Passive protection
October 1st 2005

Richard Price, technical manager of Eurobond explains how to design fire safety into warehouses by using incombustible internal walls

Earlier this year, a dramatic warehouse fire adjacent the Dartford Tunnel brought the effect of fire to public awareness like never before. Not only was the warehouse totally destroyed but the infrastructure of East London was disrupted for several days because of billowing smoke which closed the M25.

The food industry is particularly vulnerable to disastrous fires. Several major ones have occurred recently - a garlic bread factory in Hull which was totally destroyed, a bacon factory, a crisps factory plus major fires at well-known names like Trebor Bassett and the Branston Pickle works in Suffolk. It is a sobering thought that 1 in 3 companies go out of business as a result of a major fire.

The upcoming Fire Reform Act - or Regulatory Reform Fire Safety Order, to give its full name - will have a major effect on fire safety design in buildings. Soon, designers, contractors, owners and occupiers will have responsibilities which they will ignore at their peril.

Designing against fire

Fire risk can be dramatically minimised when products ‘fit for purpose’ are specified; for this greater understanding and education are necessary. For example, it is obviously better and more effective to design-in non-combustible products from the beginning rather than rely on applied precautions and cautious building management to lower the fire risk.

One of the problems for the building industry is terminology and the claims of manufacturers. With the threat of prison and other dire consequences, the specifier must begin to look much closer at the ‘small print’. He or she must take a view and make quite sure than materials specified are indeed ‘fit for purpose’.

Nowhere is this more critical, and the subject of much debate, than in the specification of internal firewalls. For example, many factories are built with walls that have oil-based foam cores (such as PIR, PUR and EPS) and are believed to be noncombustible.

As many fires have proved, these are combustible, are not smokeproof and therefore hazardous. To make them non-combustible, stitching of panel joints, fixing cover strips and the use of intumescent seals are required for foamcored panels so that an acceptable level of fire resistance is achieved. Logically, this will make the system more expensive to purchase and install.

Conversely, by their very nature, compartmentation walls with mineral fibre cores offer greater ‘peace of mind’ because they are non-combustible, smoke-safe and provide excellent ‘passive’ fire protection because of their high levels of inherent fire resistance.

Insurance

The Association of Insurers issue Briefing notes which deal with risk management; one in particular emphasises the benefits of fire resisting compartment walls.

Compartmentation reduces the spread of fire, it restricts the passage of smoke, helping to save lives and reduce damage to stored goods and production areas. The main applications in the LPC Design Guide for the Fire Protection of Buildings are from 90 to 240 minutes fire resistance (both integrity and insulation). This tends to restrict the choice to sandwich panel systems with high density rock fibre mineral wool cores. No current foam-based cored panels (such as PIR) are able to deliver this level of fire resistance. Equally important is the construction of external walls - such as envelope for industrial buildings and warehouses - which are highly vulnerable to attacks of arson.

Case studies

Clearly, it is not necessary to reinvent the wheel. Studies of actual fires, together with insurer, Fire Brigade or customer analysis of what actually happened, is all that is necessary to ensure that that the right construction choice is made.

For example, the Firemaster system comprises wall panel systems which are load-bearing and provide up to 240 minutes fire resistance because of their construction and non-combustible core of mineral fibre (Rockwool).

It is significant that in some of the recent food factory fires mentioned previously, the system was picked out for special praise by the Fire Brigade. In at least two of the fires, including one where Rockwool and PIR foam cored walls were installed, management has decreed that only the former should be used in future.

The Grampian Foods fire is another example because the 150mm thick Firemaster panels in a small 100m2 room contained the fire. The Norfolk Fire Brigade, who also tackled the fire at Kettle Foods in Norwich, was very complimentary about the way the internal walls with their mineral fibre core performed. Often firefighters will not bother to fight a fire when the core material is polystyrene or other material.

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