Passive Fire Protection

Passive fire protection attempts to contain or slow the spread of fires through the use of fire-resistant walls, floors and doors.

Here is Dublin Fire Brigade's introduction to some of the key elements of passive fire protection based on the Building Regulations' technical guidance documentation.

Fire Compartmentation

Fire compartmentation is the separation of compartments within a building using fire safe walls and doors. It is a vital part of any fire safety design and its benefits include:

1. Prevention of the rapid spread of fire, which could trap occupants in a building.
2. Reduction of the chance of a fire growing and creating danger to occupants, fire services and people within the vicinity of the building.
3. Limitation of damage caused to a building and its contents by a fire.

What the Legislation Says

The Government's Building Regulations Technical Guidance Document B for Fire Safety defines a fire compartment as: “a building or part of a building, comprising one or more rooms, spaces or storeys, constructed to prevent the spread of fire to or from another part of the same building, or adjoining building".

It also explains that fire-resisting walls and floors are used in the separation of one fire compartment from another.

The degree of sub-division that should be provided by fire compartmentation will depend on four things:

1. The use of the building.
2. The fire load of the building.
3. The height of the building.
4. The availability of a sprinkler system.

Requirements for Fire Compartmentation

The following is a brief synopsis of the requirements outlined in the Technical Guidance Document B on Fire Safety.

When to Use Compartment Walls and Floors

• A wall common to two or more buildings should be constructed as a compartment wall.
• They should be used to separate parts of a building used for different purposes or tenancies.
• They should also be used to separate areas of special fire risk from other parts of a building.
• They must form a complete barrier between the compartments they separate and have the appropriate fire resistance and be constructed in accordance with the relevant Irish/European guidelines.

Compartment Walls

• Compartment walls that are common to two or more buildings should run the full height of the building in a continuous vertical plane and should be constructed of non-combustible materials.
• Compartment walls should continue up to roof level and not stop at ceiling height.

Compartment Floors

• The lowest floor in a building is not required to be a compartment floor.
• In a building which is 10 metres or more, a compartment floor is required to have a fire resistance of at least 60 minutes and should be constructed of non-combustible material.
• In a building that has existing timber floors, it is possible to increase the fire resistance of the floor by adding fire resistant layers beneath the existing floor covering or by filling the voids between the floor surface and ceiling below with a suitable material.

Openings Between Compartments

Openings in separating walls that are common to two or more buildings should be limited to the following:

1. A door which is needed to provide a means of escape in case of fire and which has the same fire resistance as that required for the wall and fitted in accordance with the provisions of Appendix B of Technical Guidance Document B.
2. The passage of pipes that meet the provisions of Section 3.4 of the Technical Guidance Document.

Openings in other types of compartment walls or compartment floors should be limited to those for:

1. Doors that have the appropriate fire resistance and are fitted in accordance with the provisions of Appendix B of the Technical Guidance Document.
2. The passage of pipes, ventilation ducts, chimneys, appliance ventilation ducts or ducts encasing one or more flue pipes which meet the provisions set out in section 3.4 of the Technical Guidance Document.
3. Refuse chutes of non-combustible construction.
4. Protected shafts which meet the relevant provisions.
5. Atria designed in accordance with BS 5588 Part 7 ”Fire precautions in the design, construction and use of buildings. Code of practice for the incorporation of atria in buildings”.

 

Fire Doors

The function of a fire door is to protect escape routes and the contents and structure of a building. They do this by limiting the spread of smoke and fire.

When a fire door is specified, the complete door assembly is being referred to. This includes:

• Door leaves.
• Door frames.
• Hinges.
• Latches.
• Closers.
• Intumescent strips.
• Smoke seals.

The complete fire door assembly is required to conform with Irish and European standards.

Fire doors are rated based on their ability to resist penetration by flames and hot gases. The rating relates to the time during which the integrity is held. So, for example, a door with E30 or FD30 satisfies requirements for 30 minutes and normally has intumescent strips fitted.

Where door assemblies are additionally prescribed as having an “S” rating, such as FD30S, this means that the door shall be fitted with smoke seals. It is normal for doors to be fitted with intumescent backed smoke seals. You'll find more detailed information on fire door requirements in Appendix B of the Technical Guidance Document.

 

Fire Resistance

The fire resistance of an element of construction is a measure of its ability to withstand the effects of fire in one or more ways. This can include its:

• Resistance to collapse or its ability to maintain load-bearing capacity.
• Resistance to fire penetration or its ability to maintain the integrity of the element. This applies to fire separating elements of a building.
• Resistance to the transfer of excessive heat or its ability to provide insulation from high temperatures. This also applies to fire-separating elements of a building.

The measure of an element's ability is usually expressed in terms of time. For example, something can have 30 minutes fire resistance, 60 minutes fire resistance and so on.

Factors that Impact Fire Resistance

Several factors have a bearing on the fire resistance of a building, including:

• Fire severity.
• Building height or depth.
• Building occupancy.
• Intervention by firefighters.

Periods of Fire Resistance

Minimum periods of fire resistance are outlined in Appendix A and B of Technical Guidance Document B. However, periods of fire resistance are subject to building regulations approval as granted through the fire safety certificate application process. It is possible that the building control authority will impose a higher standard of fire resistance rating than those recommended in the technical guidance document.

Other interested parties may have legislative control over certain premises and may need to be consulted before any works are undertaken. This will depend on the use of the premises. Potential interested parties include:

• The HSE.
• The Environmental Health Department of the relevant local authority.
• The Petroleum Licensing Officer within Dublin Fire Brigade.
• The insurers of property.
• Authorities responsible for the likes of intoxicating liquor licences, public dance licences, gaming and lottery licences, including Dublin Fire Brigade.
• The conservation department of the relevant local authority.

Applying Fire Resistance

An ‘element of structure’ is a piece of construction that normally performs an important function within a building, for example a load bearing wall, a ceiling, a separating wall, or a floor.

When a requirement or recommendation is made for an existing ‘element of structure’ to be made fire resistant, the materials should be applied to the ’risk’ side of the wall, floor or ceiling. For example, if a kitchen is to be separated from the adjoining accommodation, the fire resistant materials should be applied on the kitchen side of the wall. Likewise, if a cupboard under the stairs is to be made fire resistant, the interior of the cupboard should be lined with fire resisting materials.

Where pipework or other services pass through a fire resistant structure, it is essential to ensure that all gaps are sealed with fire resisting material, such as plaster. This helps prevent the passage of fire, smoke and other products of combustion to adjoining rooms or buildings.

Adequate fire resistance can be maintained by sealing pipe openings with the likes of pipe collars and intumescent sealants.

Fire Resistant Walls and Doors

Walls that are required to be fire resistant must extend from true floor to true ceiling and have no openings.

Suitable materials for these walls would include brick, block work or stud work partitioning with a 12.5mm thickness of cement plaster. Alternatively, fire resisting plasterboard on each face of the stud work with joints taped, filled and given a plaster finish to cover exposed nail or screw heads and jointing material could be used.

For fire resistant doors, you must ensure:

• The door and its frame should be fitted as one complete unit and tested to BS 476: Parts 22 and 31 or IS EN 1634 Parts 1 and 3.
• If required, the door or frame can be fitted with an intumescent strip and cold smoke seal on all four sides. Fire door manufacturers' guidance on maximum gaps should also be adhered to but, where smoke seals are fitted, the gap at the base of the door should not exceed 3mm.
• The door fixings and hardware should be suitably fire resisting and the door closure device should be in accordance with IS EN 1154.

Fire Resistant Floors and Ceilings

Floors and ceilings can be made fire resistant by applying fire resisting materials to either the underside of the ceiling or to the floor above. Materials applied to the ceiling can include a minimum of 12.5mm plasterboard with joints taped, filled and covered with a plaster finish. Alternatively, a minimum of 9.5mm plasterboard with at least 10mm lightweight gypsum plaster finish can be used.

An alternative method of fire resistance is often chosen when an existing ornate lath and plaster ceiling is to be maintained. For this to be effective, it is essential for the existing ceiling to be 15-22mm plaster on striated wood or reed lath. It must also be in sound condition.

To assist in preventing ignition sources from entering the area between the ceiling and the floor above, boarding should be applied to the floor. This should be 3.2mm standard hardboard Type S in accordance with IS EN 13501 Part 1 - or 4mm plywood - nailed at not more than 150mm centres on the line of joints. The joints should coincide with the line of joists.

Alternatively, a suitable fire resistant material may be positioned below the floor boards instead of the hardboard described above.

The Use of Glazing

Glass may be incorporated in walls and doors providing that the construction complies with BS476 Part 22. Glass provided in isolation cannot be accredited with any particular level of fire resistance, so consideration must be given to the construction as a whole to determine its level of resistance.

Manufacturers of glass and glazed screens should be able to supply details on whether a particular construction, like screens or doorsets, can meet the necessary standards.

Fire resisting glass is categorised as 'insulating' or 'non-insulating'. Table A4 of Technical Guidance Document B limits the use of ‘non-insulating’ glazing in certain locations.

 

Additional Resources

The above methods are just some examples of effective ways to achieve a level of fire resistance in your buildings. There are many other ways of achieving a similar standard.

For more information, check out the resources below for more detailed guidance and more extensive options for implementing Passive Fire Protection in your buildings:

Department of Housing, Local Government and Heritage

• Technical Guidance Document B – Fire Safety.
• Fire Safety Management in Places of Assembly.
• Fire Safety in Flats.
• Fire Safety in Gaeltacht Households.
• Fire Safety in Preschools.
• Fire Precautions in Existing Hotels, Guesthouses and Similar Premises.
• Fire Safety in Guest Accommodation.
• Fire Safety in Hostels.
• Fire Safety in Nursing Homes.

National Standards Authority of Ireland

• IS EN 1364-1:2015: Fire Resistance Tests for Non-load bearing Elements Part 1: Walls.
• I.S. EN 13501-2:2016: Fire classification of construction products and building elements part 2: Classification using data from fire resistance tests, excluding ventilation services.
• IS EN 1634-1:2014: Fire resistance and smoke control tests for door, shutter, and openable window assemblies and elements of building hardware - Part 1: Fire resistance test for doors and shutter assemblies and openable windows.
• IS EN 1634-2:2008: Fire resistance and smoke control tests for door, shutter, and openable window assemblies and elements of building hardware - Part 2: Fire resistance characterisation test for elements of building hardware.
• IS EN 1634-3:2004: Fire resistance and smoke control tests for door, shutter, and openable window assemblies and elements of building hardware - Part 3: Smoke control test for door and shutter assemblies.

British Standards Institution

• BS 476 : Part 20 Method for Determination of the Fire Resistance of Elements of Construction (general principles).
• BS 476 : Part 21 : Methods For Determination of the Fire Resistance of Load Bearing Elements of Construction.
• BS 476 : Part 22 : Methods For Determination of the Fire Resistance of Non-Load Bearing Elements of Construction.
• BS 476 : Part 23 Methods for Determination of The Contribution of Components To the Fire Resistance of a Structure.
• BS 9999 Code of practice for fire safety in the design, management and use of buildings.
• BS 9991: Fire safety in the design, management and use of residential buildings. Code of practice.
• BS 13501: Part 1 +A1: Classification using data from reaction to fire tests.
• BS 8214 Code of Practice for fire doors with non metallic leaves.
• PD 6512 : Part 3 : Guide to The Performance of Glass.

Contact Dublin Fire Brigade

If you need advice or are concerned with the fire safety features of your building, such as fire doors, alarm systems or escape routes, contact our Fire Prevention Duty Officer using the details below.