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Demystifying Fire Damper Classifications

Approved Document B defines Fire Resistance as the ability of a component or a building to satisfy, for a stated period of time, some or all of the appropriate criteria given in the relevant standard. The resistance is a measure of certain criteria such as resistance to fire penetration, and is measured in minutes. The Fire Resistance is defined in the classification report which is issued by a third party (notified or approval body), and is based on testing that has been conducted against the relevant test standards. There are specific standards that cover classifications for different types of products. 

Classifications for Fire Dampers are covered in the standard BS EN 13501-3:2005+A1 2009. Before looking at these classifications in detail, it is important to consider what a Fire Damper is. There can be various names that they are known by within the building services industry.

A Fire Damper is a damper that:  

  • Is designed to maintain compartment integrity when closed
  • Designed to close and stay closed
  • Has its own thermal release mechanism

Within Approved Document B, it references both Fire Dampers having an ‘E’ classification, and Fire and Smoke Dampers having a ‘ES’ classification.

It should be noted that Fire Dampers are not Smoke Control Dampers, and we will be covering these in a separate blog dedicated to Smoke Control Dampers.

The terms motorised fire dampers, fusible link fire dampers, motorised fire smoke dampers, and MFSD’s are all used within our industry. Ultimately, if a damper is expected to behave as described above and maintain compartment integrity, then it is a Fire Damper.   

A damper that is designed to allow the movement of Smoke away from a fire is a Smoke Control Damper, which has a different classification standard.

Shown below is an example of a Fire Damper classification: 

EI120(ve ho i↔o )S, 10,000  (300Pa) 

E = Fire resistance integrity of the damper. This is mandatory, and is expressed as a function of time in minutes.  It is determined by conducting a Fire Resistance test to BS EN 1366-2:2015.  Failure criteria includes the damper leakage going over 360m3/hr/m2, sustained flaming, or holes appearing that are big enough for a gap gauge to penetrate through. 

I= Insulation rating of the damper. Whilst not a mandatory requirement (in the UK), depending on the space risk determined during design, a damper with an insulation classification may be required if the fire strategy demands it.  As above, this is determined by conducting a Fire Resistance test to BS EN 1366-2:2015 and is expressed as a function of time in minutes.  Failure criteria are when one of the thermocouples exceeds 180oC above ambient, or the average temperature increase of all the thermocouples exceeds 140oC above ambient.

S= Low Smoke Leakage rating of the damper. This is not a mandatory requirement to achieve a damper classification, but checks should always be done to determine if it is required for the application.  As above, this is determined by conducting a Fire Resistance test to BS EN 1366-2:2015, and is expressed as a function of time in minutes.  In addition to the Fire Resistance test, you also need to conduct a damper blade leakage test on the smallest damper at ambient temperature to BS EN 1751:2014.  Failure criteria is when the damper closed blade leakage exceeds 200m3/hr/m2. 

120 = This is the time (in minutes) of the classification, and is applicable to all of the criteria shown in the classification. There are set time categories as defined in the standard BS EN 13501-3:2005+A1 2009 

ve = This shows that the damper can be installed vertically, i.e. in a wall.   

ho = This shows that the damper can be installed horizontally, i.e. in a floor/ceiling.   

io = I defines inside, and the o defines outside. This shows that the damper has been tested with fire attack in both directions.  The classification standard still allows you to classify fire attack in one direction. In that scenario, you would only have an arrow in one direction. 

10,000 = This shows the number of cycles that the damper has been tested to as defines in BS EN 15650:2010.  A cycle is defined as going from open to closed and back to open, or closed to open and back to closed. 

300Pa = This shows the damper differential pressure used in the Fire Resistance Test. The standard test pressure is 300Pa, so as such it is not always declared as part of the classification on a DoP. There are however, some markets in Europe that specify 500Pa as a test pressure, and this will be declared as part of the classification. 

As the E part of the classification is mandatory, if you fail on any one of the E criteria, then you automatically fail all of the classification criteria including the optional ones. 

It is important to remember that the classification is only applicable to the installation method that was tested.  If the installation method changes, then it can’t be assumed that the classification will be the same.  Many manufactures have a vast range of installation methods, and as such there could be a range of classifications, due to the type of wall construction or penetration seal used in in the test.   

Historically in the UK market, an ‘E’ classified damper, such as a curtain bladed fire damper would be considered a fusible link damper, as they traditionally would be fitted with a fusible link, and a ‘ES’ classified damper would always be considered an automatic damper. The problem with this approach is that the damper classification, and the method of activation are not linked; they are two separate issues.   

It is possible in today’s market to get a damper with a ‘EIS’ classification, but with a fusible link.  This may not seem like a big issue, but you need to be careful when reviewing the requirement of Approved Document B or BS9999:2017.

For example in ADB section 10.16 states: 

10.16 An ES classified fire and smoke damper which is activated by a suitable fire detection system (method 4) may also be used for protected escape routes

The methods are defined in section 10.12 of ADB 

  • Method 1 – thermally activated fire dampers;
  • Method 2 – fire resisting enclosures;
  • Method 3 – protection using fire resisting ductwork;
  • Method 4 – automatically activated fire and smoke dampers triggered by smoke detectors.

There is a similar statement in BS9999:2017: Protected escape routes 

  • Method 1 should not be used where ductwork passes through or serves an escape route, as large volumes of smoke can pass through without activation of the thermal devices and E-rated fire dampers have no performance rating in terms of smoke resistance. 
  • Methods 2 and 3 should be used only where ductwork does not serve the escape route it passes through. 
  • Method 4 may be used for extract ductwork passing through the enclosures of protected escape routes, both where the ductwork does and does not serve the escape route. 

As before. the 4 methods are defined, in this case in section General 

Where air handling ducts pass through fire-separating elements, such as compartment walls or the enclosures to protected escape routes, then the integrity of those elements should be maintained, using one or a combination of the following four methods: 

  • Method 1: thermally actuated fire dampers; 
  • Method 2: fire-resisting enclosures; 
  • Method 3: protection using fire-resisting ductwork; 
  • Method 4: automatically actuated fire and smoke dampers triggered by smoke detectors. 

Whilst an ‘EIS’ classified damper with a fusible link exceeds the requirements of being a ES classified, its release mechanism does not lend itself to being activated by a suitable fire detection system. It therefore should not be used for protecting an escape route. This situation could be resolved by either changing the method of activation to one that can be activated by a suitable fire detection system (if the design of the damper allows this), or by selecting a different damper. 

To sum up...

  • Dampers should always be selected based on the classification of a specific installation method.   
  • The specification and classification of the supporting construction needs to reflect the damper installation method chosen. Whilst a damper may have a classification of E120S, consideration must be given to the standard supporting construction that was used in the test. If the damper was tested in a wall that has a classification of E120 then it cannot be use in a wall of lesser classification (for example E60), without additional data.
  • Damper classifications are available from the damper manufactures in their Declaration of Performance (DoP). 
  • If you are presented with a classification that makes a statement such as ‘2 hour fire rated’ then the there is a chance that the damper is may not be classified under BS EN 13501-3.  Check with the manufacture/supplier to get further clarification. 
  • Do not confuse method of activation with damper classification as they are two different issues. It is no longer applicable to expect that all fusible links dampers have an ‘E’ classification and all dampers with an electrical actuator are ‘ES’ classified as a minimum.  

Additional information can be found at: