Existing layout and construction

Existing layout and construction

In many shops, and increasingly in offices, the design is for open-plan areas allowing customers and employees to move freely throughout the floor.

Traditionally, occupants are advised to shut doors when escaping from a fire but in open plan areas there are few doors to shut. In these areas the fire, and especially the smoke, may spread faster than expected.

To assess the risk in your premises you need to evaluate the construction and layout of your premises. This does not mean a structural survey, unless you suspect that the structure is damaged or any structural fire protection is missing or damaged, but rather an informed look around to see if there are any easy paths through which smoke and fire may spread and what you can do to stop that. In general, older buildings will have more void areas, possibly hidden from view, which will allow smoke and fire to spread away from its source.

Whatever your type of building, you may need to consider typical situations that may assist the spread of fire and smoke such as:

• vertical shafts, e.g. lifts, open stairways, dumb waiters or holes for moving stock around;
• false ceilings, especially if they are not fire-stopped above walls;
• voids behind wall panelling;
• unsealed holes in walls and ceilings where pipe work, cables or other services have been installed; and
• doors, particularly to stairways, which are ill-fitting or routinely left open.

Particular hazards in corridors and stairways used as escape routes

Items that are a source of fuel, pose an ignition risk, or are combustible and likely to increase the fire loading or spread of fire, should not be located on any corridor or, stairway or circulation space that will be used as an escape route.

Such items include:

• portable heaters, e.g. bottled gas (LPG) or electric radiant heaters and electric convectors or boilers;
• gas cylinders for supplying heaters;
• cooking appliances; and
• unenclosed gas pipes, meters, and other fittings.

However, where more than one escape route is available and depending on the findings of your risk assessment, items such as those below may be acceptable if the minimum exit widths are maintained and the item presents a relatively low fire risk:

• non-combustible lockers;
• vending machines;
• small items of electrical equipment (e.g. photocopiers); and
• small coat racks and/or small quantities of upholstered furniture which meets BS 7176 or the Furniture andFurnishings (Fire) (Safety) Regulations 1988.

Insulated core panels

Many buildings have insulated core panels as exterior cladding or for internal structures and partitions. The food industry, in particular, uses insulated core panels because they are easy to clean and facilitate consistent temperature control within the premises. The simple construction of these panels’ enables alterations and for additional internal partitions to be erected with minimum disruption to business.

They normally consist of a central insulated core, sandwiched between an inner and outer metal skin. There is no air gap. The external surface is then normally coated with a PVC covering to improve weather resistance or the aesthetic appeal of the panel. The central core can be made of various insulating materials, ranging from virtually non-combustible through to highly combustible. Differing fire hazards are associated with common types of insulation, when the panels are subjected to certain temperatures. Typical examples are:

• Mineral rock/modified phenolic will produce surface char and little smoke or gaseous combustion products, at temperatures above 230°C.
• Polyisocyanurate (PIR)/polyurethane (PUR) will char and will generate smoke and gaseous combustion products, at temperatures above 430°C PIR and 300°C PUR.
• Expanded polystyrene (EPS) will melt and will generate smoke and gaseous combustion products, at temperatures above 430°C PIR.

Insulation charring can lead to panel delamination/collapse, and the gaseous combustion products can fill areas with the toxic gases carbon monoxide and styrene.

A number of fires in buildings where insulated panels have been used extensively in the fabric of the building have highlighted the particular dangers that may be associated with this form of construction, i.e. where the fabric of the building can contribute to the fire hazards. In a fire the following may occur:

• early buckling and falling away of the facing materials;
• burning of the combustible insulating material;
• production of large quantities of dense, toxic smoke;
• rapid heat generation;
• early loss of structural strength can result if the system has not been properly designed, and this can lead to the collapse of the wall, partition or ceiling;
• there may be cavities in older buildings where the panels are used as an internal envelope, enabling fire to spread unnoticed and possibly unchecked by fire barriers.

Once installed it is difficult to identify the core material of a panel and its potential fire hazard. The following best practise can help you reduce risks associated with insulated panels.

Do not install heating appliances, such as ovens, against the panels. Operate a clear distance policy for cooking systems.

• Control ignition sources that are adjacent to, or penetrating the panels.
• Control hot working.
• Check for damage to heater tapes used to prevent ice build-up at doors.
• Do not store highly combustible materials against panels or allow rubbish to collect against panels.
• Have damaged panels or sealed joints repaired immediately and make sure that jointing compounds or gaskets used around the edges of the panels are in good order.
• Check where openings have been made for doors, windows, cables and ducts to ensure that these have been effectively sealed and the inner core has not been exposed.
• Check that there has been no mechanical damage and repair any that has occurred, e.g. caused by mobile equipment such as fork lift trucks.
• Ensure that any loads, such as storage and equipment, are only supported by panels which have been designed and installed to perform this function.
• Check that the inner and outer skins are adhering tightly to the core.
• Ensure that the panels are correctly secured to the structure or are designed to be independently structurally secure. One solution is to ensure the retaining brackets bolt the panel to a support frame through the outer and inner skins;
• Ensure large roof cavities are appropriately protected, e.g. escape routes are clear, signed and have limited travel distance, and fire warning systems are audible.

The use of combustible panels in areas of buildings with a high life risk, e.g. where large numbers of people are present, should be carefully considered. Your fire risk assessment may need to be revised to ensure that any increased risk resulting from this type of construction is considered.

The potential for fire development involving mineral fibre cores is less than that for panels containing polymeric cores. Therefore, in areas where there is considerable life risk, it may be appropriate to consider replacing combustible panels, providing a fire suppression system or installing non-combustible fire breaks within or between the panels at suitable intervals.

Insulated core panels should be installed by a competent person in accordance with industry guidance. Guidance on the design, construction, specification and fire management of insulated core panels has been published by the International Association of Cold Storage Contractors.

Restricting the spread of fire and smoke

To reduce the risk to people if there is a fire, you need to consider how to control or restrict the spread of fire and smoke. The majority of people who die in fires are overcome by the smoke and gases. It is important ensure that, in the event of fire, the rate of fire growth is restricted in its early stages. It should also be noted that most measures which restrict the rate of fire growth in its early stages will also serve to restrict the fire spread in its later stages.