Unwanted fires continue to account for a significant loss of life, damage to property, damage to business and damage to the environment. Meanwhile the cost of prevention and protection measures adds a substantial drain to an already struggling economy. The cost of fire is almost 1% of GDP while the cost of fire safety measures for a new building is around 2.5%. The action required to prevent such losses is expensive and may involve inappropriate or unnecessary measures. To address specific threats, such as fires in public buildings, or resulting from terrorism it is essential to improve our understanding of the behaviour of unwanted fires particularly the transition to under-ventilated flaming and the rapid increase in toxicity. Most fire deaths and most fire injuries actually result from inhalation of toxic gases. If reliable means of predicting toxic product yields in real-scale fires were developed, lives could be saved and costs reduced. Combustion toxicity is generally underestimated in small-scale tests, and is highly dependent on fire conditions. The project will quantify combustion toxicity using the unique design of the steady state tube furnace (SSTF) (ISO TS 19700), which allows full-scale fire behaviour, under different fire conditions, to be replicated on a small scale. Crucially, it will also use UCLan's new custom-designed Large Instrumented Fire Enclosure (LIFE) facility based at Lancashire Fire and Rescue Service's Training Centre to investigate the relationship between scales as a function of temperature and ventilation condition. This apparatus is based on a half-scale ISO 9705 room with corridor, as a reference scenario for generation of toxic products from fire, in order to validate bench-scale (ISO 19700) data for use in engineering hazard calculations, and provide crucial information on the behaviour of under-ventilated fires. The outcomes of the work have direct relevance to the fire safety engineering community (in order to predict escape times based on fire toxicity and visual obscuration) while understanding the transition to highly toxic, under-ventilated fires will save lives, and reduce costs. It will also provide materials scientists with the tools to optimise products for lower fire toxicity suitable for high risk application such as mass transport or high rise buildings.