Passive Fire Protection
Passive fire protection (PFP) is an integral aspect of structural fire protection and fire safety in a building. It attempts to contain or slow the spread of fires through use of fire-resistant walls, floors, and doors.
Fire compartmentation, or the separation of compartments in a building with fire safe walls and doors, is a vital part of any fire safety design.
Fire compartmentation has benefits:
- Prevents the rapid spread of fire; which could trap the occupants of a building
- Reduces the chance of fires growing and creating danger to occupants, fire and rescue services, and people within the vicinity of the building
- Limits the damage caused to a building and its contents
Building Regulations Technical Guidance Document B (TGD-B) – Fire Safety defines a compartment (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 (a roof space above the top storey of a compartment is included in that compartment)”.
A compartment wall/floor is defined as:
“A fire-resisting wall/floor 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:
- The use of the building
- The fire load of the building
- The height of the building
- The availability of a sprinkler system
The maximum permissible dimensions of fire compartments are set out in Table 3.1 of Technical Guidance Document B (TGD-B) – Fire Safety.
The following is a brief synopsis of the requirements outline in Technical Guidance Document B (TGD-B) – Fire Safety.
Compartment walls and floor
- A wall common to two or more buildings should be constructed as a compartment wall
- Should be used to separate parts of a building used for different purposes or different tenancies
- Should be used to separate areas of special fire risk from other parts of a building
- Must for a complete barrier between the compartments they separate
- Have the appropriate fire resistance depending on the building construction
- Be constructed in accordance with the relevant Irish/European guidelines
- Compartment walls that are common to two or more building 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
- The lowest floor in a building is not required to be a compartment floor
- In a building which is 10 metres or more high any compartment floor is required to have a fire resistance of 60 minutes or more should be constructed of non-combustible material
- If a building which have existing timber floors it is possible to increase the fire resistance of the floor by:
- Addition of fire resistant layers beneath the existing floor covering
- 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:
- A door which is needed to provide means of escape in case of fire and which has the same fire resistance as that required for the wall (see Appendix B, Table B1 – TGD-B) and fitted in accordance with the provisions of Appendix B – TGD-B; and
- The passage of pipes that meet the provisions of Section 3.4 of TGD-B.
Openings in compartment walls (other than separating walls) or compartment floors should be limited to those for:
- Doors which have the appropriate fire resistance given in Appendix B, Table B1, and are fitted in accordance with the provisions of Appendix B – TGD-B; and
- The passage of pipes, ventilation ducts, chimneys, appliance ventilation ducts or ducts encasing one or more flue pipes, which meet the provisions in sub-section 3.4 of TGD-B; and
- Refuse chutes of non combustible construction
- Protected shafts which meet the relevant provisions
- 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”.
The function of a fire door is to protect escape routes and the contents and structure of building. They do so by limiting the spread of smoke and fire.
When a fire door is specified it means the complete door assembly, i.e.
- Door leaf or leaves
- Door frame
- Intumescent strips
- Smoke seals
The complete fire door assembly is required to conform with Irish/European Standards.
Fire doors are rated as meeting the recommendations of performance for integrity. The Integrity of the fire door assembly means it ability to resist penetration by flames and hot gases. The rating relates to the requirements per time which the integrity is held i.e. a door with E30 or FD30 satisfies requirements for 30 minutes and normally has intumescent strips fitted. Where the door assemblies are additionally prescribed as having an “S” rating (i.e. 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.
Appendix B of TGD-B provides for information and requirements for fire doors.
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:
- Resistance to collapse, i.e. the ability to maintain load-bearing capacity (applies to load-bearing members)
- Resistance to fire penetration, i.e. an ability to maintain the integrity of the element (applies to fire separating elements)
- Resistance to the transfer of excessive heat, i.e. an ability to provide insulation from high temperatures (applies to fire-separating elements)
The measure of its ability is usually express in terms of time. The measure of time is usually given as 30 minutes fire resistance, 60 minutes fire resistance etc.
Factors that have a bearing on fire resistance are:
- Fire severity
- Building height, or depth
- Building occupancy, and
- Intervention by fire fighters
Periods of fire resistance
Periods of fire resistance are subject to building regulations approval as granted through the fire safety certificate application process administrated by the local authority building control. Minimum periods of fire resistance are outlined in Appendix A and B of Technical Guidance Document B (TGD-B). The building control authority may impose a higher standard of fire resistance rating than those recommended in TGD-B.
There are also other interested parties who have legislative control over certain premises and therefore may need to be consulted, depending on the use of the premises, before any works are undertaken. These are likely to include:
- Health Service Executive
- Environmental Health Department (local authority)
- Petroleum licensing officer (Dublin Fire Brigade)
- Insurers of property
- Licensing of premises i.e. intoxicating liquor licence, public dance licence, gaming and lottery licence etc. (Dublin Fire Brigade)
- Conservation department (local authority)
Applying fire resistance
An ‘element of structure’ is a construction that normally performs an important function within a building e.g. a load bearing wall, ceiling, separating wall, floor etc.
When a requirement or recommendation is made for an existing ‘element of structure’ to be made fire resisting, the materials should be applied to the ’risk’ side, e.g., if it is recommended or required that a kitchen be separated from the adjoining accommodation, the fire resisting materials should be applied on the kitchen side of the wall. Likewise, if a cupboard under the stairs is to be made fire resisting, the interior of the cupboard should be lined with fire resisting materials.
Where pipe-work or other services pass through a fire resisting structure, it is essential to ensure that all gaps are sealed with fire resisting material such as plaster, to prevent the passage of fire, smoke and other products of combustion to adjoining rooms or premises. Proprietary methods of sealing pipe openings to maintain adequate fire resistance are available, such as pipe collars and intumescent sealants.
Walls and doors
Walls that are required to be fire resisting must extend from true floor to true ceiling and be imperforate. Suitable materials for this would be brick, block work or stud work partitioning with a 12.5mm thickness of cement plaster, or 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.
- 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, normally on all four sides. Fire door manufacturer’s guidance on maximum gaps should 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.
Floors and ceilings
Floors and ceilings can be made fire resisting by applying fire resisting materials to either the underside of the ceiling or to the floor above. Materials applied to the ceiling can be a minimum of 12.5mm plasterboard with joints taped, filled and covered with a plaster finish, or a minimum of 9.5mm plasterboard with at least 10mm lightweight gypsum plaster finish.
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 or 22mm plaster on striated (rough) wood or reed lath, and to 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. It should be 3.2mm standard hardboard Type S to IS EN 13501: Part 1 (or 4mm plywood) nailed at not more than 150mm centres on the line of joints. The joints are to coincide with the line of joists. Alternatively a suitable Fire Resisting material may be positioned below the floor boards instead of the hardboard above.
There is glass available that meets the required standards of fire resistance. This 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; consideration must be given to the construction as a whole to determine this. Manufacturers of glass and glazed screens can supply details on whether a particular construction i.e. screen or doorset can meet the necessary standard.
Fire resisting glass is categorised as 'insulating' or 'non-insulating'. Technical Guidance Document B – TGD-B – Table A4 limits the use of ‘non-insulating’ glazing in certain location.
The above methods are given as examples of effective ways of achieving a level of fire resistance. There are many other ways of achieving a similar standard of fire resistance, for more information, visit the sites below.
Department of Housing, Planning and Local Government:
- Technical Guidance Document B – Fire Safety (2006)
- Fire safety Management in Places of Assembly
- Fire Safety in Flats
- Fire Safety in Gaeltacht
- Fire Safety in Pre-Schools
- 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.
Timber Research and Development Association:
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