Compartmentation and appropriate fire stopping are still the main ways of stopping fires spreading and so limiting death and injury. Andy Kay reviews the measures that should be taken.
There is a worrying statistic that 44% of fire related deaths happen to people who were outside the room of origin of the blaze; worrying because these deaths are preventable. In April 1996, a fire broke out in Dusseldorf airport. A welder had set fire to some polystyrene insulation and the resultant blaze led to 17 deaths. Eight people were killed in a VIP lounge, several hundred metres from the seat of the fire. Smoke and noxious gasses had spread uncontrollably though the ventilation ducts and caught the occupants of the lounge unawares. Had the compartmentation within the building been adequate, these deaths may not have occurred.
Another tragic case in January 2004 led to the deaths of 14 residents in the Rosepark care home in Glasgow. The fire remained in a fairly contained area, but the build up of pressure led to thick smoke being forced though every part of the home and the elderly patients all died of smoke inhalation. Chief superintendent Tom Buchan said at the time: “It was not what you would call a significant fire, in the sense that the premises were destroyed. There is, in fact, very little damage.”
There are five main strands to an effective fire strategy within a building:
– Prevention – this speaks for itself. Prevent fires from breaking out and everyone is happy. However, the reality is that fires are inevitable and with arson on the increase, the best housekeeping and preventative measures have only a minimal effect on fire statistics.
– Detection – this is provided by smoke and fire alarms.
– Suppression – suppression systems include mechanically activated systems (referred to as active) such as sprinklers and gas suppression systems, as well as fire extinguishers and blankets.
– Evacuation – the Building Regulations are designed to save lives and ensure the safe evacuation of a building.
– Containment – keeping the fire, smoke and noxious gasses to a restricted area and achieved by dividing a building up into fire rated compartments. This not only aids evacuation and thus saves lives, but it is also the primary strategy for property protection. Annual insured losses from fires in Great Britain break the GB pound 1 billion mark, but combined with uninsured losses the true figure is somewhere between GB pound 6 billion and GB pound 7 billion.
Compartments
When a building is designed, there are regulations governing the size of compartments within the building in order to reduce the risk of fire spread. The walls, floors and ceilings of these compartments will have a fire and insulation rating, generally ranging from 1/2 hour to a maximum of four hours – depending on the usage of the premises, the sighting of the compartment or the presence of sprinkler systems. The idea is that in the event of fire the flame, heat and smoke produced will stay within the compartment, thus reducing the risk to both lives and property. This process is called compartmentation.
The construction of the walls, floors and ceilings will be carried out in accordance with these design criteria, but in order for any compartment to be usable by its occupants, breaches have to be made for such elements as doors, mechanical and electrical services and expansion joints. It’s these breaches that need to be addressed through the installation of built-in (passive) fire measures. The most commonly recognised built-in fire protection is the fire door and most of us now know that propping them open, usually with a handily placed fire extinguisher, is not best practice! However, a compartment wall has to run from floor slab to ceiling soffit. The fire door may well be sat on top of a computer deck/raised access floor with a suspended ceiling above. Take a moment to push up some ceiling tiles above a fire door and you will often be faced with multiple services passing though the wall. If these services have not been adequately protected, then the money spent on the fire door has been wasted. Fire is not discriminatory: it will find the least line of resistance to pass from one compartment to another.
The types of products used to protect these services are generally referred to as fire-stopping. There are whole sections of Approved Document B of the England and Wales Building Regulations devoted to compartmentation. Similar guidance is given in the Scottish Technical Manuals, Part E of the Northern Ireland Regulations and Technical Guidance Document B in Eire. The most pertinent sections that apply to fire-stopping are:
10.2: REINSTATEMENT OF COMPARTMENTS: “If a fire separating element is to be effective, then every joint, or imperfection of fit, or opening to allow services to pass through the element, should be adequately protected by sealing or fire-stopping so that the fire resistance of the element is not impaired”
10.17: FIRE-STOPPING: “In addition to any other provisions in this document for fire-stopping:
a. joints between fire separating elements should be fire-stopped; and
b. all openings for pipes, ducts, conduits or cables to pass through any part of a fire-separating element should be:
i. kept as few in number as possible, and
ii. kept as small as practicable, and
iii. fire-stopped (which in the case of a pipe or duct, should allow for thermal movement).”
8.27: HEAD OF WALL: Compartment walls should be able to accommodate the predicted deflection of the floor above by:
having a suitable head detail between the wall and the floor, that can deform but maintain integrity when exposed to fire.
There are many proprietory fire-stop products available that are designed to seal around compartment breaches and fill construction joints, thereby reinstating the integrity of the wall, floor or ceiling to its original design criteria. Active and passive systems are not mutually exclusive, but should be used together to provide a holistic fire strategy for a building.
Passive products need to not only provide a flame, heat and smoke barrier, but also need to accommodate the possibility of services burning away and leaving holes in the compartment. A good example is a sanitary soil pipe passing through a wall. These are generally 110mm plastic pipes. Just sealing around these pipes will be inadequate because the fire will cause the pipe to melt and burn away very quickly, leaving a large hole for the fire and smoke to pass through. One solution to this is a pipe collar that is wrapped around the pipe and fixed to the wall. Inside the pipe collar is a material that, when exposed to heat will expand and exert pressure on the plastic as it softens, eventually crushing the pipe before the flame and smoke can pass through the wall. These types of expanding materials are called intumescent products. The most common active ingredient is graphite, which is the fastest reacting intumescent currently available.
The term ‘fire-stop’ intimates that the products are designed to stop the spread of fire. Although this is true, it is also important to remember that they serve other functions as well. If you want to block an opening to stop a flame going though, the easiest way would be to bolt a steel plate over the hole. However, although this would stop the flame, the heat build up could lead to materials combusting on the non-fire side of the wall or floor and the fire would spread outside of the compartment. Therefore, the Building Regulations call for products to be tested for their thermal insulation properties as well i.e. their ability to withstand the passage of heat. In all cases, the thermal requirement will be equivalent to fire rating. If a product has achieved 90 minutes’ fire resistance but only 60 minutes’ thermal resistance, it should only be used where there is a 60 minute requirement.
In many applications, the firestop products have to accommodate movement of the services or joints in everyday usage. Sealants used around hot water pipes, or chiller pipes, can be subject to expansion, or contraction of the pipework that will produce both tensile and shear loads on the product. If the product is incapable of meeting this criteria it is likely that it will fail when exposed to fire. The gap between the slab edge and a curtain wall construction will be subject to continuous movement of the curtain wall facade, due to positive and negative wind loads and therefore, the firestopping product used in this application should be able to demonstrate its ability to recover its shape through cyclic testing.
One contentious area in the Building Regulations is whether it is necessary to fire-stop plastic penetrations with a diameter of 40mm or less. There are ambiguities in the wording that have led many to believe that this is not necessary. The interpretation supported by ASFP is that below 40mm it is not necessary to use proprietary systems, but other forms of basic firestop must be used. Plastic pipes of this diameter will burn through, usually in under five minutes, and two 40mm pipes in a fire compartment wall are capable of letting through over 2000 litres of smoke and noxious gasses in just five minutes – enough to fill 1000 lungs.
Smoke is the biggest killer in a fire. 75% of fire deaths are through smoke inhalation and so it is critical that when applying fire-stop products a cold smoke seal is achieved. In a fire, the pressure within a compartment will build significantly. Most service penetrations are at a high level through a wall or through the soffit. These are the areas of highest pressure and under such pressure smoke and noxious gasses will be forced through the smallest gaps or imperfections of fit. Smoke expands rapidly to fill any sized void and can travel at up to 10m per second.
We can clearly see from the Dusseldorf Airport tragedy that fire and smoke protection measures are necessary within air conditioning and ventilation systems. These are provided by the installations of dampers. Fire dampers are fitted where ductwork passes through fire compartment walls, or floors, as part of a fire control strategy. In normal circumstances, these dampers are held open by means of fusible links. When subjected to heat, these links fracture and allow the damper to close under the influence of the integral closing spring. The links are attached to the damper such that the dampers can be released manually for testing purposes. Dampers will be fail-safe by means of an electrical thermal release, which operates at 72 degrees C or by loss of power, complying with BS 5588.
So who carries the can if the compartmentation measures are proved to be inadequate after a fire has occurred? If we look at the two examples of Dusseldorf and Rosepark, we can see that it is invariably the building owners that are first in the firing line. The fact is that everyone involved in the design, construction, product supply and running of a building could end up in court ,should the unthinkable occur. Compartmentation is a simple strategy that can have a major effect on improving life safety and reducing property losses. It could also keep you out of court!
Andy Kay is chairman of the Association for Specialist Fire Protection (ASFP).
Compartmentation and appropriate fire stopping are still the main ways of stopping fires spreading and so limiting death and injury. Andy Kay reviews the measures that should be taken.
There is a worrying statistic that 44% of fire related deaths happen to people who were outside the room of origin of the blaze; worrying because these deaths are preventable. In April 1996, a fire broke out in Dusseldorf airport. A welder had set fire to some polystyrene insulation and the resultant blaze led to 17 deaths. Eight people were killed in a VIP lounge, several hundred metres from the seat of the fire. Smoke and noxious gasses had spread uncontrollably though the ventilation ducts and caught the occupants of the lounge unawares. Had the compartmentation within the building been adequate, these deaths may not have occurred.
Another tragic case in January 2004 led to the deaths of 14 residents in the Rosepark care home in Glasgow. The fire remained in a fairly contained area, but the build up of pressure led to thick smoke being forced though every part of the home and the elderly patients all died of smoke inhalation. Chief superintendent Tom Buchan said at the time: "It was not what you would call a significant fire, in the sense that the premises were destroyed. There is, in fact, very little damage."
There are five main strands to an effective fire strategy within a building:
• Prevention – this speaks for itself. Prevent fires from breaking out and everyone is happy. However, the reality is that fires are inevitable and with arson on the increase, the best housekeeping and preventative measures have only a minimal effect on fire statistics.
• Detection – this is provided by smoke and fire alarms.
• Suppression – suppression systems include mechanically activated systems (referred to as active) such as sprinklers and gas suppression systems, as well as fire extinguishers and blankets.
• Evacuation – the Building Regulations are designed to save lives and ensure the safe evacuation of a building.
• Containment – keeping the fire, smoke and noxious gasses to a restricted area and achieved by dividing a building up into fire rated compartments. This not only aids evacuation and thus saves lives, but it is also the primary strategy for property protection. Annual insured losses from fires in Great Britain break the £1 billion mark, but combined with uninsured losses the true figure is somewhere between £6 billion and £7 billion.
Compartments
When a building is designed, there are regulations governing the size of compartments within the building in order to reduce the risk of fire spread. The walls, floors and ceilings of these compartments will have a fire and insulation rating, generally ranging from 1/2 hour to a maximum of four hours – depending on the usage of the premises, the sighting of the compartment or the presence of sprinkler systems. The idea is that in the event of fire the flame, heat and smoke produced will stay within the compartment, thus reducing the risk to both lives and property. This process is called compartmentation.
The construction of the walls, floors and ceilings will be carried out in accordance with these design criteria, but in order for any compartment to be usable by its occupants, breaches have to be made for such elements as doors, mechanical and electrical services and expansion joints. It’s these breaches that need to be addressed through the installation of built-in (passive) fire measures. The most commonly recognised built-in fire protection is the fire door and most of us now know that propping them open, usually with a handily placed fire extinguisher, is not best practice! However, a compartment wall has to run from floor slab to ceiling soffit. The fire door may well be sat on top of a computer deck/raised access floor with a suspended ceiling above. Take a moment to push up some ceiling tiles above a fire door and you will often be faced with multiple services passing though the wall. If these services have not been adequately protected, then the money spent on the fire door has been wasted. Fire is not discriminatory: it will find the least line of resistance to pass from one compartment to another.
The types of products used to protect these services are generally referred to as fire-stopping. There are whole sections of Approved Document B of the England and Wales Building Regulations devoted to compartmentation. Similar guidance is given in the Scottish Technical Manuals, Part E of the Northern Ireland Regulations and Technical Guidance Document B in Eire. The most pertinent sections that apply to fire-stopping are:
10.2: REINSTATEMENT OF COMPARTMENTS: "If a fire separating element is to be effective, then every joint, or imperfection of fit, or opening to allow services to pass through the element, should be adequately protected by sealing or fire-stopping so that the fire resistance of the element is not impaired"
10.17: FIRE-STOPPING: "In addition to any other provisions in this document for fire-stopping:
a. joints between fire separating elements should be fire-stopped; and
b. all openings for pipes, ducts, conduits or cables to pass through any part of a fire-separating element should be:
i. kept as few in number as possible, and
ii. kept as small as practicable, and
iii. fire-stopped (which in the case of a pipe or duct, should allow for thermal movement)."
8.27: HEAD OF WALL: Compartment walls should be able to accommodate the predicted deflection of the floor above by:
having a suitable head detail between the wall and the floor, that can deform but maintain integrity when exposed to fire.
There are many proprietory fire-stop products available that are designed to seal around compartment breaches and fill construction joints, thereby reinstating the integrity of the wall, floor or ceiling to its original design criteria. Active and passive systems are not mutually exclusive, but should be used together to provide a holistic fire strategy for a building.
Passive products need to not only provide a flame, heat and smoke barrier, but also need to accommodate the possibility of services burning away and leaving holes in the compartment. A good example is a sanitary soil pipe passing through a wall. These are generally 110mm plastic pipes. Just sealing around these pipes will be inadequate because the fire will cause the pipe to melt and burn away very quickly, leaving a large hole for the fire and smoke to pass through. One solution to this is a pipe collar that is wrapped around the pipe and fixed to the wall. Inside the pipe collar is a material that, when exposed to heat will expand and exert pressure on the plastic as it softens, eventually crushing the pipe before the flame and smoke can pass through the wall. These types of expanding materials are called intumescent products. The most common active ingredient is graphite, which is the fastest reacting intumescent currently available.
The term ‘fire-stop’ intimates that the products are designed to stop the spread of fire. Although this is true, it is also important to remember that they serve other functions as well. If you want to block an opening to stop a flame going though, the easiest way would be to bolt a steel plate over the hole. However, although this would stop the flame, the heat build up could lead to materials combusting on the non-fire side of the wall or floor and the fire would spread outside of the compartment. Therefore, the Building Regulations call for products to be tested for their thermal insulation properties as well i.e. their ability to withstand the passage of heat. In all cases, the thermal requirement will be equivalent to fire rating. If a product has achieved 90 minutes’ fire resistance but only 60 minutes’ thermal resistance, it should only be used where there is a 60 minute requirement.
In many applications, the firestop products have to accommodate movement of the services or joints in everyday usage. Sealants used around hot water pipes, or chiller pipes, can be subject to expansion, or contraction of the pipework that will produce both tensile and shear loads on the product. If the product is incapable of meeting this criteria it is likely that it will fail when exposed to fire. The gap between the slab edge and a curtain wall construction will be subject to continuous movement of the curtain wall facade, due to positive and negative wind loads and therefore, the firestopping product used in this application should be able to demonstrate its ability to recover its shape through cyclic testing.
One contentious area in the Building Regulations is whether it is necessary to fire-stop plastic penetrations with a diameter of 40mm or less. There are ambiguities in the wording that have led many to believe that this is not necessary. The interpretation supported by ASFP is that below 40mm it is not necessary to use proprietary systems, but other forms of basic firestop must be used. Plastic pipes of this diameter will burn through, usually in under five minutes, and two 40mm pipes in a fire compartment wall are capable of letting through over 2000 litres of smoke and noxious gasses in just five minutes – enough to fill 1000 lungs.
Smoke is the biggest killer in a fire. 75% of fire deaths are through smoke inhalation and so it is critical that when applying fire-stop products a cold smoke seal is achieved. In a fire, the pressure within a compartment will build significantly. Most service penetrations are at a high level through a wall or through the soffit. These are the areas of highest pressure and under such pressure smoke and noxious gasses will be forced through the smallest gaps or imperfections of fit. Smoke expands rapidly to fill any sized void and can travel at up to 10m per second.
We can clearly see from the Dusseldorf Airport tragedy that fire and smoke protection measures are necessary within air conditioning and ventilation systems. These are provided by the installations of dampers. Fire dampers are fitted where ductwork passes through fire compartment walls, or floors, as part of a fire control strategy. In normal circumstances, these dampers are held open by means of fusible links. When subjected to heat, these links fracture and allow the damper to close under the influence of the integral closing spring. The links are attached to the damper such that the dampers can be released manually for testing purposes. Dampers will be fail-safe by means of an electrical thermal release, which operates at 72°C or by loss of power, complying with BS 5588.
So who carries the can if the compartmentation measures are proved to be inadequate after a fire has occurred? If we look at the two examples of Dusseldorf and Rosepark, we can see that it is invariably the building owners that are first in the firing line. The fact is that everyone involved in the design, construction, product supply and running of a building could end up in court ,should the unthinkable occur. Compartmentation is a simple strategy that can have a major effect on improving life safety and reducing property losses. It could also keep you out of court!
Andy Kay is chairman of the Association for Specialist Fire Protection (ASFP).
