Most unwanted fires are fuelled by polymeric materials long chains, with up to a million links in each chain, so the process of a fire starting involves breaking the chain into molecules which are small enough to vaporise, then react with oxygen, producing free radicals and releasing lots of heat - resulting in a flame. The reactions in a flame are billions of times faster than normal chemical reactions, and in the simple process of lighting a match, cellulose polymer chains are broken into small molecules, which are then oxidised to carbon dioxide and water! Fire retardants work by interfering with these processes. Some increase the amount of char formation, so the fuel is protected by a layer which won't vaporise easily. Others produce a swollen protective layer on the surface of the polymer, stopping the heat being able to break the chains.

A third group interfere with the free radical processes in flames, resulting in more products of incomplete combustion, including carbon monoxide, hydrocarbons and smoke. All are a testament to the ingenuity of chemists in creating a wonderful “box of tricks” without interfering too much with the useful properties of the plastic. Unfortunately, as plastics, and so fire retardants, have become more and more widespread, a number of problems have become associated with their use. Many of the original flame retardants are gas phase quenchers. Not only are they toxic, but also stable enough to persist in the environment. They have been found in pristine regions, such as the Arctic ice, and cause harm in wild birds, whales and porpoises. The gas phase flame retardants also increase the toxicity of the smoke when they burn. Almost all fire retardants cause problems for recyclers during end-of-life processing.

Fire retardants are only added to meet regulatory requirements, so can allow more flammable polymers to be used in high-risk situations. Most fire deaths and most fire injuries result from inhalation of toxic smoke. The team at UCLan are world-leading in understanding the generation, quantification and hazards of toxic smoke. While a single match burning will only produce carbon dioxide and water, a larger fire, particularly indoors, will quickly grow to become ventilation-controlled and because it cannot get enough oxygen will produce large amounts of deadly carbon monoxide, smoke, which stops people being able to see how to escape, and other partly oxygenated hydrocarbons which make it difficult to breathe. We have shown the effect of ventilation and fire retardants on the toxicity of smoke.

Recent publications:

Burning behaviour of rainscreen façades. (2021) Journal of Hazardous Materials, 403. Art no. 123894.
Smoke toxicity of rainscreen façades. (2021) Journal of Hazardous Materials, 403. Art no. 123694.
A Critical Appraisal of the UK’s Regulatory Regime for Combustible Façades. (2020) Fire Technology, 57. pp. 261-290.
Fire behaviour of modern façade materials – Understanding the Grenfell Tower fire. (2019) Journal of Hazardous Materials, 368. pp. 115-123.
Fire performance of sandwich panels in a modified ISO 13784-1 small room test: the influence of increased fire load for different insulation materials. (2018) Fire Technology, 54 (4). pp. 819-852.
Flame retardants in UK furniture increase smoke toxicity more than they reduce fire growth rate. (2018) Chemosphere, 196. pp. 429-439.

Large scale burn facilities

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