What influences a building fire?

Wormald's Barry Lee, after 50 years in the industry, raises some current issues regarding construction and fire that often remain unknown.

In many instances there are avoidable elements that contribute to the ignition or severity of a fire and one serious factor can be the type of construction used in a building.

Sandwich panel construction is a common style of construction, used particularly in the manufacturing and storage industry. Sandwich panels have been found to be highly flammable and add to the severity to a fire once it has ignited. Sandwich panels can be safely used in a building only if adequate fire safety systems are installed to protect the building, its occupants and its contents.

Building regulators need to be aware of the fire hazards associated with sandwich panels and reflect this in building regulations. Additionally, Australian Standards should look to adopt overseas fire testing methods on sandwich panels, with combustible cores, to determine how they will perform under actual conditions.

Businesses need to be aware of the hazards of sandwich panel construction in order to protect the livelihood of the company and their staff. Correct fire protection can prevent the types of fires that will be detailed further in this article.

What are sandwich panels?

Sandwich panels are a composite product comprising an outer thin rigid metal sheet (usually coated steel or aluminium alloy) either side of insulating material.

There are many attractive qualities that account for the high usage of sandwich panels. They are lightweight, quick to erect, energy efficient, aesthetically attractive and require minimal maintenance and are easy to clean. Sandwich panels are used in particular by the storage and food processing industries.

How do they affect a fire?

Despite the list of advantages, sandwich panels are highly flammable but this is generally overlooked. Sandwich panels contribute to the severity and speed of fire development, hide fire spread within the actual panels, produce large quantities of black toxic smoke, and if not secured properly, can collapse early in a fire situation.

The sandwich panels also encourage flashover, which is the sudden transition of combustible materials within a compartment to a state of substantial or complete involvement in a fire.

Sandwich panels also considerably add to fire load. Fire tests have shown that fire severity is directly proportional to the fire load. The fire load is the heat energy potential of the entire combustible contents of a building space, including furnishings, wall partitions, etc, so the panels add extra material to burn and spur the fire on.

The effects of fire

Fires that involve sandwich panel construction leave behind an immense amount of damage. The indirect costs and long-term effects on a business, including employees, suppliers and customers, is often underestimated.

After-effects include the cost of replacing structural damage, replacing produce or machinery and the loss in business turnover as a result of a company not being fully operational. Job losses can occur as can relationship problems with clients and customers if supply can not be fulfilled due to fire damage.

In 1993, two firefighters in the UK actually lost their lives fighting a factory fire which involved a building constructed of lightweight sandwich panels. In the UK and Europe it has been recognised that there is a need for a code, using the technique of fire risk management in the construction, design, specification and fire management of insulated structures.

A Melbourne Fire Report from 2001 shows that in 1998 a single-storey unsprinklered self-storage facility in Footscray had its entire contents destroyed in a fire; the estimated damage cost was $2.5 million. The storage compartments were made of polystyrene sandwich panels.

In 2001, a meat rendering plant in Queensland encountered a fire that destroyed the entire building. The building had polystyrene insulation in the walls and ceilings and it was found this assisted in the rapid spread and intensity of the fire. The cost of that fire was placed at $25 million.

What can be done to protect businesses and ensure safety?

Had circumstances been different in the described fires, damage could have been minimised and safety ensured. An automatic fire sprinkler system, which may be specially designed for cold storage facilities, is the best defence to extinguish a fire involving sandwich panels in the early stages and control the fire until the fire brigade can attend to the fire.

Other ways to assist in a fire may include smoke alarms, fire compartmentation, and smoke and heat vents.

Fires involving sandwich panel construction are of significance to the Australian insurance industry as a whole, as they have the power to make it difficult for those companies unwilling to invest in adequate fire safety systems to gain insurance.

Building regulators and manufacturers need to recognise the fire hazards that are associated with the use of sandwich panels in unsprinklered buildings to prevent or minimise serious fire damage.

Polystyrene sandwich panelling is an extremely fire hazardous material. The best way to utilise sandwich panel construction safely is by having a fire safety system installed, particularly a sprinkler system. By installing a sprinkler system this will minimise the risk of a fire spreading and will help to protect both property and people if a fire does occur.