22 September 2005 10:00am

Hot Topic

Fire Engineering, Fire Safety, Industry News, Non-combustible, PIR, Toxic Smoke

The increased vulnerability of people inside a hospital building certainly heightens a building owner’s duty of care and, as such, a building’s resistance to fire is key. Eurobond looks to why specifiers are now being directed towards non-combustible cored products, when choosing composite panels.

In 2004 there were 2,184 fires in UK hospitals resulting in 4 deaths and 109 non-fatal casualties. Fire safety has always been a key consideration in hospital design, with limiting fire spread the main concern, particularly in the early stages when horizontal evacuation is in operation. This responsibility will soon become even more acute, with the introduction of the new Fire Safety Order this October.

The Fire Safety Order has for the first time officially recognised the risks associated with combustible composite panels. It states “The potential for fire development involving mineral fibre cores is less than that for panels containing polymeric cores. Therefore, in areas where this is a considerable life risk, it may be appropriate to consider replacing combustible composite panels.”

The draft of the NHS FireCode goes even further, stating, “Selecting the appropriate insulated core products for internal walls or partitions, or for external cladding material is vital for patient and building occupant safety…Wherever possible cladding with a non-combustible core should be used.”

So why is the distinction between combustible and non-combustible cores now such a focus? It all comes down to some confusion in the market as to the level of fire protection that is actually achieved by the different types of composite panel available.

When specifying products, references to ‘fireproof’, ‘firesafe’, ‘self-extinguishing’ and ‘fire retarding’ are often interpreted as the equivalent of ‘non-combustible’, but this is not the case.

Sandwich panels that have been manufactured using a non-combustible core such as mineral wool won’t ignite in the event of a fire, as the material is made of stone and will not burn. The composite panels therefore contribute no additional risk of fire spread or smoke.

The same can’t be guaranteed for foam cored composite panels, where the challenge is in ensuring that a fire won’t reach the core via the panel joints. This can only be reasonably secured against with the use of cover strip flashings, intumescent seals and physical stitching of the internal joints, and this needs to be done on both sides of the panel to achieve symmetrical fire resistance. This is often not acceptable from an installation or an aesthetic point of view and the system is also open to the risks posed by inadequate system specification, faulty workmanship or poor maintenance.

Even if the full system has been correctly installed, in the event of extreme heat the steel composite panels will bend, and the joints will be exposed – it is then that the foam core is at risk of ignition.

According to BRUFMA (British Urethane Manufacturers Association), “Any combustible material will ignite if heated to a sufficiently high temperature in air, in the case of PIR/PUR foams this would need to be about 450°C”. The risk of fire spread is therefore very real, if combustible cored panels are in use.

In most cases of fire it’s not actually the flames, but smoke and toxic fumes that cause injury or death. The most common identified cause of death or injury in a fire is being overcome by gas or smoke, this accounting for 53% of all fire deaths and 34% of all non fatal casualties in 2004.

BRUFMA also confirms that “all organic materials evolve toxic decomposition products when burning” and when PUR or PIR core-based sandwich panels ignite they will give off large volumes of black toxic smoke. Recent independent fire tests underline this. A sample of PIR was ignited and the toxic gases in the smoke analysed. The concentration of hydrogen cyanide (HCN) was 72 parts per million (ppm).

The American National Institute for Occupational Safety and Health define and list the ‘Immediately Dangerous to Health’ (IDLH) level for HCN as 50 ppm. For carbon monoxide (CO) the level in the test was 1533ppm compared to an IDLH of 1200.

In the same tests mineral wool did not ignite and produced no smoke. However, its resin binder gave rise to a HCN level of only 5ppm – a tenth of the dangerous level.

When specifying architectural composite wall panels there are many factors to take into account. Aesthetics, design flexibility and ease of installation are all elements that require lengthy consideration, but a panel’s true fire and smoke performance is often just taken as a given.

With the new Fire Safety Order moving fire safety firmly up the agenda, now more than ever specifiers need to consider the contribution any materials they specify may have on fire spread or smoke. Therefore our message is simple – when it comes to fire why take the risk? Only non-combustible panels offer true levels of fire and smoke resistance.