When people think of fire protection in their building, they usually think of active fire protection systems. These are the ones you can see or operate like sprinklers, fire extinguishers and alarms. Occupiers are often unaware of the passive protection measures that have been interwoven into the design and structure of the building. These systems are called passive because they do not require any actions or interventions to work.
Passive fire protection is part of the building’s fire safety strategy which works to contain or slow the spread of fire and smoke. Measures are implemented to allow occupants to safely evacuate, to protect neighbouring properties and facilitate the activities of emergency services. We will discuss some examples of passive fire protection in this article.
The foremost way to minimise the spread of fire and smoke and maintain structural stability in a building is using fire-resisting construction.
The National Construction Code (NCC) sets out requirements for fire-resisting construction based on the type of construction and class of a building. When designing a building of Type A construction, the external and common walls must be non-combustible. Non-combustible materials include steel, concrete, natural stone, aluminium and plasterboard.
A building element might be required to be non-combustible and/or have a certain Fire-resistance level (FRL). FRL is a term used to describe the fire resistance of building elements as determined in the standard test for fire resistance. That is how long it can control or reduce the spread of fire, gas and heat and retain its own or loadbearing structural strength. These elements include fire rated walls, beams, columns, roofs, floors and doors. For example, an external wall can be required to have an FRL of at least 60/60/60 when tested from the outside.
But there is no point having a fire resisting wall and then putting a regular door in it and so fire doors are installed as a fire barrier. Also known as fire resistant doorsets, the door frame and door leaf are tested as a set and have a FRL. Any hardware added to the fire resistant doorset (handles, locks, self-closers) must be tested and approved for the use in conjunction with fire doors. Fire doors are required to be self-closing and latching and must be kept closed at all times or close in the event of a fire.
Separation and compartmentalisation are effective ways of controlling and containing a potential fire. Compartmentalisation involves dividing an area or building into separate compartments to prevent the spread of fire and smoke. Fire walls, fire ceilings and fire stopping are examples of measures which help contain fires within specific areas.
Fire separation is managed by the use of fire-rated walls, doors and floors that act as a barrier against the spread of fire within the building and to adjoining properties.
The NCC specifies fire separation in some instances. For example, when there are two classes in one storey of a building, steps must be taken to minimise the risk of a fire in one causing the failure of building elements in the another. This is done by either selecting the highest of the two FRLs required for each building to construct a fire-resisting barrier or placing a fire wall between the two classifications.
Fire and smoke can quickly spread through building ventilation systems and openings made for ductwork. To stop this, fire dampers and smoke dampers are installed where ducts from heating, ventilation or air conditioning systems pass through walls, ceilings or floors.
While it is easy to overlook these passive components as they require little routine maintenance, it is still imperative that they are maintained to the original standard of performance. It is also important that they are not tampered with or used incorrectly. Wedging a fire door open or drilling a hole for a new light in your fire-resisting ceiling could have a detrimental effect.
Related online courses:
Fire Resistance & Fire Hazard Properties