Passive fire protection is a term that encompasses a broad spectrum of products and practices. In the most simplistic sense, passive fire protection refers to materials built into the structures that surround us which are intended to slow or prevent the spread of fire.
The purpose of PFP is to maximise the time available to evacuate a property, or prevent a fire from taking hold in the first place.
The concept of passively protecting against fire has applications outside of the building industry though. The term is most often associated with intumescent or fireproof building materials, but also applies to products such as fire retardant sprays which are designed to increase the base fire resistance of fabrics and decorative items. The common factor is that regardless of the application, passive fire protection is universally intended to delay or prohibit the spread of fire whether from item to item, or room to room.
The following distinction may help further define the term. Active fire protection is a term that can be used to describe any systems or products put in place to detect or combat a fire (smoke detection, extinguishers etc). These systems will always need some form of trigger to activate, such as the smoke from a fire setting off detectors, or an extinguisher being discharged by a user.
Passive fire protection requires no activation. For example, a fire door is an effective fire resistant barrier without any need for external stimuli. The same can be said for fire rated glass and plasterboard. Both of these materials are designed to be inherently fire resistant until the point when they eventually give way to the fire, or the fire is extinguished.
An exception to this rule which should be noted is intumescent material. This type of PFP reacts by expanding when exposed to heat in order to seal penetrations (pipes, cabling etc.) through otherwise fire resistant surfaces. Once the intumescent material has fully activated, crushing a pipe or filling a void, the expanded product re-instates the fire barrier and stops flames or smoke from passing through.
Compartmentalisation is a frequently used term within the fire industry and is one of the core principles of Passive Fire Protection (PFP). An example of compartmentalisation would be the installation of (minimum) 30 minute fire rated barriers separating each distinct area throughout a property. The creation of layered pockets of fire resistance ensures a fire can be contained within a relatively small area, and therefore enables people to exit the building safely and minimises any damage to the property.
A common sign of compartmentalisation is a fire door. Fire doors should be rated to a minimum of 30 minutes fire resistance and are designed to completely seal off a doorway to prevent flames and smoke from passing through. Of course, fire doors must be accompanied by fire resistant walls and ceilings in order to prevent the spread of fire.
Care must therefore be taken to protect any penetrations made in walls, floors or ceilings as these can become conduits through which fire can spread. Intumescent products are designed to surround holes made in any fire resistant surfaces, and seal them in the event of a fire, maintaining compartmentalisation.
The provision of compartmentalisation is required by building regulations for both domestic and non-domestic properties.
Whilst it is vital to slow the passage of smoke and flames throughout any type of building, it is especially important in buildings providing care to anyone with limited mobility. In these types of premises, it is common to see a series of points marked as areas of refuge. These areas are designed to protect anyone unable to be safely evacuated in the early stages of a fire. These areas of refuge serve as a fine example of the importance of compartmentalisation, as they would not be possible without the consideration and application of passive fire protection during construction.
Basic fire safety requirements are a vital part of general building regulations. Any construction project that requires approval under building regulations must pass inspection by the local authority's building control department. An alternative is to engage the services of a private approved inspector, but any reports issued by third parties such as this must still be passed by the local authority.
All building work, whether an extension, structural alteration or a new build property must be constructed in accordance with The Building Regulations 2010, Fire Safety, Approved Document B.
Approved document B (known as Part B) of the building regulations was divided into two separate volumes as part of the 2006 revision of the document. Following this revision, which was applied from April 2007 onwards, volume 1 specifically covers properties defined as 'Dwellinghouses', with volume 2 covering 'Buildings Other Than Dwellinghouses'.
This split allowed for the expansion of guidance on topics specific to non-domestic properties, though it is interesting to note that, in respect of the structural aspect of fire safety, many of the regulations in volumes 1 and 2 are very similar. This is because passive fire protection measures are implemented with the common purpose of containing or retarding the spread of fire, regardless of the use or function of a building.
Following on from the changes made in 2006, there have been a number of updates since and the most recent version of this document is now the 2019 edition. Volume 1 was renamed and now refers to 'Dwellings' whilst Volume 2 continues to reference 'Buildings Other Than Dwellings'.
Both volumes of part B of the building regulations dictate in detail the minimum levels of fire resistance required, and emphasise the importance of robust compartmentalisation in building design and construction. They also give guidance relating to a range of specific circumstances, and the appropriate passive fire protection measures required.
Passive fire protection is directly referenced in the following subsections of both volumes of approved document B:
There are also numerous references to PFP concepts such as protected areas throughout the parts of the regulations referring to escape routes. This shows how integral passive fire protection is to almost all aspects of construction, and underlines the importance of the concept. Further details and information about intumescent materials.