Fire can spread through a building via m&e services routes unless they are properly firestopped. Andy Kay reviews state-of-the-art techniques
There is a worrying statistic that 44% of fire-related deaths involve people who were outside the room of origin of the blaze – worrying because these deaths were preventable.
In April 1996 a fire broke out in Düsseldorf 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 gases 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 would not have occurred.
In another tragic case in January 2004, a faulty fuse 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 a significant fire in the sense that the premises were destroyed. There is in fact very little damage.”
These deaths were preventable.
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 half an hour to a maximum of four hours, depending on use of premises, siting of the compartment and whether sprinkler systems are installed.
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, breaches have to be made for such elements as doors, mechanical and electrical services and expansion joints. Built-in (passive) fire measures need to be incorporated to ensure the breaches are still fireproofed.
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 or raised-access floor with a suspended ceiling above. If services have not been adequately protected, 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.
There are many proprietary firestop 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.
Firestopping products are generally referred to in the industry as ‘passive’ or ‘built-in’ fire protection, as distinct from sprinklers and similar protective equipment, which are ‘active’. Passive and active systems are not mutually exclusive but should be used together to provide a holistic fire strategy for a building.
Passive products need not only to provide a flame, heat and smoke barrier but also accommodate the possibility of services burning away and leaving holes in the compartment.
One solution to this is a pipe collar. This is wrapped round 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 ‘firestop’ suggests that the products are designed to stop the spread of fire. Although this is true, it is important to remember that they serve other functions.
If you want to block an opening to stop a flame going through, the easiest way would be to bolt a steel plate over the hole. But although this would stop the flame, the heat build-up could lead to materials catching fire on the side of the wall or floor away from the fire, and the fire would spread outside the compartment.
The Building Regulations also call for products to be tested for their thermal insulation properties, that is, their ability to withstand the passage of heat. In all cases, the thermal requirement will be equivalent to a 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 services or joints in everyday use. Expansion or contraction of pipework can create both tensile and shear loads on sealants used around hot-water or chiller pipes. If the product is incapable of meeting this criteria, it is likely that it will fail when exposed to fire.
One contentious area in the Building Regulations is whether it is necessary to firestop plastic penetrations with a diameter of 40 mm or less. There are ambiguities in the wording that have led many to believe this is not necessary. The interpretation supported by the Association of Specialist Fire Protection is that, below 40 mm, 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 40 mm penetrations in a fire compartment wall are capable of letting through more than 2000 litres of smoke and noxious gases in just five minutes. That’s enough to fill 1000 lungs.
Smoke is the biggest killer in a fire. Some 75% of fire deaths are through smoke inhalation, so it is critical that a cold smoke seal is achieved.
In a fire, the pressure in 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 gases 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 10 metres per second.
We can clearly see from the Düsseldorf Airport tragedy that fire and smoke protection measures are necessary in air-conditioning and ventilation systems. These are provided by 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 failsafe by means of an electrical thermal release that operates at 72°C or by loss of power, complying with BS 5588.
Who carries the can if compartmentation measures are proved to be inadequate after a fire? If we look at the Düsseldorf and Rosepark cases, we see that it is the building owners that are first in the firing line. In Düsseldorf, the airport authorities were sued by four insurance companies and were ordered to pay $11m in compensation. The court judged that the airport’s building contractors were negligent, and so in turn the airport sued the contractors. There were also criminal prosecutions brought against the airport owners by the families of the deceased.
In the Rosepark case, three members of the Balmer family, who were all partners of the firm that ran the home, were accused of 12 charges, including breaches of the Health and Safety at Work Act 1974, the Health and Safety at Work Regulations 1999 and the Electricity at Work Regulations 1989.
Compartmentation is a simple strategy that can have a major effect on improving life safety and reducing property losses during a fire – and it could help to keep you out of court.
Originally published as "Stay where you are" in EMC Jul/Aug 2009
Saving the UK £7bn a year by taking five golden steps
There are five main strands to an effective fire strategy within a building.
Prevention – Prevent fires from breaking out and everyone is happy. But 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 statistics.
Detection – Provided by smoke and fire alarms.
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 help save lives and ensure the safe evacuation of a building.
containment – Keeping the fire, smoke and noxious gases to a restricted area is achieved by dividing a building up into fire-rated compartments. This not only aids evacuation and saves lives, it is also the primary strategy for property protection. Insured losses from fires in the UK annually break the £1 billion mark, but combined with uninsured losses, the true figure is somewhere between
£6 billion and £7 billion.
Electrical and Mechanical Contractor
Andy Kay is national firestop manager at Hilti and chairman of the Association for Specialist Fire Protection