of building regulations, all national standards will be removed in a stepped process, so all of the parts of BS476 for both reaction and resistance to fire and only the EN’s can be used from the 2nd September 2029.
In addition, all opinion-based Field of Application reports and engineered assessments have also been taken away as a way of demonstrating fire resistance performance. All reports used for fire doors will have to have a formal classification to EN13501-2 and this means all that can be covered is what has been directly tested and is further covered by Direct Field of Application rules and or extended application rules from the EN15269 series of EXAP standards.
Selo recommendation
When deciding what type of fire rating you need to provide, it’s important to consider the fire safety of the entire building as a system and how the people inside will be protected. Fires in buildings pose a huge threat and can cause several problems. Fire doors should not be considered in isolation but as part of a compartment system.
Given the latest building regulations and second phase of the Grenfell enquiry, we recommend that, to future proof your project, developers and contractors procure fire doors that are at least E fire rated under the European system.
Toxic smoke inhalation is responsible for more deaths than the fires themselves, which is why many buildings now have smoke control dampers, as well as riser doors as the fire protection strategy. Smoke protection must be considered when planning the fire safety of a building.
If you have any questions on what type of fire rated door you need, please speak to one of our specialists who will be able to help you.
Reference: FIS – Walls as a System.