Passive and Active Protection

Passive Fire Protection

Passive fire protection is a term used to describe the parts of a building or structure that provides a barrier to fire, containing and slowing the rate at which it spreads.  This is achieved by creating fire-resistant walls, floors and doors.  Passive fire protection also protects load bearing columns and other critical structures to prevent the building collapsing during fires. 

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By creating a fire resistant compartment between rooms and floors, passive fire protection greatly slows the spread of the fire from the room where it originated.  As a result the amount of damage that the building sustains is dramatically reduced.  In addition, the building’s occupants have more time to evacuate the building and reach a place of safety. 

The reason that passive fire protection is given its name is that it does not typically require any motion or to be activated by electronics.  There are some exceptions to this rule, such as fire door closers and fire dampers.

Listed below are some of the common problems with passive protection:

Fire Doors

  • Fire doors wedged or propped open
  • Smoke seals around doors missing, damaged or incorrectly fitted
  • Doors not closing or self latching (the door must close properly and stay shut)
  • Poorly fitted door in frame (gaps around the door)
  • Damaged fire doors
  • Self-closers must operate correctly
  • Cracked glazing

Walls and Ceilings

  • Breaches in fire compartment walls, floors and ceilings created by the installation of new services, e.g. computer cabling and pipes
  • Standard DIY expanding foam used to fill holes in walls (not fire resistant)
  • The fire resistance above false ceilings do not extend up to the floor above
  • Cavities and voids allowing the potential for a fire to spread unseen

Unlike passive fire protection, active fire protection systems interact with their surroundings e.g. by operating fans for smoke extraction, operating a fire sprinkler to control or extinguish a fire, or opening a vent to allow assisted natural ventilation.

The first stage of active fire protection is to detect the fire, by detecting heat, smoke or flames (an automatic fire alarm system is commonly used to trigger most active systems), this then automatically operates the active systems (extraction fans etc).

Active systems are particularly useful in larger buildings where it is difficult to ventilate central areas through natural openings such as windows, smoke and heat extraction systems are often used.  Their purpose is improve the visibility in the building so that occupants can make their exit and to prevent flashover. 

Sprinkler systems, typically installed at ceiling height, will also be activated.  This usually occurs when excessive heat from the fire causes glass in the system to burst, thus releasing the water.  Sprinklers only release the water in the location of the fire, preventing damage to other areas of the building. 

Using active fire protection systems has some benefits such as permitting design freedoms and encourage innovative, inclusive and sustainable architecture.

For more information refer to our page on fire sprinklers.