70% of fire victims suffocate.
If you think that five breaths are all it takes to lose consciousness, you won’t be surprised to learn that between 50-80% of victims in a fire suffocate. Thick smoke can lead to disorientation and make it difficult to breathe, while the heat can cause parts of the building to collapse and start secondary fires. All this makes it difficult for people to find their way out of the building and for emergency services to make their way in to fight the fire.
Stopping the movement of smoke and heat
Over time, people have recognised the need for effective escape routes as well as fire and smoke compartments in order to prevent the movement of smoke and heat. However, the architectural trend is for buildings with large open spaces, hence no compartmentation. Fire and smoke curtains can provide a solution. They can be perfectly integrated into the building’s design so that they are virtually invisible when rolled up. They can also be connected to fire detection systems that will trigger them so that, in the case of a fire, they roll down creating compartments to prevent the movement of fire, heat and smoke.
Compartments help smoke ventilation
Creating compartments also helps ventilators extract the smoke efficiently. Hot smoke is more buoyant and tends to go up, so that natural ventilators will find it easier to extract it quickly. If the smoke is allowed to cool by moving around the building, it will tend to return to ground level.
Smoke dampers are passive fire protection products used in air conditioning and ventilation ductwork or installed in physical smoke barriers (e.g., walls), and form an integral and essential part of the building's passive fire protection system, and is usually done to prevent the spread of smoke from the space of fire ignition to other spaces in the same building. A combination of fans and dampers can exhaust smoke from an area while pressurising the smoke-free areas around the affected area (inhibiting smoke infiltration into additional areas).
While forming an essential part of the fire protection system, a poorly maintained fire / smoke damper can prove lethal in the event of a fire, and can actually act as an accelerant during a flashover.
Flashovers happen when the fire involving the initial item, for instance a sofa, can produce a layer of hot smoke which spreads across the ceiling in the room. The hot buoyant smoke layer grows in depth, as it is contained by the walls of the room. The radiated heat from this smoke layer heats the surfaces of the directly exposed combustible materials in the room, causing them to give off flammable gases. When the temperatures of the evolved gases become high enough, these gases will ignite. This causes a mini explosion, known as a flashover.
If smoke dampers are not correctly maintained, then during flashover they can act as a chimney, and draw the burning gases through to other parts of the building extremely rapidly.
The bottom line? Ensure that your dampers are correctly and regularly maintained by competent passive fire safety technicians.
About me: I am one of the project managers at Ventro Group, a Passive Fire consultancy firm specialising in the auditing, maintenance and installation of all passive fire safety systems and equipment including fire compartmentation, fire doors, fire stopping and fire dampers. My particular focus is on HMOs (House in Multiple Occupation) both in the private and public sector. Views are my own, but generally I write about my thoughts on fire safety.