The best correlation between the yields of the major toxicants in fire smoke and the fire condition is obtained by expressing the ventilation in terms of the equivalence ratio, phi. Phi meters allow this fuel-air equivalence ratio to be determined during a large-scale fire test. The original design used a platinum catalyst, a large furnace, and required pure oxygen. This work aimed to make a simple, low-cost device which could monitor the equivalence ratio during a large-scale fire test. The current design produces the same quality of measurement with a much smaller footprint and throughput. Benefits include enhanced portability, reduction in sample gas cleaning and drying requirements and lower cost. The work showed that normal furnace components (alumina and silica) provide suitably catalytic surfaces at 900 °C eliminating the requirement for platinum catalysts and the use of pure oxygen. The ISO/TS 19700 steady state tube furnace (SSTF) was used to validate the phi meter measurements as it can both pre-set and independently quantify the equivalence ratio during a test. Long sample collection times were overcome with a larger sampling pump and effluent being split between the phi meter furnace and the exhaust. It is hoped that this simpler, optimized apparatus will encourage more widespread use and lead to better prediction of smoke toxicity.

Polyurethane is used extensively in the furniture industry, primarily in beds and sofas. There is a significant volume of research pertaining to the flammability of polyurethane materials, but very little regarding smoke toxicity. Given toxic fire effluents are a primary cause of injury and fatalities, more work needs to be done to test the toxicity of polyurethane materials and the fire retardants they are coated/bound with. The aim of the review is to provide a comprehensive analysis of the decomposition of polyurethane and discuss the development and application of modern fire retardants and their effect on smoke toxicity. This work then provides discussion on the challenges faced when attempting to quantify the toxicity of the effluent produced during combustion. Future work should aim to reduce the toxicity and flammability of polyurethane simultaneously by; reducing the pyrolysis of the polymer, preventing the escape of volatile products, reducing radicals within the system and lowering the temperature of the system. Before this can be achieved, a better understanding of smoke toxicity and the ability to test materials is needed.

The steady state tube furnace (SSTF) (ISO/TS 19700) was used to assess the effects altering the reaction zone of a flame had on smoke toxicity measurements. The gas inlet of the apparatus was modified to allow for a mixture of nitrogen and air to be introduced into the system. The volume of air used in each test remained at 2 L min-1 , and additional volumes of nitrogen were varied between tests altering the total volume of gas used in the primary gas inlet. The chosen conditions were representative of under-ventilated flaming by using a restricted oxygen environment. The research shows that the increase in volume flow of gas over a sample increased the smoke toxicity of the materials tested (CO and HCN). When increasing the volume of the primary air-flow through the tube furnace, the flow causes thinning of the flame zone in the apparatus and results in gaseous species spending less time in the reaction zone, resulting in less time available for chemical reactions to occur. This resulted in less complete combustion occurring, and hence an increased yield of measured products of incomplete combustion (CO and HCN), and a decreased yield of products of complete combustion (CO2).

As smoke toxicity is unregulated outside of the mass transport industry, there is no set methodology for assessing smoke toxicity of construction products, like OSB, on a large-scale. This research aims to assess the novel design of a modified ISO 9705 room corner test designed for smoke toxicity quantification. Three tests conditions will be assessed to determine if restriction of ventilation is enough to force a fire to transition to under-ventilated flaming, or if the fuel loading is much more important in affecting the fire severity and fire condition. The research found that fuel loading and test geometry has more significant impact on the fire condition than restricting the ventilation. While imposing restrictions on the test rooms ventilation did increase the equivalence ratio, it was not sufficient enough to force the transition into under-ventilated flaming. The addition of a door to the test room did not force the fire to transition to under-ventilated flaming. When doubling the fuel loading, there was sufficient fuel for the fire to transition to under-ventilated flaming. This research has provided the experimental methodologies to assess smoke toxicity at a range of ventilation conditions on a large-scale.

A significant amount of data is available for bench-scale fire assessments. However, there is little surrounding large-scale tests and even less so for bench-to-large scale comparisons. Large-scale tests require more material, time and preparation, making them more expensive than bench-scale assessments. However, large-scale testing is an essential component to bench-scale fire testing. The bench-scale tests must be representative of both large-scale and real fire behaviour to provide an insight into how a material or product will behave in the event of a fire during its end use application. The few existing studies reviewed in this study show more guidance and data is needed, especially on a large-scale. Unfortunately, the data that is presented is done so in an inconsistent manner using various means of presentation, statistical analysis, and modelling that doesn’t show clear comparisons between bench and large scale. Currently, no bench-scale method shows good agreement with large-scale fire behaviour. Overall, there is a need for more large-scale testing and data for direct comparisons to be made.