Below are some of the most frequently asked questions asked by HVAC fire duct workers about commercial kitchen smoke and fire ducting.

Q. How is a commercial kitchen fire duct rating measured?

Commercial kitchens are a unique ventilation requirement.  The extraction systems for commercial kitchens are subject to the migration of combustible contaminants, namely grease. Because the inside of these ducts may become lined with grease particles, it creates a potential fire risk.  

The EN tests standard EN 1366-1 has a section dealing with combustible linings.  

In section A.6:

“For kitchen extraction ducts or where internal combustible linings are used, additional temperature measuring points have been specified, together with a criteria of 140°C/180°C.”

During an EN 1366-1 Type A test, 4 thermocouples are positioned inside the duct section inside the furnace.  They measure the surface temperature of the metal to the temperature tolerances above.

This gives an accurate reading of the protection that insulation provides a kitchen duct with a fire surrounding the duct.

A classification report to EN 13501-3 will reference this result as “Insulation for combustible internal linings”.

For more information about kitchen extract, contact us or call +353 1 456 8200.

Q: Do I need to insulate inside the kitchen?

The latest guidance by the ASFP found in the Blue Book EN Fire Resisting Ductwork 2nd Edition 2020, Figure 7, shows that 30 minutes Insulation performance is recommended for kitchen extract ducts inside the kitchen for means of escape purposes.

Insulation is applied to kitchen ducts as they pass through other compartments.  A fire in another compartment, unrelated to the kitchen, could potentially ignite the grease and cause a fire to cascade throughout a building.  We use insulation to mitigate this risk.

For more information about kitchen extract, contact us or call +353 1 456 8200.

Q: Can I put a fire damper in a kitchen extract?

Fire dampers should not be used in the extract system of a commercial kitchen. (According to the regulation BS 999:2017 Section

Fire dampers are used to maintain compartmentation in the event of a fire. Compartmentalisation is the foundation of all fire strategy, restricting the spread of fire from one location to another by ensuring the envelope of the compartment is capable of restraining a fire from migrating through a building.

The presence of grease would render fire dampers inoperable, so they offer no protection against fire and damage. Compartmentation of a commercial kitchen is maintained by the existence of a fire resistant duct, one that is manufactured and tested to the European Standard EN 1366-1 and classified to EN 13501-3.
Lindab Thor Duct ® manufactures EN standard approved kitchen ductwork. More information here.

If you are interested in becoming a licensee manufacturer of Lindab Thor Duct ® ductwork in your region, you can find out how to apply here

Q: What is the standard for commercial kitchen extract ductwork?

The second edition 2018, Appendix D, section D6 states “it is essential that the installed system complies with BS EN 1366-1”.  The tests are fire inside (Type B) for integrity (E) and insulation (I) for the same period of time as the compartment through which the duct passes.  Testing for fire outside (Type A) is an additional requirement that the internal surface be insulated in any adjacent compartment. DW144 3rd Edition 2016 states that fire safety products must be properly manufactured, tested and certificated in accordance with the latest BS-EN requirements. (Par M.1)

In the UK and Ireland, guidance for Kitchen Extract systems is given through DW172. This is because UK and Ireland are leading in standards development for fire protection. 

In mainland Europe, it is unclear what the guidance is for kitchen extract.

Located in UK or Ireland?

  • Talk to us about how Lindab Thor Duct ® products can ensure you reach the relevant standard for fire safety compliance. Contact us or call +353 1 456 8200.

Location outside the UK or Ireland?

If you want to have a system that is as safe as is possible, having considered the fire risks,  Lindab Thor Duct ® is the best solution for you. 

Q: Do cleaning doors need to be fire tested?

Cleaning doors are an essential element of a commercial kitchen extract system.   

“Access panels should be of a construction that has at least the same fire resistance as the element they fit into”. (BS 9999:2017 Section 32.4).

The number of access doors is determined by the presence of detailed cleaning specification/method.  In the absence of a cleaning specification, doors should be installed at 2 meter centres to provide adequate access for cleaning. (DW172 Section 18.14) The test standard BS EN 1366-1 incorporates access doors into the test method, specifically prescribing the location of the access door in each test type and orientation.  The maximum size tested is the maximum size permissible in the system.

Lindab Thor Duct ® supplies fire doors and you can even order online. View full spec of fire doors here

MIchael Renaghan

Michael is an expert in fire rated ductwork

For any further questions or to ask about a CPD presentation please contact Michael Renaghan, Technical Lead at Thor Duct ®.