These questions and answers are designed to provide guidance and it is suggested that the reader
looks through these in the first instance before calling the ASFP, as it is likely that they will address his/her particular situation or problem.

The following questions often provide links to other websites and documents.  In some cases registration is required before information or documents can be accessed.

A ASFP General
B Built In Fire Protection
C Reliable Information
D Regulations
E Product and Installer Certification
F Structural Steel Fire Protection
G Steel and Reactive Coatings
H Steel and Fire Protection Boards or Sprays
I Reaction to Fire
J Roofs
K Concrete Floors
L Regulatory Reform (Fire Safety) Order
M Cast and Wrought Iron
N Fire Resisting Ducts
O Fire Stopping Applications

A1. What is the ASFP?
Formed in 1975, the ASFP is the trade association that represents the interests of the UK’s manufacturers and installers of fire protections systems for steel, concrete, ductwork, dampers, penetration seals and fire stopping. These systems are sometime referred to as passive fire protection products. For a list of ASFP members click here
A2. What does the ASFP do?The ASFP works with Government and standard setting bodies both directly and via other sector group associations to increase the quality of the installed fire protection of the UK’s buildings and industrial plants including onshore as well as offshore facilities.
A3. Who does the ASFP work with?

The Passive Fire Protection Federation (go to which is the sector group for the entire passive fire protection industry, and includes apart form the ASFP the trade associations that are involved with fire doors, fire shutters, fire resistant glazing and partitions. Regulators, enforcers, insurers, test houses, certification bodies and other professional institutes are also members of the PFPF.

The European Association for Passive Fire Protection  which provides the ASFP with a route into the European standard making scene.

The National Specialist Contractors Council (go to which represents the interests at Government level of specialist contractors.

The Construction Industry Training Board (go to The ASFP participates with the CITB in the design of training courses, National Vocational Qualifications and Apprenticeships

B1. What is fire resistance?The fire resistance of a component, such as a steel column, is its ability to resist the affects of fire for a period of time and this is usually measured by submitting the component to a firetest as defined in a nationally or internationally recognised standard. 
B2. What is passive fire protection?Most construction materials have some natural resistance to fire and as such comprise built-in fire protection. This natural fire resistance may be enhanced by the use of added materials or systems that are known by the collective term of passive fire protection. For example the fire resistance of steel may be enhanced by the use of intumescent coatings, and concrete by sprayed cementitious coatings. While holes in partitions around penetrating services may be sealed by proprietary mortars or batts.
B3. Where will I find information concerning passive fire protection products other than those manufactured and installed by ASFP members?At the website of the Passive Fire Protection Federation (go to you will find links to the trade associations that are involved with fire doors, fire shutters, fire resistant glazing and partitions.
B4. Why does steel need fire protection?Under load steel will start to buckle and move when temperatures reach 550 C and in a steel framed building this will compromise its stability and compartmentation.
B5. Where can I find listings of independently validated products for the fire protection of structural steel?

The ‘Yellow Book’ (also known as ‘Fire Protection for Structural Steel in Buildings’) contains such listings and is available as a free download from this website, click here 

B6. Why do service penetrations/openings through fire rated walls need sealing/stopping?

Because hot gases, fire and smoke will pass through thus spreading the fire and consequently the threat to life.

B7. What Guidance is available for the routine maintenance of fire protection systems?

The ASFP strongly advises building owners/users to ensure the routine maintenance of fire safety measures in buildings, arising from specific duties as defined in the Regulatory Reform (Fire Safety) Order 2005 – summarised in PowerPoint slides available elsewhere on this web site.

There is no generic guidance available as maintenance will depend on the product sector, the working environment and service conditions; consult the fire protection manufacturer for advice for the maintenance of specific products.

In the case of structural steelwork, if refurbishment or upgrading of the fire protection is required, the ASFP publication TGD 10 may be helpful. Click here 

C1. Where can I find listings of independently certified products that are suitable for sealing/stopping penetrations/openings?

The ‘Red Book’ (also known as ‘Fire Stopping and Penetration Seals for the Construction Industry’) contains such listings and is available as a free download from this website, click here 

C2. I have a fire protection problem for which there appears to be no tested passive fire protection system, what can I do?

The Passive Fire Protection Federation has a document entitled ‘Guide to undertaking assessments in lieu of fire tests’ and this gives guidance for the situation you describe.

C3. Is there a publication which will take me through the processes involved with the specification, installation and maintenance of passive fire protection systems?Yes the ASFP has a document, which was partly funded by the Department of Trade and Industry, entitled ‘Ensuring Best Practice for Passive Fire Protection in Buildings’ and this can be downloaded by going to the publication page.
D1. Who sets the level of passive fire protection in a building?

Generally the Building Regulations for new build. The Fire Authority has to be consulted if refurbishment projects are to be undertaken.

D2. What is Approved Document B (ADB) to The Building Regulations for England and Wales?

ADB is a Fire Safety document that provides practical guidance on meeting the requirements of the Building Regulations. There may also be alternative ways of achieving compliance with the requirements of the Building Regulations. For a copy of Approved Document B click here

D3. But I live in Scotland, what documents are available from the Scottish Executive?

Technical Standards for fire performance of buildings are available from the Scottish Building Standards Agency at

Details on Scottish fire safety legislation is available

D4. But what about Northern Ireland?

Go to for Part E Fire Safety of the Building Regulations (Northern Ireland) 2000 to see how compliance may be achieved.

D5. I understand that in the UK Building Regulations with regard to fire are aimed mainly at saving life. If I want to go further and install extra passive fire protection to enhance the preservation of the building in a fire situation where can I find information?

The Fire Protection Association and the Association of British Insures publish a document called ‘ The LPC Design Guide for the Fire Protection of Buildings’ and this will give you guidance with regard to increasing the level of passive fire protection in your building. For a free download click here 

E1. Third Party Certification Schemes

Why should I use a third party certificated contractor to install passive fire protection systems?

Approved Document B (Fire Safety) to the England and Wales Building Regulations states “Since the fire performance of a product, component or structure is dependent upon satisfactory site installation and maintenance, independent schemes of certification and registration of installers and maintenance firms of such will provide confidence in the appropriate standard of workmanship being provided.

E2. Where can I find information concerning third party certificated schemes for installers of passive fire protection systems?

The following companies are known to provide such schemes:-

LPCB – go to

FM Approvals go to

IFC Certification Ltd – go to

Intertek Testing & Certification Limited – go to

Underwriters Laboratories UK Ltd – go to

Warrington Certification Ltd – go to

F1. Structural Steel Fire Protection

How do passive fire protection products protect structural steel?

For a general overview please go to

F2. Can you have Hollow Section Beams acting compositely with a slab?

You can use hollow sections in composite construction provided the manufacturer has undertaken a loaded hollow beam test for the appropriate fire resistance period and has had an assessment supported by a temperature analysis for the appropriate limiting temperature or a lower temperature.

Where the concrete slab is formed with profiled metal floor decking, either the voids are filled, or the top flange is protected.

As the top flange must be protected or the voids filled – no extra protection is required and the percentages in Table 18 of 4th edition of the Yellow Book are not applicable.

Is it practical to add weld studs to the top of Hollow Section Beams?

Studs can be applied using welding but installation of welded studs after an intumescent coating is not recommended as the heat caused by the welding process may cause the coating to react.  Where an intumescent coating is already in place, on any surface of the section, then the use of shot fired studs are recommended.

Welded studs can be added to the top of unpainted hollow section beams provided that there is a minimum thickness of steel to which the stud is welded, typically 40% of the stud diameter e.g. 19mm stud implies 8mm (7.6mm) steel thickness.

G1. I have specific questions with regard to the use of intumescent coatings for structural steel fire protection can you help?

Can intumescent paints be used for the fire protection of beams at the heads of compartment walls or fire resisting walls?

A generic answer  can be provided. Yes, intumescent coatings can usually provide the necessary structural fire protection to the steel beam/section.

N.B.Where any fire separating wall forms a junction with the steel structure, there may also be a need to satisfy the fire integrity and insulation criteria of the entire fire wall division, so additional protection may be required to the steel section to meet these additional criteria, and/or to address any firestopping requirement between the junction of the protected steelwork and the wall itself.

Where the steel beam is at right angles to the fire resisting wall, additional firestopping is likely to be required to close the path to passage of fire in any space created in the web of the steel beam, and above or below the beam.
For any further guidance on fire integrity and insulation criteria consult Building Control.

G2. Can intumescent paints be used to protect beams and columns where external cladding systems are intended to be abutted to the steel surfaces?

In general, a minimum gap of 50  x dry film thickness of the reactive coating is recommended to allow adequate expansion in a fire, This guidance applies to the gap between the cladding and the flat surfaces of the protected steel section,  as well as the flange tips unless specific fire tests prove otherwise.

Gap sizes may be reduced where manufacturers have specific fire test evidence.

Continuous linear fixings [timber or metal] should be considered as part of the main beam, and duly protected from fire., unless other supporting fire test evidence can be provided.

G3. Brackets and angles are often added to perimeter steel beams to allow cladding systems to be fixed to the structural framework. What is the recommended treatment of these angles and brackets so that the fire resistance of the beam is not inadvertently reduced?

Continuous linear fixings should be considered as part of the main beam, and duly protected from fire.
The mass, spacing and orientation of fixings can all play a part in the total potential heat transfer into the steel structure. The effect from the heating of brackets fixed at intervals to different masses of steel structure is very difficult to quantify. It is not possible to give generalised guidance on the effect of spaced fixings to steelwork protected by reactive coating products.  The intumescent coating manufacturer should be contacted for specific advice. Fire protection may well be advised.
The manufacturer of the intumescent coating should be contacted for advice on the extent of any fire protection onto the cladding beyond its junction with the fixing bracket.

G4. What clearance is required between the steel sections coated with intumescent paints and any services penetrating through apertures in the web of  protected steel sections?

No generic answer can be provided.
Consult individual intumescent paint manufacturers for advice.

G5. In the case of deep web beams, the deepest web that is fire tested is 610mm and the steel section  is not loaded when tested. Does this mean that the tested intumescent paint can be used to protect any steel with a deeper web depth, with or without additional retention of the coating by mesh systems? Do any limitations apply?

Guidance is given in Draft prEN 13381-8 Reactive Coatings as follows:-
Provided that one of the beams tested has a web depth of at least 600mm there will be no limitation on the maximum web depth that can be protected, otherwise the assessment will be limited to the maximum web depth tested plus 50%. The intumescent coating manufacturer should be asked to comment on any limitations or reinforcement.

G6. Most new steel frames need to be fire protected before the external envelope is added to the building stucture, whilst adequate space exists. The protected steelwork may therefore become exposed to the weather elements for a time. Is this a problem for intumescent coatings?

Intumescent coatings are available for all types of service environments when used in conjunction with the correct topcoat system.
However, there is no generic guidance available. Consult individual manufacturers for advice

There are many ways of demonstrating durability of intumescent products. The obvious and most important is track record of real projects over many years. In addition some products have been tested to BS 8202 Part 2.
Underwriters Laboratory have a range of environmental testing requirements for both internal and external uses.
Most recently the European Technical Approval Guidance for intumescents (ETAG 18 Part 2) also has specific durability testing depending on service conditions.

G7. Does the passage of time effect the ability of intumescent coatings to develop char when subsequently exposed to fire?

As in Q6 there are many standard aging test requirements in the national and European requirements previously mentioned.
There is no generic guidance available. Consult individual manufacturers for advice.

G8. What is the effect when steel sections protected by intumescent paint systems are overpainted by a ‘house proud’ client or  building management team?

Some manufacturers have a range of fire test data where multiple topcoats have been applied prior to fire testing. It may be possible to overpaint certain intumescent coating systems.
Consult individual manufacturers for advice.

G9. Can intumescent coatings be used to protect cellular beams

Yes, in the case of cellular beams with circular holes – Refer to the fire test protocol as detailed in Section 6.2 of the ASFP publication ‘Fire protection for structural steel in buildings’ – 4th Edition 2007. This publication can be downoaded from the publication page free of charge.

In the case of  cellular beams with other shaped apertures, refer to the manufacturer who must provide specific third party verification of the performance

‘Information is also provided in Technical Guidance Document 09: Code of Practice for the fire protection of steel beams with web openings. This document can be downloaded free of charge from the ‘publications’ section of this website

G10. Is fire protection required for steel  bolt  heads connecting steel sections?

Yes bolt heads should have the same resistance to fire exposure as the steel section, unless the fire protection manufacturer can demonstrate otherwise through third party verification of the performance.

G11. Can I spray another coat of  intumescent paint over a system which already has a top coat?

Generally this is not advisable unless the coating manufacturer has relevant fire test data.  The applicator MUST first consult the manufacturer of the coating system. It is likely  that the manufacturer will advise full removal of the top coat before re-application.

G12.Can fire test data obtained from circular hollow steel (CHS) sections be used for the fire protection of solid steel bars or rods?

Fire protected solid steel bars may behave differently from fire protected hollow steel sections in fire. The use of a specific protection system and its thickness should be based on a proven capability suitable to the application.

In June 2011, the ASFP Technical Committee published Advisory Note No.4 – Test and Assessment Procedures for Circular Solid Rods Protected with Intumescent Coatings which details a fire test protocol for assessing the fire protection for solid steel bars and rods. This is available here

H1.When intumescent coatings are applied over other types of passive fire protection, such as boards or non-reactive sprays, or a different intumescent coating, are the individual contributions to fire resistance additive?
Definitely not. We do not advise mixing fire protection systems of any type unless there is specific test evidence available from the manufacturers concerned. Combinations of individual fire resistance periods are not additive in any circumstances, unless supported by relevant test information.
H2. I have specific questions with regard to the use of sprayed cementitious coatings or boards for structural steel fire protection can you help?

How do we protect deep web beams ?

Fire protection board systems may be applied in a boxed or profiled configuration.

[1] For profiled board applications,
Flexible boards such as those made from mineral wool may require cover strips at all joints.
The use of rigid boards in this situation is generally not practical.

[2] For boxed board applications,
The use of solid or “T-shaped “ noggings will usually be required on all beams with web depths of 533mm or greater. Contact the manufacturer for specific requirements.
Flexible boards may require more internal support and cover strips at joints than rigid boards. Contact the manufacturer for specific requirements.
Rigid boards are more self supporting but may require protection to the web joint or secondary support. Consult the manufacturer for specific requirements.
Fire protection cementitious spray applications will require the use of retention mesh where the web depth between the flanges exceeds 650mm. Consult the manufacturer for fixing details.
Note: mesh retention is also required where flange width exceeds 325mm.

H3. How do we protect beams with multiple web openings?

The section factor of the steel beam is established using the equation 1400/t where t is the thickness (mm) of the lower part of the steel web-post. The thickness of the fire protection system to be applied is then calculated based on the limiting temperature of the beam and a further 20% is added to the thickness.
Unless specific product data exists, protect all edges, dependent on the fire protection period required.
Further guidance is provided in Section 6.1 ASFP publication “Fire protection for structural steel in buildings. 4th Edition”

Information is also provided in Technical Guidance Document 09: Code of Practice for the fire protection of steel beams with web openings. This document can be downloaded free of charge from the ‘publications’ section of this website

H4. How do we deal with columns and beams within and passing through compartment walls?

Where a beam is passing through a compartment wall it should be fire protected to the appropriate level up to the wall and a fire seal should be utilised to prevent passage of fire through the compartment where the beam meets the wall. This fire seal should provide the necessary level of fire resistance, including fire integrity and insulation, and should be capable of dealing with any expected differential movement.

Where a beam or column forms part of a fire compartment wall there are two separate issues,
[a]  fire protection of the steel
[b] fire separation criteria for the wall.

The criteria for [b]may be the dominant feature, such that additional protection thickness/measures will then be required for the steel work in the region of the wall, in order to deal with the fire integrity and insulation requirement from Approved Document B – Appendix A.
Specifically, under normal circumstances, a maximum 140ºC rise in the average temperature of the surfaces on the non- fire side of the compartment wall will be permitted. This is to be contrasted with keeping steel temperatures below 550ºC or so to maintain the structural load-bearing capability of the steel.

In the case of non load-bearing walls consideration should be given to the deflection of the beam during fire and the effect that this may have on the integrity of the compartment wall.

Guidance on the fire protection of partially exposed steel members can be found in Section 1.63.ASFP publication “Fire protection for structural steel in buildings. 4th Edition”

H5. How do we address the issue of brackets and angles fixed to columns and beams?

Where brackets, angles and other secondary fixings are to be attached to a steel beam, or column, the passage of heat into the structural steel via these fixings must be kept to a minimum. In order to achieve this fire protection of the fixing may be required. Consult the fire protection system manufacturer for specific details.

Where fixings are installed prior to the fire protection:

1) Boards can be cut to fit around them.
2) In the case of cementitious sprays, the fixings should be masked and then the spray may be applied in the normal way and the masking removed afterwards to reveal the fixings.

If fixings are installed after the fire protection system then areas of fire protection, of a minimum size, can be cut away to allow the fixings to be attached. A patch repair may be required in some circumstances to reinstate the required level of fire resistance.
Contact the fire protection system manufacturer for specific requirements and procedures.

H6. How do we deal with deflection at interfaces of steelwork with non load-bearing walls?

The limits of deflection are described in the guidance provided in Approved Document B – section 8.2.7, in support of the UK  Building Regulations
This guidance will limit the steel deflection and allow the partition supplier to provide an interface detail.

H7. What primer systems are compatible with spray applied fire protection?

Gypsum based products are generally less chemically aggressive than those based on cement.

Where cement based products are applied to primed steel, an epoxy type primer will generally be compatible whereas an alkyd based primer will not be compatible.

Cementitious sprays are often applied to bare steel.

It is essential that installers and the designer consult with the cementitious spray manufacturer to confirm the compatibility of any steel priming system.

H8. How do we protect steel beams supporting timber joists or concrete slabs?

Where timber joists are located into the web of a beam the steel beam will usually need protection from fire in order to comply with the requirements of Approved Document B Appendix A. The timber joists which penetrate through the fire protecting layer must be fire stopped with a tested method or appropriately fire tested penetration seal. Consult manufacturer for specific guidance.

In addition, the timber floor will need to be fire resisting to the appropriate level and fire protection to the timber floor and timber joists may be required. The methods used to fix any fire protection system to the timber shall be as tested in a relevant fire test.

The fire protection of concrete slabs will depend on [a] the construction, density, the thickness, the thickness of concrete over reinforcement steel, the fire resistance requirements for the concrete floor slab, and [b] the thermal requirements arising from the location of the slab in the building.
Consult the manufacturer for specific guidance.

H9. Does steelwork (columns, beams, etc) in boundary wall condition require full protection?

The fire resistance requirements of the wall may change according to the requirements of Building Regulations Approved Document B 2006, and particularly where the building wall is less than 1 metre from the boundary of the property.

The requirements for the fire resistance criteria of the boundary wall must be ascertained in order to assess any additional requirements for the structural steel associated with the boundary wall.

Consult the manufacturer for specific guidance

I1. What is the difference between Class 1 and Class O Spread of Flame classifications?

See TGN 5 Guide to Class 0 and Class 1

To access these click here 

J1. How do I use passive fire protection products for roof components and secondary steelwork of portal framed buildings?

See TGN 4 Fire protection of roof components and secondary steelwork of portal framed buildings

To access these click here 

K1. Can I upgrade the fire protection of a concrete floor using passive fire protection products?

Yes see TGN 1 Spray Coatings for fire protection of concrete floors

To access these click here 

L1. What is the Regulatory Reform (Fire Safety) Order?

Click here for more information

M1. Cast and wrought iron

Can fire test data obtained from mild steel be used to determine fire protection thicknesses for cast and wrought iron?

ASFP are of the opinion that data obtained from mild steel fire tests can be used to provide protection thicknesses for cast iron and wrought iron using the same limiting temperatures, subject to the conditions referenced in the following reports [a] and/or [b]
[a] BCIRA Report ‘Cast iron in building structures – revived interest in a proven case’ by E.R.Evans dated November 1984.
Further information can be obtained from:-
Castings Technology International, Advanced Manufacturing Park, Brunel Way, Rotherham S60 5WG. T: +44 (0)114 254 1144, E:

[b] ‘ Historic buildings and fire performance of cast iron structural elements’  by J R Barnfield & A M Porter

NOTE that the Structural Engineer must establish the Section Factors and be satisfied with the integrity of the iron work before specifing fire protection.

N1. Fire Resisting Ducts

What action is needed where fire resisting ducts pass through oversized openings in fire resisting elements of construction?

ANSWER. Any oversized gap shall be reduced in size such that the additional fire penetration seal around the duct can function as fire tested within a maximum residual opening.

Responsibility for the satisfactory performance of each element of building construction (e.g. walls, floors, cavity barriers, etc.) lies with the installer of each particular element. The ‘change over’ of responsibility occurs at the interface between the fire resisting ductwork and the elements. It is imperative that the interface detail does not compromise the fire performance of either the element of building construction or the fire rated duct. The building designer, mechanical services designer and the installer all have a responsibility to pay ‘due care’ to this detail.

Further details are provided in ASFP ‘Blue Book’ publication ‘Fire resisting ductwork – 2nd Edition, Section 7, click here 

N2. Can I suspend a fire-resisting ductwork system from any structure that is not fire resisting for an appropriate period?ANSWER – In general the answer is no, especially in the case of ductwork used for smoke extraction.

Any such mounting is likely to compromise another essential function of the ductwork system, where it passes through a fire resisting element of constructions, unless other proven measures have been incorporated to mitigate such an effect.

N3. Is it permissible to allow other services to be supported from the same duct support system?ANSWER – This may be possible to accommodate at the time of installation, providing that a risk assessment determines that stresses on the hanger cannot go beyond that of the tested product. For example, this could include the potential effect of extra load arising from collapse from the secondary service.

Consultation should always be made with the system manufacturer/supplier. See ASFP ‘Blue Book’ publication ‘Fire resisting ductwork – 2nd Edition sections 6.1.2 note 2 and

N4. What actions should be taken when improper fire resisting duct mounting is evident?ANSWER – Ordinarily, contact the installation contractor and confirm that there has been relevant fire testing and competent assessment on the system. If there is no satisfaction then contact the main contractor/employer/CDM Coordinator to raise any concerns. Ultimately contact the local enforcing authority.

Approved Document B Appendix G summarises the legal duties on contractors arising under Regulation 16B to ensure that users of building [responsible persons] can make a relevant risk assessment as required under the Regulatory Reform (Fire Safety) Order 2005.  Observers have a Duty of Care.

N5. Does fire resisting ductwork require any fire insulation criteria in all circumstances?ANSWER – When the specification is for a prescribed period of fire resistance then all fire resistance criteria shall apply, in terms of the load-bearing capacity (stability), integrity and insulation criteria. Removal of the insulation criteria shall only apply in exceptional circumstances

It is a requirement that where these compartment walls/floors are penetrated by ducts or other building services, the fire performance criteria for the penetrated wall or floor are maintained, such that fire in one compartment may not spread to other areas.

In specific installations, Building Control authorities may waive the insulation requirement or allow a reduced period of insulation, Examples include some car parks, where enforcers have considered that there was not a possibility of combustible materials being in close proximity of the ductwork.

N6. What supports and fixings to building structure should be used for fire resisting ducts?ANSWER – The supports used must be as fire tested in the ductwork system. Because of the way duct supports are fixed or anchored in fire tests, alternative fixings are permitted provided that suitable test evidence is available to justify the use on the intended duct system.

Further information is available in ASFP ‘Blue Book’ publication ‘Fire resisting ductwork – 2nd Edition’ at section and 7.2

N7. What is meant by ‘field of application’ of test results for fire resisting ductwork?ANSWER – The answer comes in two parts. DIAP and EXAP rules are an output from European harmonization of fire testing methods and classifications. At a national level, experienced persons or fire test organisations have previously provided assessments of expected performance based on expert judgement.

[a] The direct field of application (DIAP)

DIAP rules are provided in BS EN 1366 test standards. They are derived from information obtained from tests carried out in accordance with relevant EN 1366 tests at recognised laboratories in Europe.  The test results achieved by a particular design may be directly applied to a limited number of variations (e.g. a reduction in duct size) without recourse to expert advice, providing the design remains substantially as tested.

The scope of the current BS 476 test method does not consider the effect, detrimental or not, that variations in the test construction may have on the achieved performance of the duct.  The test result only applies to the tested design and size; the field of direct application is very limited. The ASFP ‘Blue Book’ publication ‘Fire Resisting ductwork – 2nd Edition’ contains information in Section 6.

[b] The extended field of application (EXAP) rules are derived from test evidence to relevant BS EN 1366 test standards and is provided in the relevant section of BS EN 15080. EXAPs shall be based on primary test evidence to BS EN 1366 and may be supplemented by appropriate test evidence generated from other sources, or other relevant historical data.

The EXAP rules consider changes in the tested design beyond the scope of direct application and may also consider variations to the tested design.  For example, an increase in duct size which necessitates the inclusion of a joint in the duct walls.

At a national level, for the purpose of assessments for the extended field of application, laboratories accredited by UKAS for conducting the relevant tests might be expected to have the necessary expertise or competent authority/persons appropriate to the complexity of the evaluation undertaken.

N8. What considerations are needed for access panels in fire resisting ductwork systems?ANSWER – Access panels are frequently fitted to fire resisting ductwork for purposes such as cleaning or access to dampers.  The panels are fitted in the walls of the duct but must not interrupt the duct structure, e.g cross joints, stiffeners and supports.  Ideally the access panel will have been tested as part of the fire resisting ductwork system.  The test must have demonstrated that the design of access panel is able to maintain the required fire performance requirements of the ductwork system without weakening the structure of the duct.  The maximum size of panel is that tested.

Proprietary access panel systems are available.  To be acceptable for use as part of a ductwork system they must have been shown by test to be capable of maintaining the required fire performance requirements of the ductwork system when mounted in a similar type of duct.  The access panel assembly includes the panel, the mounting frame, the fixings holding the panel in the frame, the fixings fastening the mounting frame to the duct and any seals.

N9. What effect will arise from variations of duct geometry and orientation on test results?ANSWER
[a] A test result for fire resisting horizontal ducts is applicable to horizontal ducts only.[b] A test result obtained for fire resisting vertical ducts is applicable to vertical ducts without a horizontal branch.[c] However, for fire outside ducts, if a test is successfully made on a horizontal duct with a branch, for a stated period of fire resistance, then vertical ducts may include a horizontal branch for that same period of fire resistance.[d] For a rectangular duct, the maximum aspect ratio between the longer and shorter sides is 4:1
N10. Can test results for rectangular ductwork be used for circular or flat oval ducts; circular or flat oval ‘spiral wound’ ducts; and flexible ducting systems?ANSWER – The answers are different for those ducts tested to BS 476 Part 24 or tested to BS EN 1366 test methods.

In the case of BS 476 Part 24 test data, circular and flat oval straight seamed and spirally wound steel ducts may be assessed on the basis of the tests on rectangular ducts. Details of the construction of circular and flat oval, straight seamed and spirally wound steel ducts must be provided by the duct manufacturer. Further details are provided in ASFP ‘Blue Book’ publication ‘Fire resisting ductwork – 2nd Edition Section’

In the case of BS EN 1366 test data, no equivalence is permitted and all ductwork systems must be individually tested. The published European DIAP and EXAP rules apply.

As the vast majority of fire tests on ducts are conducted with rigid ducts it is not appropriate to extrapolate this data for flexible ducts. Therefore, unless the flexible duct system has been fire tested, the guidance cannot be assumed to apply.

N11. Ductwork passing through protected escape routes

(Other than a dwelling house or within a flat)

Fire dampers only

Q. Does ductwork passing through a protected route need additional fire rating if it has been fitted with fire dampers when entering and leaving the corridor or stair enclosure?

Yes. Fire dampers are not designed to protect against smoke which is a concern for protected escape routes. A closed fire damper will still leak a considerable quantity of smoke. Fire dampers will not prevent heat conduction and radiation from distorting ductwork in the escape route and causing joints to open up and contaminate the escape route.

Therefore the ductwork itself would need to be fire resisting (tested to BS 476: Part 24 or EN1366-1 with fire exposure from the inside) and not serve the protected route.  Alternatively, it needs to be enclosed within fire resisting construction e.g. a suspended ceiling tested from above which must be smoke tight.

However, an alternative would be to use ‘dampers’ and not protect the duct – this is possible but the dampers would need to be ES classified leakage rated fire dampers. Such dampers should achieve an ES classification to BS EN 13501-3 when tested to BS EN 1366-2. These dampers are considered to have good smoke resisting properties in addition to fire resistance. Dampers tested to BS 476 cannot provide an ES classification.

For situations where ductwork serves a dwelling house or internal parts of a flat see FAQ 5 below

Source: Approved Document B 2006 Vol. 2; paragraph 5.48.


N12. Metal ductwork

Q. If I install 16 gauge steel ductwork (constructed to DW142/144) where passing through a protected route; is this acceptable as a fire resisting duct?

No. Ductwork passing through a protected corridor should be fire resisting when tested to BS 476: Part 24 or EN1366-1 (with fire exposure from the inside) and not serve the protected route for the required fire time. We have not seen any result which indicates that an ordinary steel duct would survive such a test.

DW 144 is a specification for ventilation ductwork, not for fire resisting ductwork. Only ducts tested to BS 476: part 24 or EN 1366-1 can provide fire resistance.

An alternative to using a fire resisting duct would be to use ES classified leakage rated fire dampers. Such dampers should achieve an ES classification to BS EN 13501-3 when tested to BS EN 1366-2.

Source: Approved Document B 2006; Vol. 2; paragraph 5.48.

N13. Ductwork protected by Mineral wool

Q. Would wrapping metal ductwork with mineral wool be acceptable to protect ductwork passing through a protected route as a means to fire protect the ductwork?

We are not aware of any publicly available test evidence to confirm a generic solution. However, there are proprietary manufacturer’s systems that have been tested using this approach. Any such system would need to specify the ductwork construction, fixtures and fittings, method of support etc as well as the details of the specific mineral wool. It would also need to be supported by appropriate test evidence.

N14. Ductwork having a class 0 performance

Q. Would a duct having a class 0 (or European Class B-s3, d2 or better) fire rating be acceptable in a protected route as a means to fire protect the ductwork?

A. No. class 0 (or European Class B-s3, d2 or better) does not refer to fire resistance of the duct but to how the surface of the duct, or any material applied to it, ‘reacts to fire’ i.e. if the surface material if ignited, spread flame over its surface or has a high heat release.

N15. Ductwork passing through protected stairway or internal hallway in a dwelling house flat or maisonette (for common areas in flats/maisonettes the guidance above applies).

Q. In a residential flats development, if I install 16 gauge steel ductwork (constructed to DW142/144) in a corridor which has been defined as a protected corridor is this acceptable as a fire resisting duct?

A. Inner Halls

In the case of dwelling houses or the inner hall to flats, Approved Document B 2006 Vol 1 and 2 does not require the ductwork to satisfy the BS 476-24 or EN1366-1fire resistance test. There is a deemed to satisfy requirement for the ductwork to be rigid steel construction and all joints between the ductwork and the enclosure should be fire stopped.

Therefore metal ductwork is only acceptable without any further protection if installed in the protected routes of dwelling houses or inner halls of flats.

A. Common areas

Ductwork in the common areas would need to satisfy the BS 476 Part 24 or EN1366-1 fire resistance test or be enclosed within fire resisting construction for the required period of fire resistance.

Source: Approved Document B 2006 Vol 1; paragraph 2.17.

O1. What data/documentation should I ask for to demonstrate that product X is suitable for use?

Manufacturer’s marketing information may not always include information for a particular field of application. The suitability of use is best justified by the manufacturer, by:-

The production of a valid fire test or assessment report against the requirements of BS 476: Part 20, or a European fire classification report to EN 13501-2 (when tested to EN 1366 Parts 3 or 4 as appropriate) as issued by a UKAS accredited fire test laboratory or in the case of an assessment by a competent person or body, which should adequately demonstrate the suitability of a fire stopping product for use within a specific application or a range of applications.

See ASFP ‘Red Book: Fire stopping – 3rd Edition’ section 11.3 for an expanded explanation.

O2. Should I provide fire stopping around combustible pipes which are less than 40 mm in diameter?

Yes, Approved Document B states: “If a fire-separating element is to be effective, every joint or imperfection of fit, or opening to allow services to pass through the element, should be adequately protected by sealing or fire-stopping so that the fire resistance of the element is not impaired”.

Also see 10.4.4 in ASFP ‘RED Book’ 3rd Edition”

which is accessible here

Q: How do I deal with fire-stopping combustible pipes of 40 mm internal diameter or smaller

A1. This is dealt with in Section 7 of the guidance to the building regulations in England & Wales, Approved Document B, vol. 1 for dwellinghouses, and section 10 of vol. 2, for buildings other than dwellinghouses. Similar guidance is given in the regulations for Scotland and for Northern Ireland.

A2. The guidance requires that combustible pipes of 40 mm internal diameter or smaller, which pass through fire-separating elements (unless the pipe is in a protected shaft), should meet the appropriate provisions in alternatives A, B or C below:

Alternative A: 
Provide a proprietary sealing system which has been shown by test to maintain the fire resistance of the wall, floor or cavity barrier.

Alternative B: 
Where a proprietary sealing system is not used, fire-stopping may be used around the pipe, keeping the opening as small as possible.

Alternative C: (only applicable to uPVC)
The pipe may be used with a sleeving of non-combustible pipe passing through the separating element and not less than 1000 mm long on both faces (diagram not reproduced here).

A3. It is recommended that ‘Alternative A’ be selected as the most robust solution, as many proprietary systems exist with appropriate test evidence and/or certification. ‘Alternative B’ does not require the use of a proprietary system, but also does not clarify which type of ‘fire-stopping’ should be used with respect to the varied service situations and separating elements that will be encountered. It will therefore be difficult to confidently select an appropriate non-proprietary product or material, capable of reinstating the performance of the separating element.

Also see 10.4.4 in ASFP ‘RED Book’ 3rd Edition.

O3. Under what circumstances can fire stopping include pattressed solutions?

Any system intended to be used as a pattress cover to the void behind must be proven by fire test or assessment for the intended field of application and for the required fire resistance period. Ad hoc patching will not meet all the fire resistance criteria required.

O4. A plastic service penetrates a tightly cored drilled floor slab and immediately turns through 90 degree into the horizontal plane.  However, there is no or limited space for the application of wraps, collars or sleeves?  What should be done?

Under these circumstances it will be impractical to achieve an adequate fire stop with any of the common pipe closure solutions, but this does not remove the requirement to provide such a fire stop. It will therefore be necessary to either:-

[a] reposition/extend the pipe such that a pipe collar can be fitted to the soffit of the floor or

[b] use a smaller diameter pipe so that a collar/wrap/sleeve can be fitted within the floor, or

[c] re-drill the hole in the floor, so that a collar/wrap/sleeve can be fitted within the floor, or

[d] the pipe could be boxed in by fire resisting construction, or

[e] more innovative pipe closure devices, specifically designed and tested to cope with this situation, would be required.

O5. We are making refurbishment of an existing building. The existing services are both installed and ‘live’ and the required fire resistance of a wall is increased. How should I proceed and deal with inaccessible areas?

The law requires that a relevant fire risk assessment is made and maintained to identify all potential hazards and associated risks throughout the life and use of the building, and that all actions taken are recorded. The fire resistance and or other provisions should be enhanced in accordance with regulatory requirements to reduce risks to an acceptable level. The methods used can only be determined in relation to the particular problem.

O6. I want to seal the point where a duct or pipe passes through a fire resisting wall, and need 60 minutes fire resistance.  How much product do I need?

We refer you to ASFP Red Book and 3rd party certificated data sheets for the appropriate application. The required performance and guidance on quantity shall be confirmed with the manufacturer, and installer, of the selected product.

07. Can I ‘mix and match’ components from different manufacturers, or different systems made by the same manufacturer, when installing fire stopping?

The simple answer is no. While it may be tempting to use e.g. manufacturer A’s mineral fibre batt with manufacturer B’s adhesive, the combination is unlikely to have been tested and therefore may not perform in fire as intended.

I have been told to use components from different manufacturers in a particular installation. Is there any way I can get further advice as to their compatibility?

In the absence of test evidence, the default answer is again no. While it may be possible to get an assessment from a fire consultant or test/certification body to cover such an application, such an installation may not be covered by any of the manufacturers’ warranties or after sales service.

The ASFP strongly recommends the use of third party certificated products. Such products will have a scope of application which will cover their use with other compatible components which may include products from other manufacturers.

O8. How do I deal with fire-stopping combustible soil pipes as they pass through floors?  DRAFT 7

1. This is dealt with in technical guidance to building regulations as follows:

England & Wales, Approved Document B, Section 7 of vol. 1 for dwellinghouses, and section 10 of vol. 2, for buildings other than dwellinghouses.

Scotland Technical Handbook, Fire Domestic 2010, clause, 2.2.9 Openings and service penetrations, and Scotland Technical Handbook, Fire Non Domestic 2010, clause, 2.1.14 Openings and service penetrations

Northern Ireland Technical Booklet E 2005, clauses 3.42 and 3.44 to 3.46.

2. The guidance requires that pipes passing through a fire-separating element should either be provided with a proprietary sealing system (such as an intumescent pipe collar or wrap), or be sleeved with a non-combustible pipe for at least 1m each side of the separating structure.

3. The guidance does give a third option but only for uPVC stack and branch pipes passing through compartment walls or floors in flats or when a branch pipe penetrates a wall separating dwellinghouses. In this case the stack and branch pipes must be no greater than 160mm and 110mm nominal internal diameter respectively, and form an above-ground drainage or water supply system only.

4. In the third option referred to above, the guidance states that the pipes must be located within  an enclosure which has a fire resistance of 30 minutes (integrity only) when exposed to fire from outside the enclosure. There are restrictions given on the types of materials that can be used to form the enclosure and the location of access panels. Gaps around the pipes should be as small as possible and still need to be fire-stopped where the pipes pass through the floor and the pipe enclosure.

5. It must be borne in mind that the guidance to the building regulations has been written assuming that installations, including the pipe enclosures and fire-stopping, have been fitted with good workmanship, are not damaged during the life of the building, and that every aspect of the guidance has been followed. The ASFP consider that all these conditions are unlikely to be met in practice. Therefore we strongly recommend that suitable pipe closing devices, e.g. tested intumescent pipe collars and/or wraps, are used at the penetration through the floor to prevent fire penetrating the floor. Similarly, the ASFP strongly recommend that fire tested pipe closing devices are also fitted around uPVC branch pipes that penetrate walls separating dwellinghouses.

6. Where pipe collars or wraps are used, care should be taken that any remaining gaps are fire-stopped with a suitably tested system that is compatible with the particular pipe collar or wrap that is being used.